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| www.ti.com DAC7574 SLAS375 - JUNE 2003 QUAD, 12-BIT, LOW-POWER, VOLTAGE OUTPUT, I C INTERFACE DIGITAL-TO-ANALOG CONVERTER 2 FEATURES * * * * * * * * * * * * Micropower Operation: 600 A at 5 V VDD Power-On Reset to Zero +2.7 V to +5.5 V Analog Power Supply 12-Bit Monotonic I2CTM Interface Up to 3.4 Mbps Data Transmit Capability On-Chip Output Buffer Amplifier, Rail-to-Rail Operation Double-Buffered Input Register Address Support for up to Four DAC7574s Synchronous Update Support for up to 16 Channels Operation From -40C to 105C Small 10 Lead MSOP Package DESCRIPTION The DAC7574 is a low-power, quad channel, 12-bit buffered voltage output DAC. Its on-chip precision output amplifier allows rail-to-rail output swing to be achieved. The DAC7574 utilizes an I2C compatible two wire serial interface supporting high-speed interface mode with address support of up to four DAC7574s for a total of 16 channels on the bus. The DAC7574 uses VDD and GND to set the output range of the DAC. The DAC7574 incorporates a power-on-reset circuit that ensures that the DAC output powers up at zero volts and remains there until a valid write takes place to the device. The DAC7574 contains a power-down feature, accessed via the internal control register, that reduces the current consumption of the device to 200 nA at 5 V. The low power consumption of this part in normal operation makes it ideally suited to portable battery operated equipment. The power consumption is less than 3mW at VDD = 5 V reducing to 1 W in power-down mode. The DAC7574 is available in a 10-lead MSOP package. APPLICATIONS * * * * * Process Control Data Acquisition Systems Closed-Loop Servo Control PC Peripherals Portable Instrumentation VDD Data Buffer A DAC Register A DAC A VOUTA VOUTB VOUTC Data Buffer D 14 DAC Register D DAC D VOUTD SCL SDA I2C Block 8 Buffer Control Register Control Power-Down Control Logic Resistor Network A0 A1 GND I2C is a trademark of Philips Corporation. Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright (c) 2003, Texas Instruments Incorporated DAC7574 SLAS375 - JUNE 2003 www.ti.com This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. PACKAGE/ORDERING INFORMATION PRODUCT PACKAGE PACKAGE DRAWING NUMBER DGS SPECIFICATION TEMPERATURE RANGE -40C TO +105C PACKAGE MARKING D774 ORDERING NUMBER DAC7574IDGS DAC7574IDGSR TRANSPORT MEDIA DAC7574 10-MSOP 80 Piece Tube 2500 Piece Tape and Reel DGS PACKAGE (TOPVIEW) PIN NAME VOUTA VOUTB GND VOUTC VOUTD SCL SDA VDD A0 A1 PIN DESCRIPTIONS DESCRIPTION Analog output voltage from DAC A Analog output voltage from DAC B Ground reference point for all circuitry on the part Analog output voltage from DAC C Analog output voltage from DAC D Serial clock input Serial data input and output Analog voltage supply input Device address select - I2C Device address select - I2C VOUTA VOUTB GND 1 2 3 DAC7574 10 A1 9 A0 8 VDD 7 SDA 6 SCL 1 2 3 4 5 6 7 8 9 10 VOUTC 4 VOUTD 5 ABSOLUTE MAXIMUM RATINGS (1) VDD to GND Digital input voltage to GND VOUT to GND Operating temperature range Storage temperature range Junction temperature range (TJ max) Power dissipation: Thermal impedance (JA) Thermal impedance (JC) Lead temperature, soldering: Vapor phase (60s) Infrared (15s) (1) -0.3 V to +6 V -0.3 V to VDD + 0.3 V -0.3 V to VDD + 0.3 V - 40C to +105C - 65C to +150C +150C 270C/W 77C/W 215C 220C Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to absolute maximum conditions for extended periods may affect device reliability. 2 www.ti.com DAC7574 SLAS375 - JUNE 2003 ELECTRICAL CHARACTERISTICS VDD = 2.7 V to 5.5 V, RL = 2 k to GND; CL = 200 pF to GND; all specifications -40C to +105C, unless otherwise specified. PARAMETER STATIC PERFORMANCE (1) Resolution Relative accuracy Differential nonlinearity Zero-scale error Full-scale error Gain error Zero code error drift Gain temperature coefficient OUTPUT CHARACTERISTICS (2) Output voltage range Output voltage settling time (full scale) Slew rate DC crosstalk (channel-to-channel) AC crosstalk (channel-to-channel) Capacitive load stability Digital-to-analog glitch impulse Digital feedthrough DC output impedance Short-circuit current Power-up time VDD= 5 V VDD= 3 V Coming out of power-down mode, VDD= +5 V Coming out of power-down mode, VDD= +3 V LOGIC INPUTS (2) Input current VIN_L, Input low voltage VIN_H, Input high voltage Pin Capacitance POWER REQUIREMENTS VDD IDD(normal operation), including reference current IDD@ VDD=+3.6V to +5.5V IDD@ VDD =+2.7V to +3.6V IDD (all power-down modes) IDD@ VDD=+3.6V to +5.5V IDD@ VDD =+2.7V to +3.6V POWER EFFICIENCY IOUT/IDD ILOAD= 2 mA, VDD= +5 V 93% VIH= VDD and VIL=GND VIH= VDD and VIL=GND 0.2 0.05 1 1 A A Excluding load current VIH= VDD and VIL=GND VIH= VDD and VIL=GND 600 550 900 750 A A 2.7 5.5 V VDD= 3 V 0.7xVDD 3 1 0.3xVDD A V V pF 1 kHz Sine Wave RL= RL= 2 k 1 LSB change around major carry RL = ; 0 pF < CL < 200 pF RL = ; CL = 500 pF 0 8 12 1 0.25 -100 470 1000 12 0.3 1 50 20 2.5 5 VDD 10 V s s V/s LSB dB pF pF nV-s nV-s mA mA s s 7 3 Specified monotonic by design 5 -0.15 TEST CONDITIONS MIN 12 8 1 20 1.0 1.0 TYP MAX UNITS Bits LSB LSB mV % of FSR % of FSR V/C ppm of FSR/C (1) (2) Linearity tested using a reduced code range of 48 to 4047; output unloaded. Specified by design and characterization, not production tested. 3 DAC7574 SLAS375 - JUNE 2003 www.ti.com ELECTRICAL CHARACTERISTICS (continued) VDD = 2.7 V to 5.5 V, RL = 2 k to GND; CL = 200 pF to GND; all specifications -40C to +105C, unless otherwise specified. PARAMETER TEMPERATURE RANGE Specified performance -40 +105 C TEST CONDITIONS MIN TYP MAX UNITS TIMING CHARACTERISTICS VDD = 2.7 V to 5.5 V, RL = 2 k to GND; all specifications -40C to +105C, unless otherwise specified. SYMBOL PARAMETER TEST CONDITIONS Standard mode fSCL SCL clock frequency Fast mode High-Speed Mode, CB = 100 pF max High-speed mode, CB = 400 pF max tBUF Bus free time between a STOP and START condition Hold time (repeated) START condition Standard mode Fast mode Standard mode tHD; tSTA Fast mode High-speed mode Standard mode tLOW LOW period of the SCL clock Fast mode High-speed mode, CB = 100 pF max High-speed mode, CB = 400 pF max Standard mode tHIGH HIGH period of the SCL clock Fast mode High-Speed Mode, CB = 100 pF max High-speed mode, CB = 400 pF max Standard mode tSU; tSTA Setup time for a repeated START condition Fast mode High-speed mode Standard mode tSU; tDAT Data setup time Fast mode High-speed mode Standard mode tHD; tDAT Data hold time Fast mode High-speed mode, CB = 100 pF max High-speed mode, CB = 400 pF max Standard mode tRCL Rise time of SCL signal Fast mode High-speed mode, CB = 100 pF max High-speed mode, CB = 400 pF max Rise time of SCL signal after a repeated START condition and after an acknowledge BIT Standard mode Fast mode High-speed mode, CB = 100 pF max High-speed mode, CB = 400 pF max Standard mode tFCL Fall time of SCL signal Fast mode High-speed mode, CB = 100 pF max High-speed mode, CB = 400 pF max 4 4.7 1.3 4.0 600 160 4.7 1.3 160 320 4.0 600 60 120 4.7 600 160 250 100 10 0 0 0 0 20 x 0.1CB 20 x 0.1CB 10 20 20 x 0.1CB 20 x 0.1CB 10 20 20 x 0.1CB 20 x 0.1CB 10 20 3.45 0.9 70 150 1000 300 40 80 1000 300 80 160 300 300 40 80 MIN TYP MAX 100 400 3.4 1.7 UNITS kHz kHz MHz MHz s s s ns ns s s ns ns s ns ns ns s ns ns ns ns ns s s ns ns ns ns ns ns ns ns ns ns ns ns ns ns tRCL1 www.ti.com DAC7574 SLAS375 - JUNE 2003 TIMING CHARACTERISTICS (continued) VDD = 2.7 V to 5.5 V, RL = 2 k to GND; all specifications -40C to +105C, unless otherwise specified. SYMBOL PARAMETER TEST CONDITIONS Standard mode tRDA Rise time of SDA signal Fast mode High-speed mode, CB = 100 pF max High-speed mode, CB = 400 pF max Standard mode tFDA Fall time of SDA signal Fast mode High-speed mode, CB = 100 pF max High-speed mode, CB = 400 pF max Standard mode tSU; tSTO Setup time for STOP condition Capacitive load for SDA and SCL Pulse width of spike suppressed Noise margin at the HIGH level for each connected device (including hysteresis) Noise margin at the LOW level for each connected device (including hysteresis) Fast mode High-speed mode Standard mode Fast mode High-speed mode Standard mode Fast mode High-speed mode 0.1 VDD V 0.2 VDD V Fast mode High-speed mode CB tSP MIN 20 x 0.1CB 20 x 0.1CB 10 20 20 x 0.1CB 20 x 0.1CB 10 20 4.0 600 160 400 50 10 TYP MAX 1000 300 80 160 300 300 80 160 UNITS ns ns ns ns ns ns ns ns s ns ns pF ns ns VNH VNL 5 DAC7574 SLAS375 - JUNE 2003 www.ti.com TYPICAL CHARACTERISTICS At TA = +25C, unless otherwise noted. LINEARITY ERROR AND DIFFERENTIAL LINEARITY ERROR vs DIGITAL INPUT CODE 8 6 4 2 0 -2 -4 -6 -8 1.0 DLE - LSB 0.5 0.0 - 0.5 - 1.0 0 512 1024 1536 2048 2560 3072 3584 Digital Input Code DLE - LSB Channel A LE - LSB LE - LSB VDD = 5 V 8 6 4 2 0 -2 -4 -6 -8 1.0 0.5 0.0 - 0.5 - 1.0 0 512 1024 1536 2048 2560 3072 3584 Digital Input Code LINEARITY ERROR AND DIFFERENTIAL LINEARITY ERROR vs DIGITAL INPUT CODE Channel B VDD = 5 V Figure 1. Figure 2. LINEARITY ERROR AND DIFFERENTIAL LINEARITY ERROR vs DIGITAL INPUT CODE 8 6 4 2 0 -2 -4 -6 -8 1.0 DLE - LSB 0.5 0.0 - 0.5 - 1.0 Channel D LE - LSB VDD = 5 V LINEARITY ERROR AND DIFFERENTIAL LINEARITY ERROR vs DIGITAL INPUT CODE 8 6 4 2 0 -2 -4 -6 -8 1.0 DLE - LSB 0.5 0.0 - 0.5 - 1.0 0 512 1024 1536 2048 2560 3072 3584 Digital Input Code Channel C LE - LSB VDD = 5 V 0 512 1024 1536 2048 2560 3072 3584 Digital Input Code Figure 3. Figure 4. LINEARITY ERROR AND DIFFERENTIAL LINEARITY ERROR vs DIGITAL INPUT CODE 8 6 4 2 0 -2 -4 -6 -8 1.0 DLE - LSB 0.5 0.0 - 0.5 - 1.0 Channel B LE - LSB VDD = 2.7 V LINEARITY ERROR AND DIFFERENTIAL LINEARITY ERROR vs DIGITAL INPUT CODE 8 6 4 2 0 -2 -4 -6 -8 1.0 DLE - LSB 0.5 0.0 - 0.5 - 1.0 0 512 1024 1536 2048 2560 3072 3584 Digital Input Code Channel A LE - LSB VDD = 2.7 V 0 512 1024 1536 2048 2560 3072 3584 Digital Input Code Figure 5. Figure 6. 6 www.ti.com DAC7574 SLAS375 - JUNE 2003 TYPICAL CHARACTERISTICS (continued) At TA = +25C, unless otherwise noted. LINEARITY ERROR AND DIFFERENTIAL LINEARITY ERROR vs DIGITAL INPUT CODE 8 6 4 2 0 -2 -4 -6 -8 1.0 DLE - LSB 0.5 0.0 - 0.5 - 1.0 0 512 1024 1536 2048 2560 3072 3584 Digital Input Code DLE - LSB Channel C LE - LSB LE - LSB VDD = 2.7 V 8 6 4 2 0 -2 -4 -6 -8 1.0 0.5 0.0 - 0.5 - 1.0 LINEARITY ERROR AND DIFFERENTIAL LINEARITY ERROR vs DIGITAL INPUT CODE Channel D VDD = 2.7 V 0 512 1024 1536 2048 2560 3072 3584 Digital Input Code Figure 7. Figure 8. ZERO-SCALE ERROR vs TEMPERATURE 15 VDD = 2.7 V Zero-Scale Error - mV ZERO-SCALE ERROR vs TEMPERATURE 20 VDD = 5 V Zero-Scale Error - mV 15 CH C CH D 10 CH B CH A 10 CH C CH D 5 CH B CH A 5 - 40 - 10 20 50 80 TA - Free - Air Temperature - C 0 - 40 - 10 20 50 80 TA - Free - Air Temperature - C Figure 9. Figure 10. FULL-SCALE ERROR vs TEMPERATURE 20 VDD = 2.7 V Full-Scale Error - mV FULL-SCALE ERROR vs TEMPERATURE 30 VDD = 5 V 25 Full-Scale Error - mV CH A 20 CH D 15 10 CH B 5 0 - 40 - 10 20 50 80 TA - Free - Air Temperature - C 0 - 40 CH C 15 CH A 10 CH C CH D 5 CH B - 10 20 50 80 TA - Free - Air Temperature - C Figure 11. Figure 12. 7 DAC7574 SLAS375 - JUNE 2003 www.ti.com TYPICAL CHARACTERISTICS (continued) At TA = +25C, unless otherwise noted. SINK CURRENT CAPABILITY AT NEGATIVE RAIL 0.150 Typical For All Channels VOUT - Output Voltage - V VOUT - Output Voltage - V 0.125 0.100 0.075 0.050 0.025 DAC Loaded With 000H 0.000 0 1 2 3 4 5 ISINK - Sink Current - mA 5.30 0 VDD = 2.7 V VDD = 5.5 V 5.45 5.50 SOURCE CURRENT CAPABILITY AT POSITIVE RAIL Typical For All Channels 5.40 5.35 DAC Loaded With FFFH VDD = 5.5 V 1 2 3 4 5 ISOURCE - Source Current - mA Figure 13. Figure 14. SUPPLY CURRENT vs DIGITAL INPUT CODE 800 700 IDD - Supply Current - A 600 500 400 300 200 100 0 All Channels Powered, No Load 0 512 1024 1536 2048 2560 3072 3584 4096 Digital Input Code VDD = 2.7 V VDD = 5.5 V SOURCE CURRENT CAPABILITY AT POSITIVE RAIL 2.7 Typical For All Channels VOUT - Output Voltage - V 2.6 2.5 2.4 DAC Loaded With FFFH VDD = 2.7 V 2.3 0 1 2 3 4 5 ISOURCE - Source Current - mA Figure 15. Figure 16. SUPPLY CURRENT vs SUPPLY VOLTAGE 700 650 IDD - Supply Current - A 600 550 500 450 400 350 300 250 200 80 110 2.7 All DACs Powered, No Load 3.1 3.5 3.9 4.3 4.7 5.1 5.5 SUPPLY CURRENT vs TEMPERATURE 700 IDD - Supply Current - A 600 VDD = 5.5 V 500 400 300 200 100 All Channels Powered, No Load 0 - 40 - 10 20 50 TA - Free - Air Temperature - C VDD = 2.7 V VDD - Supply Voltage - V Figure 17. Figure 18. 8 www.ti.com DAC7574 SLAS375 - JUNE 2003 TYPICAL CHARACTERISTICS (continued) At TA = +25C, unless otherwise noted. SUPPLY CURRENT vs LOGIC INPUT VOLTAGE 1200 IDD - Supply Current - A 1000 800 VDD = 5.5 V 600 400 VDD = 2.7 V 200 0 1 2 3 4 5 0 Frequency TA = 25C SCL Input (All Other Inputs = GND) 2000 HISTOGRAM OF CURRENT CONSUMPTION VDD = 5 V 1500 1000 500 500 520 540 560 580 600 620 640 660 680 700 720 740 IDD - Current Consumption - A VLogic - Logic Input Voltage - V Figure 19. Figure 20. EXITING POWER-DOWN MODE 6 5 4 3 2 1 0 -1 VDD = 5 V Powerup to Code 4000 HISTOGRAM OF CURRENT CONSUMPTION 2000 VDD = 2.7 V 1500 Frequency VOUT - Output Voltage - V 400 420 440 460 480 500 520 540 560 580 600 620 IDD - Current Consumption - A 1000 500 0 Time (2 s/div) Figure 21. Figure 22. OUTPUT GLITCH (Worst Case) VOUT - Output Voltage - V (20 mV/div) 4.74 4.72 4.70 4.68 4.66 4.64 4.62 4.60 4.58 4.56 Time (15 s/div) VDD = 5 V Code EFFH to F00H to EFFH (Glitch Occurs Every N*256 Code Boundary) OUTPUT GLITCH (Mid-Scale) VOUT - Output Voltage - V (20 mV/div) 2.56 2.54 2.52 2.50 2.48 2.46 2.44 2.42 2.40 Time (15 s/div) VDD = 5 V Code 7FFH to 800H to 7FFH (Glitch Occurs Every N*256 Code Boundary) Figure 23. Figure 24. 9 DAC7574 SLAS375 - JUNE 2003 www.ti.com TYPICAL CHARACTERISTICS (continued) At TA = +25C, unless otherwise noted. ABSOLUTE ERROR 24 20 Output Error - mV 16 12 8 4 0 0 512 1024 1536 2048 2560 3072 3584 Channel D Output Channel C Output Channel B Output VDD = 5 V TA = 25C Output Error - mV Channel A Output 18 14 10 6 2 ABSOLUTE ERROR VDD = 2.7 V TA = 25C Channel A Output Channel B Output Channel D Output -2 -6 0 512 1024 1536 2048 Channel C Output 2560 3072 3584 Digital Input Code Digital Input Code Figure 25. Figure 26. LARGE SIGNAL SETTLING TIME 3.0 VOUT - Output Voltage - V 2.5 2.0 1.5 1.0 0.5 0.0 VDD = 2.7 V Output Loaded with 200 pF to GND 10% to 90% FSR LARGE SIGNAL SETTLING TIME 5 VOUT - Output Voltage - V 4 3 2 1 0 Time (25 s/div) VDD = 5 V Output Loaded with 200 pF to GND 10% to 90% FSR Time (25 s/div) Figure 27. Figure 28. 10 www.ti.com DAC7574 SLAS375 - JUNE 2003 THEORY OF OPERATION D/A SECTION The architecture of the DAC7574 consists of a string DAC followed by an output buffer amplifier. Figure 29 shows a generalized block diagram of the DAC architecture. VDD 50 kW 70 kW _ DAC Register Ref+ Resistor String RefGND + VOUT 50 kW Figure 29. R-String DAC Architecture The input coding to the DAC7574 is unsigned binary, which gives the ideal output voltage as: D V OUT + VDD 4096 (1) Where D = decimal equivalent of the binary code that is loaded to the DAC register; it can range from 0 to 4095. RESISTOR STRING The resistor string section is shown in Figure 30. It is basically a divide-by-2 resistor, followed by a string of resistors, each of value R. The code loaded into the DAC register determines at which node on the string the voltage is tapped off to be fed into the output amplifier by closing one of the switches connecting the string to the amplifier. Because the architecture consists of a string of resistors, it is specified monotonic. VDD To Output Amplifier GND R R R R Figure 30. Typical Resistor String Output Amplifier The output buffer is a gain-of-2 noninverting amplifiers, capable of generating rail-to-rail voltages on its output, which gives an output range of 0V to VDD. It is capable of driving a load of 2 k in parallel with 1000 pF to GND. The source and sink capabilities of the output amplifier can be seen in the typical curves. The slew rate is 1 V/s with a half-scale settling time of 8 s with the output unloaded. I2C Interface I2C is a 2-wire serial interface developed by Philips Semiconductor (see I2C-Bus Specification, Version 2.1, January 2000). The bus consists of a data line (SDA) and a clock line (SCL) with pullup structures. When the bus is idle, both SDA and SCL lines are pulled high. All the I2C compatible devices connect to the I2C bus through open drain I/O pins, SDA and SCL. A master device, usually a microcontroller or a digital signal processor, controls the bus. The master is responsible for generating the SCL signal and device addresses. The master also generates specific conditions that indicate the START and STOP of data transfer. A slave device receives and/or transmits data on the bus under control of the master device. 11 DAC7574 SLAS375 - JUNE 2003 www.ti.com THEORY OF OPERATION (continued) The DAC7574 works as a slave and supports the following data transfer modes, as defined in the I2C-Bus Specification: standard mode (100 kbps), fast mode (400 kbps), and high-speed mode (3.4 Mbps). The data transfer protocol for standard and fast modes is exactly the same, therefore they are referred to as F/S-mode in this document. The protocol for high-speed mode is different from the F/S-mode, and it is referred to as H/S-mode. The DAC7574 supports 7-bit addressing; 10-bit addressing and general call address are not supported. F/S-Mode Protocol * The master initiates data transfer by generating a start condition. The start condition is when a high-to-low transition occurs on the SDA line while SCL is high, as shown in Figure 31. All I2C-compatible devices should recognize a start condition. The master then generates the SCL pulses, and transmits the 7-bit address and the read/write direction bit R/W on the SDA line. During all transmissions, the master ensures that data is valid. A valid data condition requires the SDA line to be stable during the entire high period of the clock pulse (see Figure 32). All devices recognize the address sent by the master and compare it to their internal fixed addresses. Only the slave device with a matching address generates an acknowledge (see Figure 33) by pulling the SDA line low during the entire high period of the 9th SCL cycle. Upon detecting this acknowledge, the master knows that communication link with a slave has been established. The master generates further SCL cycles to either transmit data to the slave (R/W bit 1) or receive data from the slave (R/W bit 0). In either case, the receiver needs to acknowledge the data sent by the transmitter. So acknowledge signal can either be generated by the master or by the slave, depending on which one is the receiver. 9-bit valid data sequences consisting of 8-bit data and 1-bit acknowledge can continue as long as necessary. To signal the end of the data transfer, the master generates a stop condition by pulling the SDA line from low to high while the SCL line is high (see Figure 31). This releases the bus and stops the communication link with the addressed slave. All I2C compatible devices must recognize the stop condition. Upon the receipt of a stop condition, all devices know that the bus is released, and they wait for a start condition followed by a matching address. * * * H/S-Mode Protocol * * When the bus is idle, both SDA and SCL lines are pulled high by the pullup devices. The master generates a start condition followed by a valid serial byte containing H/S master code 00001XXX. This transmission is made in F/S-mode at no more than 400 Kbps. No device is allowed to acknowledge the H/S master code, but all devices must recognize it and switch their internal setting to support 3.4 Mbps operation. The master then generates a repeated start condition (a repeated start condition has the same timing as the start condition). After this repeated start condition, the protocol is the same as F/S-mode, except that transmission speeds up to 3.4 Mbps are allowed. A stop condition ends the H/S-mode and switches all the internal settings of the slave devices to support the F/S-mode. Instead of using a stop condition, repeated start conditions should be used to secure the bus in H/S-mode. * 12 www.ti.com DAC7574 SLAS375 - JUNE 2003 THEORY OF OPERATION (continued) SDA SDA SCL S Start Condition P Stop Condition SCL Figure 31. START and STOP Conditions SDA SCL Data Line Stable; Data Valid Change of Data Allowed Figure 32. Bit Transfer on the I2C Bus Data Output by Transmitter Not Acknowledge Data Output by Receiver Acknowledge SCL From Master S START Condition 1 2 8 9 Clock Pulse for Acknowledgement Figure 33. Acknowledge on the I2C Bus 13 DAC7574 SLAS375 - JUNE 2003 www.ti.com Recognize START or REPEATED START Condition Generate ACKNOWLEDGE Signal Recognize STOP or REPEATED START Condition P SDA MSB Address Acknowledgement Signal From Slave Sr R/W SCL S or Sr START or Repeated START Condition 1 2 7 8 9 ACK 1 2 3-8 9 ACK Sr or P Clock Line Held Low While Interrupts are Serviced STOP or Repeated START Condition Figure 34. Bus Protocol DAC7574 I2C Update Sequence The DAC7574 requires a start condition, a valid I2C address, a control byte, an MSB byte, and an LSB byte for a single update. After the receipt of each byte, DAC7574 acknowledges by pulling the SDA line low during the high period of a single clock pulse. A valid I2C address selects the DAC7574. The control byte sets the operational mode of the selected DAC7574. Once the operational mode is selected by the control byte, DAC7574 expects an MSB byte followed by an LSB byte for data update to occur. DAC7574 performs an update on the falling edge of the acknowledge signal that follows the LSB byte. Control byte needs not to be resent until a change in operational mode is required. The bits of the control byte continuously determine the type of update performed. Thus, for the first update, DAC7574 requires a start condition, a valid I2C address, a control byte, an MSB byte and an LSB byte. For all consecutive updates, DAC7574 needs an MSB byte and an LSB byte as long as the control command remains the same. Using the I2C high-speed mode (fscl= 3.4 MHz), the clock running at 3.4 MHz, each 12-bit DAC update other than the first update can be done within 18 clock cycles (MSB byte, acknowledge signal, LSB byte, acknowledge signal), at 188.88 KSPS. Using the fast mode (fscl= 400 kHz), clock running at 400 kHz, maximum DAC update rate is limited to 22.22 KSPS. Once a stop condition is received DAC7574 releases the I2C bus and awaits a new start condition. Address Byte MSB 1 0 0 1 1 A1 A0 LSB R/W The address byte is the first byte received following the START condition from the master device. The first five bits (MSBs) of the address are factory preset to 10011. The next two bits of the address are the device select bits A1 and A0. The A1, A0 address inputs can be connected to VDD or digital GND, or can be actively driven by TTL/CMOS logic levels. The device address is set by the state of these pins during the power-up sequence of the DAC7574. Up to 4 devices (DAC7574) can still be connected to the same I2C-Bus. 14 www.ti.com DAC7574 SLAS375 - JUNE 2003 Broadcast Address Byte MSB 1 0 0 1 0 0 0 LSB 0 Broadcast addressing is also supported by DAC7574. Broadcast addressing can be used for synchronously updating or powering down multiple DAC7574 devices. DAC7574 is designed to work with other members of the DAC857x and DAC757x families to support multichannel synchronous update. Using the broadcast address, DAC7574 responds regardless of the states of the address pins. Broadcast is supported only in write mode (Master writes to DAC7574). Control Byte MSB 0 0 L1 L0 X Sel1 Sel0 LSB PD0 Table 1. Control Register Bit Descriptions Bit Name L1 L2 Bit Number/Description Load1 (Mode Select) Bit Load0 (Mode Select) Bit 00 Are used for selecting the update mode. Store I2C data. The contents of MS-BYTE and LS-BYTE (or power down information) are stored in the temporary register of a selected channel. This mode does not change the DAC output of the selected channel. Update selected DAC with I2C data. Most commonly utilized mode. The contents of MS-BYTE and LS-BYTE (or power down information) are stored in the temporary register and in the DAC register of the selected channel. This mode changes the DAC output of the selected channel with the new data. 4-Channel synchronous update. The contents of MS-BYTE and LS-BYTE (or power down information) are stored in the temporary register and in the DAC register of the selected channel. Simultaneously, the other three channels get updated with previously stored data from the temporary register. This mode updates all four channels together. Broadcast update mode. This mode has two functions. In broadcast mode, DAC7574 responds regardless of local address matching, and channel selection becomes irrelevant as all channels update. This mode is intended to enable up to 16 channels simultaneous update, if used with the I2C broadcast address (1001 0000). If Sel1=0 If Sel1=1 All four channels are updated with the contents of their temporary register data. All four channels are updated with the MS-BYTE and LS-BYTE data or powerdown. Channel Select Bits Channel A Channel B Channel C Channel D Normal operation Power-down flag (MSB7 and MSB6 indicate a power-down operation, as shown in Table 2). 01 10 11 Sel1 Sel0 Buff Sel1 Bit Buff Sel0 Bit 00 01 10 11 PD0 Power Down Flag 0 1 15 DAC7574 SLAS375 - JUNE 2003 www.ti.com Table 2. Control Byte C7 0 C6 0 C5 Load1 C4 Load0 C3 Don't Care C2 Ch Sel 1 C1 Ch Sel 0 C0 PD0 MSB7 MSB (PD1) MSB6 MSB-1 (PD2) MSB5... MSB-2 ...LSB DESCRIPTION (Address Select) 0 0 X 0 0 0 Data Write to temporary register A (TRA) with data Write to temporary register B (TRB) with data Write to temporary register C (TRC) with data Write to temporary register D (TRD) with data 0 Write to TRx (selected by C2 &C1 w/Powerdown Command Write to TRx (selected by C2 &C1 and load DACx w/data 0 Power-down DACx (selected by C2 and C1) Write to TRx (selected by C2 &C1 w/ data and load all DACs 0 Power-down DACx (selected by C2 and C1) & load all DACs Update all DACs, all devices with previously stored TRx data Update all DACs, all devices with MSB[7:0] and LSB[7:0] data 0 Power-down all DACs, all devices 0 0 X 0 1 0 Data 0 0 X 1 0 0 Data 0 0 X 1 1 0 Data (00, 01, 10, or 11) 0 0 X (00, 01, 10, or 11) 0 1 X (00, 01, 10, or 11) 0 1 X (00, 01, 10, or 11) 1 0 X (00, 01, 10, or 11) 1 0 X 1 see Table 8 0 Data 1 see Table 8 0 Data 1 see Table 8 Broadcast Modes (controls up to 4 devices on a single serial bus) X X 1 1 X 0 X X X X X X X 1 1 1 1 X X 1 1 X X 0 1 Data see Table 8 Most Significant Byte Most Significant Byte MSB[7:0] consists of eight most significant bits of 12-bit unsigned binary D/A conversion data. C0=1, MSB[7], MSB[6] indicate a powerdown operation as shown in Table 8. Least Significant Byte Least Significant Byte LSB[7:0] consists of the 4 least significant bits of the 12-bit unsigned binary D/A conversion data, followed by 4 don't care bits. DAC7574 updates at the falling edge of the acknowledge signal that follows the LSB[0] bit. Default Readback Condition If the user initiates a readback of a specified channel without first writing data to that specified channel, the default readback is all zeros, since the readback register is initialized to 0 during the power on reset phase. 16 www.ti.com DAC7574 SLAS375 - JUNE 2003 LDAC Functionality Depending on the control byte, DACs are synchronously updated on the falling edge of the acknowledge signal that follows LS byte. The LDAC pin is required only when an external timing signal is used to update all the channels of the DAC asynchronously. LDAC is a positive edge triggered asynchronous input that allows four DAC output voltages to be updated simultaneously with temporary register data. The LDAC trigger should only be used after the buffers temporary registers are properly updated through software. DAC7574 Registers Table 3. DAC7574 Architecture Register Descriptions Register CTRL[7:0] MSB[7:0] LSB[7:0] TRA[13:0], TRB[13:0], TRC[13:0], TRD[13:0] DRA[13:0], DRB[13:0], DRC[13:0], DRD[13:0] Description Stores 8-bit wide control byte sent by the master Stores the 8 most significant bits of unsigned binary data sent by the master. Can also store 2-bit power-down data. Stores the 4 least significant bits of unsigned binary data sent by the master. 14-bit temporary storage registers assigned to each channel. Two MSBs store power-down information, 12 LSBs store data. 14-bit DAC registers for each channel. Two MSBs store power-down information, 12 LSBs store DAC data. An update of this register means a DAC update with data or power-down. DAC7574 as a Slave Receiver - Standard and Fast Mode Figure 35 shows the standard and fast mode master transmitter addressing a DAC7574 Slave Receiver with a 7-bit address. S SLAVE ADDRESS R/W A Ctrl-Byte A MS-Byte A LS-Byte A/A P "0" (write) Data Transferred (n* Words + Acknowledge) Word = 12 Bit DAC7574 I2C-SLAVE ADDRESS: MSB 1 0 0 1 1 A1 A0 LSB R/W `0' = Write to DAC7574 `1' = Read from DAC7574 A0 = I2C Address Pin A1 = I2C Address Pin From Master to DAC7574 From DAC7574 to Master A= A= S= Sr = P= Acknowledge (SDA LOW) Not Acknowledge (SDA HIGH) START Condition Repeated START Condition STOP Condition Factory Preset Figure 35. Standard and Fast Mode: Slave Receiver 17 DAC7574 SLAS375 - JUNE 2003 www.ti.com DAC7574 as a Slave Receiver - High-Speed Mode Figure 36 shows the high-speed mode master transmitter addressing a DAC7574 Slave Receiver with a 7-bit address. F/S-Mode S HS-Master Code A Sr Slave Address HS-Mode R/W A Ctrl-Byte A MS-Byte A LS-Byte A/A P F/S-Mode "0" (write) HS-Mode Master Code: MSB 0 0 0 0 1 X X LSB R/X Control Byte: MSB 0 MS-Byte: MSB D11 D10 D9 D8 D7 D6 D5 LSB D4 L1 L0 Sel1 Sel0 PD0 X = = = = = 0 Data Transferred (n* Words + Acknowledge) Word = 12 Bit HS-Mode Continues Sr Slave Address LSB L1 L0 X Sel1 Sel2 PD0 LS-Byte: MSB D3 D2 D1 D0 X X X LSB X Load1 (Mode Select) Bit Load0 (Mode Select) Bit Buff Sel1 (Channel) Select Bit Buff Sel0 (Channel) Select Bit Power Down Flag = Don't Care D11 - D0 = Data Bits Figure 36. High-Speed Mode: Slave Receiver 18 www.ti.com DAC7574 SLAS375 - JUNE 2003 Master Transmitter Writing to a Slave Receiver (DAC7574) in Standard/Fast Modes All write access sequences begin with the device address (with R/W = 0) followed by the control byte. This control byte specifies the operation mode of DAC7574 and determines which channel of DAC7574 is being accessed in the subsequent read/write operation. The LSB of the control byte (PD0-Bit) determines if the following data is power-down data or regular data. With (PD0-Bit = 0) the DAC7574 expects to receive data in the following sequence HIGH-BYTE -LOW-BYTE - HIGH-BYTE - LOW-BYTE..., until a STOP Condition or REPEATED START Condition on the I2C-Bus is recognized (refer to the DATA INPUT MODE section of Table 4). With (PD0-Bit = 1) the DAC7574 expects to receive 2 Bytes of power-down data (refer to the POWER DOWN MODE section of Table 4). Table 4. Write Sequence in F/S Mode DATA INPUT MODE Transmitter Master Master DAC7574 Master DAC7574 Master DAC7574 Master DAC7574 Master POWER DOWN MODE Transmitter Master Master DAC7574 Master DAC7574 Master DAC7574 Master DAC7574 Master (1) (2) 0 0 0 PD1 PD2 0 0 0 Load 1 1 0 0 1 Load 0 0 0 MSB 6 5 4 3 Start 1 x 0 x A1 Buff Sel 1 0 x A0 Buff Sel 0 0 x R/W PD0 0 x DAC7574 Acknowledges Control byte (PD0 = 1) Writing data word, high byte Writing data word, low byte Done DAC7574 Acknowledges DAC7574 Acknowledges DAC7574 Acknowledges Stop or Repeated Start (1) 2 1 LSB Comment Begin sequence Write addressing (R/W=0) D3 D2 D1 D11 D10 D9 0 0 Load 1 1 0 0 1 Load 0 D8 D0 MSB 6 5 4 3 Start 1 x D7 x A1 Buff Sel 1 D6 x A0 Buff Sel 0 D5 x R/W PD0 D4 x DAC7574 Acknowledges Control byte (PD0=0) Writing data word, high byte Writing data word, low byte Data or done (2) DAC7574 Acknowledges DAC7574 Acknowledges DAC7574 Acknowledges Data or Stop or Repeated Start (1) 2 1 LSB Comment Begin sequence Write addressing (R/W=0) Use repeated START to secure bus operation and loop back to the stage of write addressing for next Write. Once DAC7574 is properly addressed and control byte is sent, HIGH-BYTE-LOW-BYTE sequences can repeat until a STOP condition or repeated START condition is received. 19 DAC7574 SLAS375 - JUNE 2003 www.ti.com Master Transmitter Writing to a Slave Receiver (DAC7574) in HS Mode When writing data to the DAC7574 in HS-mode, the master begins to transmit what is called the HS-Master Code (0000 1XXX) in F/S-mode. No device is allowed to acknowledge the HS-Master Code, so the HS-Master Code is followed by a NOT acknowledge. The master then switches to HS-mode and issues a repeated start condition, followed by the address byte (with R/W = 0) after which the DAC7574 acknowledges by pulling SDA low. This address byte is usually followed by the control byte, which is also acknowledged by the DAC7574. The LSB of the control byte (PD0-Bit) determines if the following data is power-down data or regular data. With (PD0-Bit = 0) the DAC7574 expects to receive data in the following sequence HIGH-BYTE - LOW-BYTE - HIGH-BYTE - LOW-BYTE...., until a STOP condition or repeated start condition on the I2C-Bus is recognized (refer to Table 5 HS-MODE WRITE SEQUENCE - DATA). With (PD0-Bit = 1) the DAC7574 expects to receive 2 bytes of power-down data (refer to Table 5 HS-MODE WRITE SEQUENCE - POWER DOWN). Table 5. Master Transmitter Writes to Slave Receiver (DAC7574) in HS-Mode HS MODE WRITE SEQUENCE - DATA Transmitter Master Master NONE Master Master DAC7574 Master DAC7574 Master DAC7574 Master DAC7574 Master Transmitter Master Master NONE Master Master DAC7574 Master DAC7574 Master DAC7574 Master DAC7574 Master (1) (2) 0 0 0 PD1 PD2 0 0 0 Load 1 1 0 0 0 0 0 0 MSB 6 5 D3 D2 D1 D11 D10 D9 0 0 Load 1 1 0 0 0 0 0 0 MSB 6 5 4 3 Start 1 X X X 2 1 LSB Comment Begin sequence HS Mode Master Code No device may acknowledge HS master code A1 Buff Sel 1 D6 x A0 Buff Sel 0 D5 x R/W PD0 D4 x Write addressing (R/W=0) Control byte (PD0=0) Writing data word, MSB Writing data word, LSB Data or done (2) 1 X LSB X Comment Begin sequence X HS Mode Master Code No device may acknowledge HS master code A1 Buff Sel 1 0 x A0 Buff Sel 0 0 x R/W PD0 0 x Write addressing (R/W = 0) Control Byte (PD0=1) Writing data word, high byte Writing data word, low byte Done Not Acknowledge Repeated Start 1 Load 0 D8 D0 1 0 D7 x DAC7574 Acknowledges DAC7574 Acknowledges DAC7574 Acknowledges DAC7574 Acknowledges Data or Stop or Repeated Start (1) 4 3 Start 1 2 HS MODE WRITE SEQUENCE - POWER DOWN Not Acknowledge Repeated Start 1 Load 2 0 0 1 0 0 x DAC7574 Acknowledges DAC7574 Acknowledges DAC7574 Acknowledges DAC7574 Acknowledges Stop or repeated start (1) Use repeated start to secure bus operation and loop back to the stage of write addressing for next Write. Once DAC7574 is properly addressed and control byte is sent, high-byte-low-byte sequences can repeat until a stop or repeated start condition is received. 20 www.ti.com DAC7574 SLAS375 - JUNE 2003 DAC7574 as a Slave Transmitter - Standard and Fast Mode Figure 37 shows the standard and fast mode master transmitter addressing a DAC7574 Slave Transmitter with a 7-bit address. (DAC7574) (DAC7574) (DAC7574) (MASTER) (MASTER) S SLAVE ADDRESS R/W A Ctrl <7:1> PD0 A Sr Slave Address '0' (write) '0' = (Normal Mode) R/W A MS-Byte A LS-Byte A P '1' (read) Data Transferred (2 Bytes + Acknowledge) (MASTER) (MASTER) (MASTER) (DAC7574) PD0 A Sr Slave Address '1' = (Power Down Flag) PDN-Byte: MSB PD1 PD2 1 1 1 1 1 LSB 1 R/W A PDN-Byte A MS-Byte A LS-Byte A P '1' (read) Data Transferred (3 Bytes + Acknowledge) PD1 = Power-Down Bit PD2 = Power-Down Bit Figure 37. Standard and Fast Mode: Slave Transmitter DAC7574 as a Slave Transmitter - High-Speed Mode Figure 38 shows an I2C-Master addressing DAC7574 in high-speed mode (with a 7-bit address), as a Slave Transmitter. F/S-Mode S HS-Master Code A HS-Mode (DAC7574) Sr Slave Address (DAC7574) Sr Slave Address (DAC7574) (MASTER) (MASTER) R/W A Ctrl <7:1> PD0 A '0' (write) '0' = (Normal Mode) R/W A MS-Byte A LS-Byte A P '1' (read) Data Transferred (2 Bytes + Acknowledge) (MASTER) (MASTER) (MASTER) (DAC7574) PD0 A Sr Slave Address '1' = (Power -Down Flag) R/W A PDN-Byte A '1' (read) MS-Byte A LS-Byte A P Data Transferred (3 Bytes + Acknowledge) Figure 38. High-Speed Mode: Slave Transmitter 21 DAC7574 SLAS375 - JUNE 2003 www.ti.com Master Receiver Reading From a Slave Transmitter (DAC7574) in Standard/Fast Modes When reading data back from the DAC7574, the user begins with an address byte (with R/W = 0) after which the DAC7574 will acknowledge by pulling SDA low. This address byte is usually followed by the Control Byte, which is also acknowledged by the DAC7574. Following this there is a REPEATED START condition by the Master and the address is resent with (R/W = 1). This is acknowledged by the DAC7574, indicating that it is prepared to transmit data. Two or three bytes of data are then read back from the DAC7574, depending on the (PD0-Bit). The value of Buff-Sel1 and Buff-Sel0 determines, which channel data is read back. A STOP Condition follows. With the (PD0-Bit = 0) the DAC7574 transmits 2 bytes of data, HIGH-BYTE followed by the LOW-BYTE (refer to Table 2. Data Readback Mode - 2 bytes). With the (PD0-Bit = 1) the DAC7574 transmits 3 bytes of data, POWER-DOWN-BYTE followed by the HIGH-BYTE followed by the LOW-BYTE (refer to Table 2. Data Readback Mode - 3 bytes). Table 6. Read Sequence in F/S Mode DATA READBACK MODE - 2 BYTES Transmitter Master Master DAC7574 Master DAC7574 Master Master DAC7574 DAC7574 Master DAC7574 Master Master DATA READBACK MODE - 3 BYTES Transmitter Master Master DAC7574 Master DAC7574 Master Master DAC7574 DAC7574 Master DAC7574 Master DAC7574 Master Master D3 D2 D1 D11 D10 D9 PD1 PD2 1 1 0 0 1 1 D8 D0 0 0 Load 1 1 0 0 1 Load 0 MSB 6 5 4 3 Start 1 x A1 Buff Sel 1 A0 Buff Sel 0 R/W PD0 DAC7574 Acknowledges Control byte (PD0=1) DAC7574 Acknowledges Repeated Start 1 1 D7 x A1 1 D6 x A0 1 D5 x R/W 1 D4 x Read addressing (R/W = 1) Read power down byte Reading data word, high byte Reading data word, low byte Master signal end of read Done DAC7574 Acknowledges Master Acknowledges Master Acknowledges Master Not Acknowledges Stop or Repeated Start (1) 2 1 LSB Comment Begin sequence Write addressing (R/W=0) D3 D2 D1 D11 D10 D9 1 0 0 1 D8 D0 0 0 Load 1 1 0 0 1 Load 0 MSB 6 5 4 3 Start 1 x A1 Buff Sel 1 A0 Buff Sel 0 R/W PD0 DAC7574 Acknowledges Control byte (PD0=0) DAC7574 Acknowledges Repeated Start 1 D7 x A1 D6 x A0 D5 x R/W D4 x Read addressing (R/W = 1) Reading data word, high byte Reading data word, low byte Master signal end of read Done DAC7574 Acknowledges Master Acknowledges Master Not Acknowledges Stop or Repeated Start (1) 2 1 LSB Comment Begin sequence Write addressing (R/W=0) (1) 22 Use repeated start to secure bus operation and loop back to the stage of write addressing for next Write. www.ti.com DAC7574 SLAS375 - JUNE 2003 Master Receiver Reading From a Slave Transmitter (DAC7574) in HS-Mode When reading data to the DAC7574 in HS-MODE, the master begins to transmit, what is called the HS-Master Code (0000 1XXX) in F/S-mode. No device is allowed to acknowledge the HS-Master Code, so the HS-Master Code is followed by a NOT acknowledge. The Master then switches to HS-mode and issues a REPEATED START condition, followed by the address byte (with R/W = 0) after which the DAC7574 acknowledges by pulling SDA low. This address byte is usually followed by the control byte, which is also acknowledged by the DAC7574. Then there is a REPEATED START condition initiated by the master and the address is resent with (R/W = 1). This is acknowledged by the DAC7574, indicating that it is prepared to transmit data. Two or Three bytes of data are then read back from the DAC7574, depending on the (PD0-Bit). The value of Buff-Sel1 and Buff-Sel0 determines, which channel data is read back. A STOP condition follows. With the (PD0-Bit = 0) the DAC7574 transmits 2 bytes of data, HIGH-BYTE followed by LOW-BYTE (refer to Table 7 HS-Mode Readback Sequence). With the (PD0-Bit = 1) the DAC7574 transmits 3 bytes of data, POWER-DOWN-BYTE followed by the HIGH-BYTE followed by the LOW-BYTE (refer to Table 7 HS-Mode Readback Sequence). Table 7. Master Receiver Reading Slave Transmitter (DAC7574) in HS-Mode HS MODE READBACK SEQUENCE Transmitter Master Master NONE Master Master DAC7574 Master DAC7574 Master Master DAC7574 DAC7574 Master DAC7574 Master DAC7574 Master Master D3 D2 D1 D11 D10 D9 PD1 PD2 1 1 0 0 1 1 D8 D0 0 0 Load 1 1 0 0 1 Load 0 0 0 0 0 MSB 6 5 4 3 Start 1 Not Acknowledge Repeated Start 1 X A1 Buff Sel 1 A0 Buff Sel 0 R/W PD0 Write addressing (R/W=0) Control byte (PD0 = 1) DAC7574 Acknowledges DAC7574 Acknowledges Repeated Start 1 1 D7 x A1 1 D6 x A0 1 D5 x R/W 1 D4 x Read addressing (R/W=1) Power-down byte Reading data word, high byte Reading data word, low byte Master signal end of read Done DAC7574 Acknowledges Master Acknowledges Master Acknowledges Master Not Acknowledges Stop or Repeated Start X X X 2 1 LSB Comment Begin sequence HS Mode Master Code No device may acknowledge HS master code Power-On Reset The DAC7574 contains a power-on-reset circuit that controls the output voltage during power up. On power up, the DAC register is filled with zeros and the output voltage is 0 V; it remains there until a valid write sequence is made to the DAC. This is useful in applications where it is important to know the state of the output of the DAC while it is in the process of powering up. No device pin should be brought high before supply is applied. 23 DAC7574 SLAS375 - JUNE 2003 www.ti.com Power-Down Modes The DAC7574 contains four separate power-down modes of operation. The modes are programmable via two most significant bits of the MSB byte, while (CTRL[0] = PD0 = 1). Table 8 shows how the state of these bits correspond to the mode of operation of the device. Table 8. Power-Down Modes of Operation for the DAC7574 CTRL[0] 1 1 1 1 MSB[7] 0 0 1 1 MSB[6] 0 1 0 1 OPERATING MODE High Impedance Output 1 k to GND 100 k to GND High Impedance When (CTRL[0] = PD0 = 0), the device works normally with its normal power consumption of 150 A at 5 V per channel. However, for the three power-down modes, the supply current falls to 200 nA at 5 V (50 nA at 3 V). Not only does the supply current fall but also the output stage is also internally switched from the output of the amplifier to a resistor network of known values. This has the advantage that the output impedance of the device is known while in power-down mode. There are three different options: The output is connected internally to GND through a 1 k resistor, a 100 k resistor or left open-circuit (high impedance). The output stage is illustrated in Figure 39. Amplifier Resistor String DAC VOUT Powerdown Circuitry Resistor Network Figure 39. Output Stage During Power Down All linear circuitry is shut down when the power-down mode is activated. However, the contents of the DAC register are unaffected when in power-down. The time to exit power down is typically 2.5 s for VDD = 5 V and 5 s for VDD = 3 V. (See the Typical Curves section for additional information.) The DAC7574 offers a flexible power-down interface based on channel register operation. A channel consists of a single 12 bit DAC with power-down circuitry, a temporary storage register (TR) and a DAC register (DR). TR and DR are both 14 bits wide. Two MSBs represent the power-down condition and the 12 LSBs represent data for TR and DR. By using bits 13 and 14 of TR and DR, a power-down condition can be temporarily stored and used just like data. Internal circuits ensure that MSB[7] and MSB[6] get transferred to TR[13] and TR[12] (DR[13] and DR[12]) when the power-down flag (CTRL[0] = PD0) is set. Therefore, DAC7574 treats power-down conditions like data and all the operational modes are still valid for power down. It is possible to broadcast a power-down condition to all the DAC7574s in the system, or it is possible to simultaneously power down a channel while updating data on other channels. CURRENT CONSUMPTION The DAC7574 typically consumes 150A at VDD = 5 V and 125A at VDD = 3 V for each active channel, including reference current consumption. Additional current consumption can occur at the digital inputs if VIH << VDD. For most efficient power operation, CMOS logic levels are recommended at the digital inputs to the DAC. In power-down mode, typical current consumption is 200 nA. A delay time of 10 to 20 ms after a power-down command is issued to the DAC is typically sufficient for the power-down current to drop below 10 A. 24 www.ti.com DAC7574 SLAS375 - JUNE 2003 DRIVING RESISTIVE AND CAPACITIVE LOADS The DAC7574 output stage is capable of driving loads of up to 1000 pF while remaining stable. Within the offset and gain error margins, the DAC7574 can operate rail-to-rail when driving a capacitive load. Resistive loads of 2 k can be driven by the DAC7574 while achieving a typical load regulation of 1%. As the load resistance drops below 2 k, the load regulation error increases. When the outputs of the DAC are driven to the positive rail under resistive loading, the PMOS transistor of each Class-AB output stage can enter into the linear region. When this occurs, the added IR voltage drop deteriorates the linearity performance of the DAC. This only occurs within approximately the top 20 mV of the DAC's digital input-to-voltage output transfer characteristic. The reference voltage applied to the DAC7574 may be reduced below the supply voltage applied to VDD in order to eliminate this condition if good linearity is a requirement at full scale (under resistive loading conditions). CROSSTALK The DAC7574 architecture uses separate resistor strings for each DAC channel in order to achieve ultra-low crosstalk performance. DC crosstalk seen at one channel during a full-scale change on the neighboring channel is typically less than 0.5 LSBs. The ac crosstalk measured (for a full-scale, 1 kHz sine wave output generated at one channel, and measured at the remaining output channel) is typically under -100 dB. OUTPUT VOLTAGE STABILITY The DAC7574 exhibits excellent temperature stability of 3 ppm/C typical output voltage drift over the specified temperature range of the device. This enables the output voltage of each channel to stay within a 25 V window for a 1C ambient temperature change. Combined with good dc noise performance and true 12-bit differential linearity, the DAC7574 becomes a perfect choice for closed-loop control applications. SETTLING TIME AND OUTPUT GLITCH PERFORMANCE Settling time to within the 12-bit accurate range of the DAC7574 is achievable within 10 s for a full-scale code change at the input. Worst case settling times between consecutive code changes is typically less than 2 s. The high-speed serial interface of the DAC7574 is designed in order to support up to 188ksps update rate. For full-scale output swings, the output stage of each DAC7574 channel typically exhibits less than 100 mV of overshoot and undershoot when driving a 200 pF capacitive load. Code-to-code change glitches are extremely low (~10 V) given that the code-to-code transition does not cross an Nx256 code boundary. Due to internal segmentation of the DAC7574, code-to-code glitches occur at each crossing of an Nx256 code boundary. These glitches can approach 100 mVs for N = 15, but settle out within ~2 s. Sufficient bypass capacitance is required to ensure 10 s settling under capacitive loading. To observe the settling performance under resistive load conditions, the power supply (hence DAC7574 reference supply) must settle quicker than the DAC7574. 25 DAC7574 SLAS375 - JUNE 2003 www.ti.com APPLICATION INFORMATION The following sections give example circuits and tips for using the DAC7574 in various applications. For more information, contact your local TI representative, or visit the Texas Instruments website at http://www.ti.com. BASIC CONNNECTIONS For many applications, connecting the DAC7574 is extremely simple. A basic connection diagram for the DAC7574 is shown in Figure 40. The 0.1 F bypass capacitors help provide the momentary bursts of extra current needed from the supplies. DAC7574 1 VOUTA 2 VOUTB 3 GND A1 10 A0 9 VDD 8 SDA 7 SCL 6 I2C Pullup Resistors 1 k to 10 k (typical) VDD 4 VOUTC 5 VOUTD Microcontroller or Microprocessor With I2C Port SCL SDA NOTE: DAC7574 power and input/output connections are omitted for clarity, except I2C Inputs. Figure 40. Typical DAC7574 Connections The DAC7574 interfaces directly to standard mode, fast mode and high-speed mode I2C controllers. Any microcontroller's I2C peripheral, including master-only and non-multiple-master I2C peripherals, work with the DAC7574. The DAC7574 does not perform clock-stretching (i.e., it never pulls the clock line low), so it is not necessary to provide for this unless other devices are on the same I2C bus. Pullup resistors are necessary on both the SDA and SCL lines because I2C bus drivers are open-drain. The size of the these resistors depend on the bus operating speed and capacitance on the bus lines. Higher-value resistors consume less power, but increase the transition times on the bus, limiting the bus speed. Lower-value resistors allow higher speed at the expense of higher power consumption. Long bus lines have higher capacitance and require smaller pullup resistors to compensate. If the pullup resistors are too small the bus drivers may not be able to pull the bus line low. USING GPIO PORTS FOR I2C Most microcontrollers have programmable input/output pins that can be set in software to act as inputs or outputs. If an I2C controller is not available, the DAC7574 can be connected to GPIO pins, and the I2C bus protocol simulated, or bit-banged, in software. An example of this for a single DAC7574 is shown in Figure 41. 26 www.ti.com DAC7574 SLAS375 - JUNE 2003 APPLICATION INFORMATION (continued) DAC7574 1 VOUTA 2 VOUTB 3 GND A1 10 A0 VDD 9 8 VDD 4 VOUTC 5 VOUTD SDA 7 SCL 6 Microcontroller or Microprocessor GPIO-1 GPIO-2 NOTE: DAC7574 power and input/output connections are omitted for clarity, except I2C Inputs. Figure 41. Using GPIO With a Single DAC7574 Bit-banging I2C with GPIO pins can be done by setting the GPIO line to zero and toggling it between input and output modes to apply the proper bus states. To drive the line low, the pin is set to output a zero; to let the line go high, the pin is set to input. When the pin is set to input, the state of the pin can be read; if another device is pulling the line low, this reads as a zero in the port's input register. Note that no pullup resistor is shown on the SCL line. In this simple case the resistor is not needed. The microcontroller can simply leave the line on output, and set it to one or zero as appropriate. It can do this because the DAC7574 never drives its clock line low. This technique can also be used with multiple devices, and has the advantage of lower current consumption due to the absence of a resistive pullup. If there are any devices on the bus that may drive their clock lines low, the above method should not be used. The SCL line should be high-Z or zero, and a pullup resistor provided as usual. Note also that this cannot be done on the SDA line in any case, because the DAC7574 drives the SDA line low from time to time, as all I2C devices do. Some microcontrollers have selectable strong pullup circuits built in to their GPIO ports. In some cases, these can be switched on and used in place of an external pullup resistor. Weak pullups are also provided on some microcontrollers, but usually these are too weak for I2C communication. Test any circuit before committing it to production. 27 DAC7574 SLAS375 - JUNE 2003 www.ti.com APPLICATION INFORMATION (continued) POWER SUPPLY REJECTION The positive reference voltage input of DAC7574 is internally tied to the power supply pin of the device. This increases I2C system flexibility, creating room for an extra I2C address pin in a low pin-count package. To eliminate the supply noise appearing at the DAC output, the user must pay close attention to how DAC7574 is powered. The supply to DAC7574 must be clean and well regulated. For best performance, use of a precision voltage reference is recommended to supply power to DAC7574. This is equivalent to providing a precision external reference to the device. Due to low power consumption of DAC7574, load regulation errors are negligible. In order to avoid excess power consumption at the Schmitt-triggered inputs of DAC7574, the precision reference voltage should be close to the I2C bus pullup voltage. For 3-V, 3.3-V and 5-V I2C bus pullup voltages, REF2930, REF2933 and REF02 precision voltage references are recommended respectively. These precision voltage references can be used to supply power for multiple devices on a system. USING REF02 AS A POWER SUPPLY FOR DAC7574 Due to the extremely low supply current required by the DAC7574, a possible configuration is to use a REF02 +5 V precision voltage reference to supply the required voltage to the DAC7574's supply input as well as the reference input, as shown in Figure 42. This is especially useful if the power supply is quite noisy or if the system supply voltages are at some value other than 5 V. The REF02 outputs a steady supply voltage for the DAC7574. If the REF02 is used, the current it needs to supply to the DAC7574 is 600 A typical and 900 A max for VDD = 5 V. When a DAC output is loaded, the REF02 also needs to supply the current to the load. The total typical current required (with a 5-k load on a single DAC output) is: 600 A + (5 V / 5 k) = 1.6 mA The load regulation of the REF02 is typically 0.005%/mA, which results in an error of 400V for 1.6-mA of current drawn from it. This corresponds to a 0.33 LSB error for a 0 V to 5 V output range. 15 V REF02 5V 1.6 mA I2C Interface SCL SDA VDD DAC7574 VOUT = 0 V to 5 V Figure 42. REF02 Power Supply LAYOUT A precision analog component requires careful layout, adequate bypassing, and clean, well-regulated power supplies. The power applied to VDD should be well-regulated and low noise. Switching power supplies and dc/dc converters often have high-frequency glitches or spikes riding on the output voltage. In addition, digital components can create similar high-frequency spikes as their internal logic switches states. This noise can easily couple into the DAC output voltage through various paths between the power connections and analog output. 28 www.ti.com DAC7574 SLAS375 - JUNE 2003 As with the GND connection, VDD should be connected to a positive power-supply plane or trace that is separate from the connection for digital logic until they are connected at the power-entry point. In addition, a 1 F to 10 F capacitor in parallel with a 0.1 F bypass capacitor is strongly recommended. In some situations, additional bypassing may be required, such as a 100 F electrolytic capacitor or even a Pi filter made up of inductors and capacitors--all designed to essentially low-pass filter the -5 V supply, removing the high-frequency noise. 29 MECHANICAL DATA MPDS035A - JANUARY 1998 - REVISED SEPTEMBER 2001 DGS (S-PDSO-G10) 0,27 0,17 10 6 PLASTIC SMALL-OUTLINE PACKAGE 0,50 0,08 M 0,15 NOM 3,05 2,95 4,98 4,78 Gage Plane 0,25 1 3,05 2,95 5 0- 6 0,69 0,41 Seating Plane 1,07 MAX 0,15 0,05 0,10 4073272/B 08/01 NOTES: A. B. C. D. All linear dimensions are in millimeters. This drawing is subject to change without notice. Body dimensions do not include mold flash or protrusion. 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