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| PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter Features * * * * VIN Range: 2.7V to 5.5V VOUT: 1.5V and 1.34V 300mA Maximum Output Current Ultra-Small Solution for Portable Applications Small Footprint Only Three External Ceramic Capacitors Required No Inductor High Efficiency over the Output Current Range Excellent Transient Performance 35A Typical Quiescent Current <1.0A Shutdown Current Up to 2MHz Switching Frequency Integrated Soft-Start Short-Circuit and Thermal Protection 2.0x2.1mm SC70JW-8 Package -40C to 85C Temperature Range General Description The AAT3183 is a high efficiency step-down charge pump converter providing up to 300mA of output current. The 1/2x (gain) charge pump converter topology provides enhanced efficiency over conventional LDO regulators and requires only three low cost ceramic capacitors. No inductor is required; saving space and cost when compared to inductive switching regulators. The AAT3183 typically consumes 35A of no load (zero output current) quiescent current, making it ideal for portable battery powered systems. Shutdown current is less than 1A. The AAT3183 soft-start prevents excessive inrush current while providing monotonic turn-on characteristics. The device includes integrated short-circuit and overtemperature (thermal) protection to safeguard system components. The AAT3183 is available in a Pb-free 2.0x2.1mm SC70JW-8 package. Operating temperature range is -40C to +85C. * * * * * * * * * Applications * * * * * Camcorders Digital Still Cameras DSP Core Supplies PDAs, Handheld Devices, Notebook PCs Smart Phones Typical Application CFLY 1F C1VIN CIN 1F IN C1+ OUT VOUT AAT3183 COUT 4.7F VENABLE EN GND 3183.2008.02.1.3 www.analogictech.com 1 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter Pin Descriptions Pin # 1 2 3 4 5 6, 7, 8 Symbol OUT C1+ C1IN EN GND Function Charge pump converter output. Requires a ceramic capacitor to ground. Flying capacitor positive terminal. Connect flying capacitor between C1+ and C1-. Flying capacitor negative terminal. Connect flying capacitor between C1+ and C1-. Charge pump converter input. Requires a ceramic capacitor to ground. Enable pin. Active high. Ground. Pin Configuration SC70JW-8 (Top View) OUT C1+ C1IN 1 8 GND GND GND EN 2 3 4 7 6 5 2 www.analogictech.com 3183.2008.02.1.3 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter Absolute Maximum Ratings1 Symbol VIN VEN TJ TS TLEAD Description Input Voltage to Ground Enable Voltage to Ground Operating Junction Temperature Range2 Storage Temperature Range Maximum Soldering Temperature (at leads, 10 sec) Value -0.3 to 6.0 -0.3 to 6.0 -40 to 150 -65 to 150 300 Units V V C C C Thermal Information Symbol JA PD Description Thermal Resistance3 Maximum Power Dissipation at TA = 25C Value 160 625 Units C/W mW 1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time. 2. TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: TJ = TA + PD * JA. 3. Mounted on an FR4 board. 3183.2008.02.1.3 www.analogictech.com 3 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter Electrical Characteristics1 VIN = 3.6V, CIN = CFLY = 1.0F, COUT = 4.7F, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = 25C. Symbol VIN VOUT VUVLO IOUT IQ Description Input Voltage Output Voltage Accuracy Under-Voltage Lockout (UVLO) Output Current Quiescent Current Shutdown Current Output Voltage Ripple Line Regulation Load Regulation Soft-Start Time Clock Frequency Enable Threshold Low Enable Threshold High EN Input Leakage Output Impedance Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis Conditions No Load, TA = 25C No Load VIN Rising Hysteresis VIN Falling VEN = VIN, No Load VEN = GND IOUT = 300mA IOUT = 150mA IOUT = 100mA IOUT = 10mA 3.2V VIN 5.5V, IOUT = 50mA 0mA IOUT 150mA IOUT = 300mA Min 2.7 -1 -2 Typ Max 5.5 +1 +2 2 Units V % V 1.5 0.15 1.3 35 12 16 17 17 2.9 0.053 100 2 300 60 1 mA A VPP VOUT/VIN VOUT/IOUT TSS FCLK VEN(L) VEN(H) IEN ROUT TSD THYS mV mV/V mV/mA s MHz V V A C C 0.4 1.4 1 1 150 15 1. The AAT3183 is guaranteed to meet performance specifications over the -40C to +85C operating temperature range and is assured by design, characterization, and correlation with statistical process controls. 4 www.analogictech.com 3183.2008.02.1.3 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter Typical Characteristics Efficiency vs. Output Current (VOUT = 1.5V) 90 80 Efficiency vs. Output Current (VOUT = 1.34V) 90 80 70 60 50 40 30 20 10 0 0.1 VIN = 3.6V Efficiency (%) VIN = 4.2V Efficiency (%) 70 60 50 40 30 20 10 0 0.1 VIN = 5.5V VIN = 5.0V VIN = 3.3V VIN = 3.6V VIN = 4.2V VIN = 5.0V VIN = 5.5V 1 10 100 1000 1 10 100 1000 Output Current (mA) Output Current (mA) Output Voltage Error vs. Output Current (VOUT = 1.5V) Output Voltage Error (mV) VIN = 5.0V VIN = 4.2V VIN = 3.6V Output Voltage Error (%) 20 10 0 -10 -20 -30 -40 -50 0.1 Output Voltage Error vs. Output Current (VOUT = 1.34V) 1.5 1 0.5 0 -0.5 -1 -1.5 -2 -2.5 -3 0.1 VIN = 5.5V VIN = 5.5V VIN = 5.0V VIN = 4.2V VIN = 3.6V VIN = 3.3V 1 10 100 1000 1 10 100 1000 Output Current (mA) Output Current (mA) Output Error vs. Input Voltage (VOUT = 1.5V) 2 0 -2 -4 -6 -8 -10 2.7 Output Error vs. Input Voltage (VOUT = 1.34V) 2 0 -2 -4 -6 -8 -10 .001mA 10mA Output Error (%) Output Error (%) 50mA 150mA IOUT = 0.001mA IOUT = 10mA IOUT = 50mA IOUT = 150mA 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) Input Voltage (V) 3183.2008.02.1.3 www.analogictech.com 5 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter Typical Characteristics Output Voltage Error vs. Temperature (VIN = 3.6V; VOUT = 1.5V; IOUT = 150mA) Output Voltage Error (mV) 8.0 6.0 100 90 80 Efficiency vs. Input Voltage (VOUT = 1.5V) 50mA 300mA Efficiency (%) -40 -25 -10 5 20 35 50 65 80 95 4.0 2.0 0.0 -2.0 -4.0 -6.0 -8.0 70 60 50 40 30 20 10 0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Temperature (C) Input Voltage (V) No Load Quiescent Current vs. Input Voltage (VOUT = 1.5V) 100 Output Voltage Ripple vs. Input Voltage (CIN/CFLY = 1F; COUT = 4.7F; IOUT = 300mA) Output Voltage Ripple (mVpp) 100 90 80 70 60 50 40 30 20 10 0 3 3.6 4.2 4.8 5.4 6 Supply Current (A) 90 80 70 60 50 40 30 20 10 0 3.1 3.5 No Post Filter 25C 85C 100pF Post Filter -40C 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) Input Voltage (V) Output Impedance vs. Input Voltage 1.8 1.54 Load Transient Response (VIN = 3.6V; VOUT = 1.5V; IOUT = 5mA to 150mA) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -0.1 Output Current (bottom) (A) Output Impedance () 25C 1.5 Output Voltage (top) (V) 3.5 3.7 3.9 4.1 1.52 1.5 1.48 1.46 1.44 1.42 1.4 1.38 85C 1.2 0.9 -40C 2.9 3.1 3.3 0.6 2.7 Input Voltage (V) Time (50s/div) 6 www.analogictech.com 3183.2008.02.1.3 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter Typical Characteristics Line Transient (VIN = 3.6V to 4.2V) 1.51 6.9 6.4 5.9 5.4 4.9 4.4 3.9 3.4 2.9 1.54 1.53 Output Ripple (VIN = 3.6V; VOUT = 1.5V; IOUT = 300mA) Input Voltage (bottom) (V) Output Voltage (top) (V) 1.505 1.5 1.495 1.49 1.485 1.48 1.475 1.47 Output Ripple (V) 1.52 1.51 1.5 1.49 1.48 1.47 1.46 Time (500s/div) Time (500ns/div) Output Ripple (VIN = 3.6V; VOUT = 1.5V; IOUT = 150mA) 1.54 2 Soft Start (VIN = 3.6V; IOUT = 150mA) 3.5 3 2.5 2 1.5 1 0.5 0 -0.5 Output Voltage (bottom) (V) Enable Voltage (top) (V) Time (500ns/div) 1.53 1.5 1 0.5 0 -0.5 -1 -1.5 -2 Output Ripple (V) 1.52 1.51 1.5 1.49 1.48 1.47 1.46 Time (50s/div) Short Circuit (VIN = 3.6V; VOUT = 1.5V) 2.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 -0.50 Load Current (bottom) (A) Output Voltage (top) (V) 1.50 1.00 0.50 0.00 -0.50 -1.00 -1.50 -2.00 Time (100s/div) 3183.2008.02.1.3 www.analogictech.com 7 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter Functional Block Diagram IN Thermal Protection, Current Limit C1+ Oscillator, Soft Start Charge Transfer EN C1- OUT VREF GND Functional Description The AAT3183 is a 1/2x (gain) charge pump converter providing an output voltage which is less than the input voltage. The step-down (buck) charge pump converter provides a regulated output voltage for input voltages greater than 2x the output voltage plus the required input voltage headroom (see the Applications Information section for more details). The output current range is 0mA (no load) to 300mA. The AAT3183 provides an ultra-small DC-DC solution achieving improved efficiency over LDO step-down regulators. The high switching frequency allows the use of small external capacitors. Only three ceramic capacitors are required to achieve a complete step-down converter solution. Output regulation is maintained with a pulse frequency modulation (PFM) control scheme. PFM compensates for input voltage and output current variations by modulating the frequency of charge pump switching intervals. Switching frequency increases with high output currents (heavy loads) and decreases with low output currents (light loads); with a maximum switching frequency of 2MHz. PFM control provides decreased switching losses and increased efficiency with light loads. This extends battery life under lightly loaded operating conditions. The AAT3183 responds quickly to changes in line voltage and/or output current, providing stable operation with excellent line and load transient behavior. No load (zero output current) quiescent current is 35A (typical). When disabled, the device consumes less than 1A of current (shutdown). 8 www.analogictech.com 3183.2008.02.1.3 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter the voltage at the input to the error amplifier decreases. The error signal increases the effective switching frequency; providing increased current to the output current thus maintaining the desired output voltage. At light loads, the effective switching frequency is greatly reduced which maintains output regulation while minimizing switching losses. Operating efficiency () is defined as the output power divided by the input power. Integrated soft-start limits inrush current, maintains monotonic turn-on characteristics and eliminates output voltage overshoot. The device includes short-circuit protection and a self-recovering over-temperature (thermal) protection. Charge Pump Operation The AAT3183 step-down charge pump is implemented using a fixed 1/2x (gain) converter topology. This configuration allows efficient energy transfer with a single ceramic flying capacitor. The arrangement of the internal switches requires that the voltage on the flying capacitor is greater than the output voltage plus the input voltage headroom to account for a parasitic voltage drop. Energy is transferred to the flying capacitor and output during alternate `charge' and `discharge' intervals. The amount of energy transferred from the input voltage source to flying capacitor is proportional to the differential voltage across the flying capacitor (VDIFF = VIN - VOUT) which occurs during the `charge' interval multiplied by the switching frequency. The step-down charge pump transfers energy to the output during both the `charge' and `discharge' intervals. Figure 1 illustrates the energy transfer mechanism during `charge' and `discharge' intervals. PFM control compensates for changes in the input voltage and output current by modulating the frequency of switching intervals to maintain the desired output voltage. The output voltage is sensed through an internal resistor divider and compared against a reference voltage by an error amplifier. As the output voltage decreases, POUT = P IN = (VOUT * IOUT) (VIN * IIN) With a constant output current and 1/2x (gain) operation, the input current is constant regardless of input voltage. The input current is equal to 50% [1/2x (gain)] of the output current. A conventional LDO regulator maintains input current which is equal to the output current. Operation efficiency () of an LDO regulator is as follows: IIN = 1/2IOUT (VOUT * IOUT) = (V * 1/2I ) IN OUT = 2 * VOUT VIN ENERGY TRANSFER CFLY(CHARGE) VDIFF VOUT ENERGY TRANSFER VOUT VIN COUT IOUT RLOAD CFLY(DISCHARGE) VIN COUT IOUT RLOAD GND GND Figure 1a: Step-Down Charge Pump "CHARGE" Interval. Figure 1b: Step-Down Charge Pump "DISCHARGE" Interval. 3183.2008.02.1.3 www.analogictech.com 9 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter 0.4V). When EN is connected to a voltage greater than 1.4V (minimum), the AAT3183 will initiate soft-start and resume normal operation. The product features built-in soft-start circuitry to reduce inrush current and eliminate output voltage overshoot. The soft-start circuitry is enabled when input UVLO conditions are satisfied and the EN voltage is high (VEN 1.4V). If EN is tied to IN, the soft start is initiated when UVLO conditions are satisfied. The soft-start circuitry ramps up the output voltage in a controlled manner and minimizes output overshoot. Start-up time from EN positive transitioning (VEN: 0.4V to 1.4V) to output (VOUT) in regulation is 100s (typical). Therefore, the AAT3183 provides a 100% efficiency improvement over conventional LDO regulators, as illustrated in Figure 2. 90 80 AAT3183 Efficiency (%) 70 60 50 40 30 20 10 0 LDO 50 100 150 200 250 300 Output Current (mA) Thermal and Short-Circuit Protection High device temperature may result at elevated ambient temperatures or in cases where high output current causes self heating of the device. The device will disable all switching of the charge pump when the internal junction temperature exceeds 150C (typical). The device will restart and enable the soft-start sequence when the temperature is reduced 15C. This hysteresis ensures that the absolute device temperature is maintained below the over-temperature threshold and protects the device from damage. In the event of a short circuit, an internal current limit is activated and limits the output current to 1A (typical). This current is maintained until the output fault condition is removed or device over-temperature is reached. Under sustained short-circuit conditions, the device will typically reach over-temperature and latch off. The device will cool down after a short period and continue to oscillate between active and over-temperature protection states until the fault is removed. Under these worst case conditions, the device average junction temperature will be less than 150C. Figure 2: AAT3183 Efficiency Comparison vs. LDO. Under-Voltage Lockout Under-voltage lockout (UVLO) circuitry monitors the input voltage (VIN) and ensures that the device will remain in standby (VOUT = 0V) until a valid VIN is present. When VIN is less than 1.5V (typical), the input current is less than 1A and the output voltage (VOUT) remains at 0V, regardless of the status of the enable pin (EN). Typically, the UVLO turn-on threshold is 150mV greater than the UVLO turn-off threshold. UVLO hysteresis minimizes spurious under-voltage detection and eliminates output glitches. Shutdown and Soft-Start The AAT3183 offers an enable pin (EN). When VEN is below 0.4V (maximum), the device is in standby (shutdown) mode and draws less than 1A of input current. The output will remain at 0V when EN voltage is low (VEN 10 www.analogictech.com 3183.2008.02.1.3 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter vide similar performance over the extended temperature range of -55C to +125C. Initial tolerance of 10% is recommended. MLC capacitors offer superior size (high energy density), low equivalent series resistance (ESR), and low equivalent series inductance (ESL) when compared to tantalum and aluminum electrolytic capacitor varieties. In addition, MLC capacitors are not polarized, which simplifies placement on the printed circuit board. Negligible circuit losses and fast charge/discharge rates are possible with MLC capacitors due to their low ESR, which is typically less than 10m. Switching noise is minimized due to their low ESL which produces voltage spikes due to the fast switching current events in charge pump converters. ESL is typically less than 1nH in MLC capacitors. MLC capacitance is reduced with an increasing DC bias voltage. Capacitance derating varies with case size, voltage rating and vendor. It is recommended that circuit performance, including output current capability and input/output voltage ripple, be verified under worst-case operating conditions. The capacitor combinations listed in Table 1 are suitable for output currents up to 220mA and 300mA. Smaller capacitors may be considered for applications requiring less than 300mA output current. Smaller solution size can be achieved at the cost of increased input and output voltage ripple and decreased output current capability. CIN, CFLY and COUT should be located close to the AAT3183 device in order to minimize stray parasitics, specifically ESR and ESL due to PCB layout traces. See the "PCB Layout Guidelines" section of this datasheet for details. An input capacitor (CIN) is required to maintain low input voltage ripple as well as minimize noise coupling to nearby circuitry. The size of the required input capacitor can vary, and depends on the source impedance of the input voltage source. A small 1F to 2.2F MLC input capacitor is suitable in most applications. MLC capacitors sized as small as 0402 are available which meet these requirements. The flying capacitor (CFLY) transfers energy to the output during both `charge' and `discharge' intervals. CFLY is sized to maintain the maximum output load and maintain acceptable output voltage ripple at the minimum input voltage. The ratio COUT to CFLY is determined by the input to output voltage ratio and should be maintained near 5:1 for best performance across the operating range. Applications Information Input Voltage Headroom The input voltage headroom is the required minimum input voltage in excess of 2x the output voltage. The following equation can be used to calculate the required input voltage headroom: VHR = (IOUT * ROUT) M VHR: Input Voltage Headroom IOUT: Output Current ROUT: Output Impedance (see "Output Impedance vs. Input Voltage" performance graph in the "Typical Characteristics" section of this datasheet) M: Charge Pump Gain [AAT3183: 1/2] Design Example: AAT3183 Application Conditions: IOUT = 200mA (max) VOUT = 1.5V What is the required minimum input voltage? Analysis: Minimum Input Voltage: VIN(MIN) = VHR + 2 * VOUT Input Voltage Headroom: VHR = (IOUT * ROUT) M (0.2A * 1) = 0.4V 1/2 = Output Voltage: VOUT = 1.5V Minimum Input Voltage: VIN(MIN) = 0.4V + 2 * 1.5V = 3.4V Solution: The required minimum input voltage is 3.4V. Capacitor Selection The AAT3183 requires three external capacitors; CIN, CFLY and COUT. The capacitor size and type can have a significant impact on charge pump performance, including input and output ripple, stability and operating efficiency. Surface-mount X5R multi-layer ceramic (MLC) capacitors are a suitable choice due to their small size and 15% capacitance tolerance over the -55C to +85C operating temperature range. X7R MLC capacitors pro- 3183.2008.02.1.3 www.analogictech.com 11 PRODUCT DATASHEET AAT3183 ChargePump Input Capacitor Size 0402 0603 TM 300mA Inductorless Step-Down Converter Output Capacitor Size 0603 0603 CIN (F/V) 2.2/6.3 4.7/6.3 COUT (F/V) 2.2/6.3 4.7/6.3 Input [1F(min)] and Flying Capacitors Size 0402 0402 CFLY (F/V) 0.47/10 1/10 Maximum Output Current IOUT (mA) 220 300 Table 1: AAT3183 Capacitor Size Selection Chart (see Table 2 for corresponding manufacturer part numbers). Input and Output Capacitors CIN/COUT Value 2.2F 4.7F 2.2F 4.7F 2.2F 4.7F Input [1F(min)] and Flying Capacitors CFLY Value 0.47F 1F 0.47F 1F 0.47F 1F Voltage (size) 16V (0603) 10V (0603) 16V (0603) 6.3V (0603) 16V (0603) 10V (0603) Mfg TDK TDK Murata Murata Taiyo-Yuden Taiyo-Yuden Part Number C1608X5R1C225K C1608X5R1A475K GRM188R61C225K GRM188R60J475K EMK107BJ225KA LMK107BJ475KA Voltage (size) 10V 10V 10V 10V 10V 16V (0402) (0402) (0402) (0402) (0402) (0603) Mfg TDK TDK Murata Murata Taiyo-Yuden Taiyo-Yuden Part Number C1005X5R1A474K C1005X5R1A105K GRM155R61A474K GRM155R61A105K LMK105BJ474KV EMK107BJ105KA Table 2: Ceramic Capacitors for the 300mA AAT3183 Step-Down Charge Pump Converter. Input and Output Voltage Ripple: Charge Pump Operation The AAT3183 minimizes switching noise with PFM control. PFM switches only when required to maintain the output load, reducing the total switching noise. PFM control generates a small amount of VIN and VOUT regulation ripple (VPFM) due to the charge and discharge of the input and output capacitors. Additional voltage ripple is due to the parasitic resistance and inductance distributed on circuit traces and within the input, fly, and output capacitors themselves; see Figure 3 for the graphic illustration of the AC parasitic components of a AAT3183 typical application circuit. During the charge pump switching events, an AC current path (IAC) is established from the voltage source (VIN) and input capacitor (CIN) through the flying capacitor (CFLY) to the output capacitor (COUT) and returning through the ground plane (GND). The AC voltage ripple signal is measured across CIN and COUT and is highest at full load and high VIN. These AC currents charge and discharge the flying capacitor and flow through the ESR and ESL, which are parasitic elements within the capacitors. Circuit board traces can add to ESR and ESL and will contribute to the AC voltage ripple. Proper component selection and good layout practice are critical in providing low ripple, low EMI performance. These parasitic elements should be minimized to optimize loop transient response and achieve stable operation. The IAC current from the flying capacitor flows through parasitic ESR and ESL. Voltage ripple across the input and output capacitors due to ESR and ESL are approximated: VESR = ESRTOT * IAC VESL = (ESLTOT * IAC) tRISE-FALL The total AC voltage ripple (VRIPPLE) is the sum of the individual AC voltage ripple signals. VRIPPLE = VESR + VESL + VPFM Due to fast switching, a large amount of AC switching noise due to the parasitic ESL within the CIN and COUT ceramic capacitors is seen on the output ripple. This noise may be attenuated with a small amount of input and output filtering. 12 www.analogictech.com 3183.2008.02.1.3 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter CFLY LTRACE ESL ESR LTRACE VOUT ESL AAT3183 ESL VIN CIN ESR COUT IAC GND ESR RLOAD Figure 3: AC Parasitic Components of an AAT3183 Typical Application Circuit. Thermal Performance Power de-rating of the AAT3183 is not necessary in most cases due to the low thermal resistance of the SC70JW-8 package, and the limited device losses. Under operating conditions VOUT = 1.5V and IOUT = 300mA, the estimated worst-case operating efficiency () is 68% (VIN = 4.2V). 160C/W. The maximum junction temperature (TJ(MAX)) of the device at 85C ambient is estimated: This is below the maximum recommended device junction temperature of 125C. TJ(MAX) = TAMB(MAX) + (PD * RJA) = 85C + (211.8mW * 160C/W) = 119C P = OUT PIN (VOUT * IOUT) = (V * I ) IN IN Device power dissipation (PD) can be estimated: PCB Layout Guidelines Proper circuit board layout will maximize efficiency while minimizing switching noise and EMI. The following guidelines should be observed when designing the printed circuit board layout for the AAT3183 step-down converter: 1. Place the three external capacitors as close to the AAT3183 device as possible. Maintain the circuit board traces as short and wide as possible. This will minimize noise resulting from parasitic ESR and ESL in the AC current path. Maintain short and wide traces from ground plane to circuit nodes. This will minimize stray parasitics. A good example of an optimal layout for the AAT3183 is the AAT3183 evaluation board shown in Figures 4 and 5. The evaluation board schematic is shown in Figure 6. PD = PIN - POUT = POUT - POUT (1 - ) (1 - 0.68) 0.68 = VOUT * IOUT * = 1.5V * 0.3A * = 211.8mW 2. 3. The typical junction-to-ambient thermal resistance (RJA) of a SC70JW-8 package mounted on an FR4 board is 3183.2008.02.1.3 www.analogictech.com 13 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter Figure 4: AAT3183 Evaluation Board Top Layer. Figure 5: AAT3183 Evaluation Board Bottom Layer. C2 [C FLY] 3 2 C1VIN 4 C1+ OUT 1 IN VOUT C1 [C IN] AAT 3183 5 C3 [C OUT] 6,7,8 R1 EN GND JP1 Figure 6: AAT3183 Evaluation Board Schematic. 14 www.analogictech.com 3183.2008.02.1.3 PRODUCT DATASHEET AAT3183 ChargePump TM 300mA Inductorless Step-Down Converter Ordering Information Output Voltage 1.5V 1.34V Package SC70JW-8 SC70JW-8 Marking1 UJXYY 2PXYY Part Number (Tape and Reel)2 AAT3183IJS-1.5-T1 AAT3183IJS-1.34-T1 All AnalogicTech products are offered in Pb-free packaging. The term "Pb-free" means semiconductor products that are in compliance with current RoHS standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more information, please visit our website at http://www.analogictech.com/about/quality.aspx. Packaging Information SC70JW-8 0.50 BSC 0.50 BSC 0.50 BSC 1.75 0.10 0.225 0.075 2.00 0.20 2.20 0.20 0.048REF 0.85 0.15 0.15 0.05 1.10 MAX 0.100 7 3 0.45 0.10 2.10 0.30 4 4 All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. Advanced Analogic Technologies, Inc. 3230 Scott Boulevard, Santa Clara, CA 95054 Phone (408) 737-4600 Fax (408) 737-4611 (c) Advanced Analogic Technologies, Inc. AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Except as provided in AnalogicTech's terms and conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer's applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders. 3183.2008.02.1.3 www.analogictech.com 0.05 0.05 15 |
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