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3 1/2Digit LCD/LED Display A/D Converters
WS7106 / WS7107
Features
* Guaranteed Zero Reading for 0V Input on All Scales * True Polarity at Zero for Precise Null Detection
Description
The WS7106 and WS7107 are high performance, low power, 31/2 digit A/D converters. Included are seven segment decoders, display drivers, a reference, and a clock. The WS7106 is designed to interface with a liquid crystal display (LCD) and includes a multiplexed backplane drive; the WS 7107 will directly drive an instrument size light emitting diode (LED) display.
* True Differential Input and Reference, Direct Display Drive - LCD WS7106, LED WS7107
* On Chip Clock and Reference
* Low Noise - Less Than 15VP-P
* No Additional Active Circuits Required
* Low Power Dissipation - Typically Less Than 10mW
Ordering Information
PART NO. TEMP. RANGE (oC) PACKAGE
40Ld PDIP
40Ld PDIP
The WS7106 and WS 7107 bring together a combination of high accuracy, versatility, and true economy.True differential inputs and reference are useful in all systems, but give the desiger an uncommon advantage when measuring load cells, strain gauges and other bridge type transducers. Finally, the true economy of single power supply operation (WS7106), enables a high performance panel meter to built with the addition of only 10 passive compoents and a disply.
PKG. NO.
WS7106CPL
WS7107CPL
0 to 70
0 to70
E40.6
E40.6
Pinouts
WS7106CPL (PDIP) WS7107CPL (PDIP)
V+ D1 C1 B1 (1' s) A1 F1 G1 E1 D2 C2 (10' s) B2 A2 F2 E2 D3 (100' s) B3 F3 E3 (1000) AB4 (MINUS) POL 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 40 OSC 1 39 OSC 2 38 OSC 3 37 TEST 36 REF HI 35 REF LO 34 CREF+ 33 CREF32 COMMON 31 IN HI 30 IN LO 29 A-Z 28 BUFF 27 INT 26 V25 G2 (10' s) 24 C3 23 A3 22 G3 21 BP/GND (100' s)
Wing Shing Computer Components Co., (H.K.)Ltd. Homepage: http://www.wingshing.com
Tel:(852)2341 9276 Fax:(852)2797 8153 E-mail: wsccltd@hkstar.com
WS7106/WS710 7
Absolute Maximum Ratings
Supply Voltage WS7106, V+ to V-..................................15v WS7107, V+ to GND...............................6V WS7107, V_ to GND......................... ....-9V Analog Input Voltage (Either Input) (Note 1)V+ to VReference Input Voltage (Either Input)V+ to VClock Input WS7106TEST to V+ WS7107GND to V+
Thermal Information
Thermal Resistance (typical, Note 2) JA(/W) 50
PDIP Package.................................................... ...... ............
Maximum Junction Temperature............................................ .........150 Maximum Storage Temperature Range.................................-65 to 150
Operating Conditions
Temperature Range..............................0 to 70
CAUTION: Stresses above those listed in "absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation Of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
Notes:
1. Input voltages may exceed the supply voltages provided the input current is limited to 100A 2. JA Is measured with the component mounted on an evaluation PC on board in fee air.
Electrical specifications PARAMETER
SYSTEM PERFORMACE Zero Input Reading Ratiometric Reading
(Note 3) TEST CONDITIONS MIN TYP MAX UNIT
VIN=0.0V, FULL Scale = 200mV VIN = VREF, VREF = 100mV -VIN=+VIN=200mV Difference in Reading for Equal Positive and Negative Inputs Near Full Scale Full Scale = 200mV or Full Scale = 2V Maximum Deviation from Best Straight Line Fit (note 6) VCM = 1V, VIN = 0V, Full Scale = 200mv(Note 6) VIN = 0 (Does Not Include LED Current for WS7107 WS7107 Only 25k Between Common and Positive Supply (With Respect to + Supply) VIN=0V Full Scale=200mV VIN=0V 25K between Common and V+ 0-70 VIN=199mV 0-70Ext. ref. 0ppm/ VIN=0V-70
-000.0 999
000.0 999/1000
+000.0 1000
Digital Reading Digital Reading Counts
Rollover Error
-1
0.2
+1
Linearity Common Mode Rejection Ratio End Power Supply Character V+ Supply Current End Power Supply Character V- Supply Current COMMON Pin Analog Common Voltage Noise (PK-PK Value not exceeded 95% of time) Input Leakage Current Analog COMMON Temperature Coefficient Scale Factor Temperature Coefficient Zero Reading Drift
-1 2.4
0.2 50 0.5 0.5 3.0 15 1 60 60 0.2
+1 1.8 1.8 3.2
Counts V/V mA mA V uVP-P
10 75 75 1
pA ppm/ ppm/ uV/
DISPLAY DRIVER WS7106 ONLY
Peak-to-Peak Segment Drive Voltage Peak-to-Peak Backplane Drive Voltage V+ = to V- = 9V (Note 5) 4 5 6 V
2
WS7106 / WS7107
Electrical Specifications
PARAMETER
DISPLAY DRIVER WS7107 ONLY
(Continued) (Note 1) TEST CONDITIONS MIN TYP MAX UNIT
Segment Sinking Current (Except Pins 19 and 20) Pin 19 Only Pin 20 Only
V+ = 5V, Segment Voltage = 3V 5 10 4 8 16 7 mA mA mA
NOTES: 1. Dissipation rating assumes device is mounted with all leads soldered to printed circuit board. 3. 2. Back plane drive is in phase with segment drive for 'off' segment, 180 degrees out of phase for 'on' segment. Frequency is 20 times conversion rate. Average DC component is less than 50mV 3. Not tested, Quaranteed by design.
Typical Applications and Test Circuits
+
R1 R3 OSC 1 40 OSC 2 39 OSC 3 38 C4 TEST 37 R4 C1 R5 C5 C2 R2 C3 DISPLAY
REF HI 36
REF LO 35
CREF+ 34
CREF- 33
COM 32
IN HI 31
IN LO 30
A-Z 29
BUFF 28
INT 27
V- 26
G2 25
C3 24
A3 23
G3 22
WS7106
20 POL 19 AB4 G1 D1 C1 B1 A1 D2 10 C2 11 B2 12 A2 15 D3 16 B3 V+ E1 14 E2 18 E3 F1 13 F2 17 F3
1
2
3
4
5
6
7
8
9
DISPLAY
FIGURE 1. WS 7106 TEST CIRCUIT AND TYPICAL APPLICATION WITH LCD DISPLAY COMPONENTS SELECTED FOR 200mV FULL SCALE
+5V R5 C1 C5 C2 R2 C3 DISPLAY
+
IN
-
-5V
R1 R3 OSC 1 40 OSC 2 39 OSC 3 38 C4 TEST 37 R4
BP 21
REF HI 36
REF LO 35
CREF+ 34
CREF- 33
COM 32
IN HI 31
IN LO 30
A-Z 29
BUFF 28
INT 27
V- 26
G2 25
C3 24
A3 23
G3 22
WS7107
20 POL 19 AB4 G1 D2 10 C2 11 B2 12 A2 15 D3 16 B3 D1 C1 B1 A1 V+ E1 14 E2 18 E3 13 F2 17 F3 F1
1
2
3
4
5
6
7
8
9
DISPLAY
FIGURE 2. WS 7107 TEST CIRCUIT AND TYPICAL APPLICATION WITH LED DISPLAY COMPONENTS SELECTED FOR 200mV FULL SCALE
3
GND 21
C1 = 0.1F C2 = 0.47F C3 = 0.22F C4 = 100pF C5 = 0.02F R1 = 24k R2 = 47k R3 = 100k R4 = 1k R5 = 1M C1 = 0.1F C2 = 0.47F C3 = 0.22F C4 = 100pF C5 = 0.02F R1 = 24k R2 = 47k R3 = 100k R4 = 1k R5 = 1M
+
IN
-
9V
WS7106 / WS7107
Design Information Summary Sheet
* OSCILLATOR FREQUENCY fOSC = 0.45/RC COSC > 50pF; ROSC > 50k fOSC (Typ) = 48kHz * OSCILLATOR PERIOD tOSC = RC/0.45 * INTEGRATION CLOCK FREQUENCY fCLOCK = fOSC/4 * INTEGRATION PERIOD tINT = 1000 x (4/fOSC) * 60/50Hz REJECTION CRITERION tINT/t60Hz or tlNT/t60Hz = Integer * OPTIMUM INTEGRATION CURRENT IINT = 4A * FULL SCALE ANALOG INPUT VOLTAGE VlNFS (Typ) = 200mV or 2V * INTEGRATE RESISTOR
V INFS R INT = ---------------I INT
* DISPLAY COUNT
V IN COUNT = 1000 x -------------V REF
* CONVERSION CYCLE tCYC = tCL0CK x 4000 tCYC = tOSC x 16,000 when fOSC = 48kHz; tCYC = 333ms * COMMON MODE INPUT VOLTAGE (V- + 1V) < VlN < (V+ - 0.5V) * AUTO-ZERO CAPACITOR 0.01F < CAZ < 1F * REFERENCE CAPACITOR 0.1F < CREF < 1F * VCOM Biased between Vi and V-. * VCOM V+ - 2.8V Regulation lost when V+ to V- < 6.8V If VCOM is externally pulled down to (V+ to V-)/2, the VCOM circuit will turn off. WS 7106 POWER SUPPLY: SINGLE 9V V+ - V- = 9V Digital supply is generated internally VGND V+ - 4.5V * WS7106 DISPLAY: LCD Type: Direct drive with digital logic supply amplitude. _ * WS7107 POWER SUPPLY: DUAL +5.0V V+ = +5V to GND V- = -5V to GND Digital Logic and LED driver supply V+ to GND * WS7107 DISPLAY: LED Type: Non-Multiplexed Common Anode
* INTEGRATE CAPACITOR
( t INT ) ( I INT ) C INT = ------------------------------V INT
* INTEGRATOR OUTPUT VOLTAGE SWING
( t INT ) ( I INT ) V INT = ------------------------------C INT
* VINT MAXIMUM SWING: (V- + 0.5V) < VINT < (V+ - 0.5V), VINT (Typ) = 2V
Typical Integrator Amplifier Output Waveform (INT Pin)
AUTO ZERO PHASE (COUNTS) 2999 - 1000
SIGNAL INTEGRATE PHASE FIXED 1000 COUNTS
DE-INTEGRATE PHASE 0 - 1999 COUNTS
TOTAL CONVERSION TIME = 4000 x tCLOCK = 16,000 x tOSC
4
WS7106 / WS7107
Detailed Description
Analog Section Figure 3 shows the Analog Section for the WS7106 and WS7107. Each measurement cycle is divided into three phases. They are (1) auto-zero (A-Z), (2) signal integrate (INT) and (3) de-integrate (DE). Auto-Zer o Phase During auto-zero three things happen. First, input high and low are disconnected from the pins and internally shorted to analog COMMON. Second, the reference capacitor is charged to the reference voltage. Third, a feedback loop is closed around the system to charge the auto-zero capacitor CAZ to compensate for offset voltages in the buffer amplifier, integrator, and comparator. Since the comparator is included in the loop, the A-Z accuracy is limited only by the noise of the system. In any case, the offset referred to the input is less than 10V. Signal Integrate Phase During signal integrate, the auto-zero loop is opened, the internal short is removed, and the internal input high and low are connected to the external pins. The converter then integrates the differential voltage between IN HI and IN LO for a fixed time. This differential voltage can be within a wide common mode range: up to 1V from either supply. If, on the other hand, the input signal has no return with respect to the converter power supply, IN LO can be tied to analog COMMON to establish the correct common mode voltage. At the end of this phase, the polarity of the integrated signal is determined. De-Integrate Phase The final phase is de-integrate, or reference integrate. Input low is internally connected to analog COMMON and input high is connected across the previously charged reference capacitor. Circuitry within the chip ensures that the capacitor will be connected with the correct polarity to cause the integrator output to return to zero. The time required for the output to return to zero is proportional to the input signal. Specifically the digital reading displayed is:
V IN DISPLAY COUNT = 1000 -------------- . V REF
Differential Input The input can accept differential voltages anywhere within the common mode range of the input amplifier, or specifically from 0.5V below the positive supply to 1V above the negative supply. In this range, the system has a CMRR of 86dB typical. However, care must be exercised to assure the integrator output does not saturate. A worst case condition would be a large positive common mode voltage with a near full scale negative differential input voltage. The negative input signal drives the integrator positive when most of its swing has been used up by the positive common mode voltage. For these critical applications the integrator output swing can be reduced to less than the recommended 2V full scale swing with little loss of accuracy. The integrator output can swing to within 0.3V of either supply without loss of linearity.
STRAY
CREF
STRAY RINT CAZ A-Z 29 INTEGRATOR
+
CINT INT 27
CREF+ V+ 34
REF HI 36 A-Z
REF LO 35 A-Z
CREF 33
BUFFER V+ 28 1
+
-
10A 31 IN HI INT DEDE+ INPUT HIGH 6.2V 2.8V
-
+
-
TO DIGITAL SECTION
A-Z
A-Z N 32 COMMON INT 30 IN LO VA-Z AND DE() INPUT LOW DE+ DE+
-
COMPARATOR
FIGURE 3. ANALOG SECTION OF WS7106 AND WS7107
5
WS7106 / WS7107
Differential Reference The reference voltage can be generated anywhere within the power supply voltage of the converter. The main source of common mode error is a roll-over voltage caused by the reference capacitor losing or gaining charge to stray capacity on its nodes. If there is a large common mode voltage, the reference capacitor can gain charge (increase voltage) when called up to de-integrate a positive signal but lose charge (decrease voltage) when called up to de-integrate a negative input signal. This difference in reference for positive or negative input voltage will give a roll-over error. However, by selecting the reference capacitor such that it is large enough in comparison to the stray capacitance, this error can be held to less than 0.5 count worst case. (See Component Value Selection.) Analog COMMON This pin is included primarily to set the common mode voltage for battery operation (WS7106) or for any system where the input signals are floating with respect to the power supply. The COMMON pin sets a voltage that is approximately 2.8V more negative than the positive supply. This is selected to give a minimum end-of-life battery voltage of about 6V. However, analog COMMON has some of the attributes of a reference voltage. When the total supply voltage is large enough to cause the zener to regulate (>7V), the COMMON voltage will have a low voltage coefficient (0.001%/V), low output impedance (15), and a temperature coefficient typically less than 80ppm/oC. The limitations of the on chip reference should also be recognized, however. With the WS7107, the internal heating which results from the LED drivers can cause some degradation in performance. Due to their higher thermal resistance, plastic parts are poorer in this respect than ceramic. The combination of reference Temperature Coefficient (TC), internal chip dissipation, and package thermal resistance can increase noise near full scale from 25V to 80VP-P. Also the linearity in going from a high dissipation count such as 1000 (20 segments on) to a low dissipation count such as 1111(8 segments on) can suffer by a count or more. Devices with a positive TC reference may require several counts to pull out of an over-range condition. This is because over-range is a low dissipation mode, with the three least significant digits blanked. Similarly, units with a negative TC may cycle between over-range and a non-over-range count as the die alternately heats and cools. All these problems are of course eliminated if an external reference is used.
The WS 7106, with its negligible dissipation, suffers from none of these problems. In either case, an external reference can easily be added, as shown in Figure 4.
should be since this removes the common mode voltage from the reference system. Within the lC, analog COMMON is tied to an N-Channel FET that can sink approximately 30mA of current to hold the voltage 2.8V below the positive supply (when a load is trying to pull the common line positive). However, there is only 10A of source current, so COMMON may easily be tied to a more negative voltage thus overriding the internal reference.
V+
V REF HI REF LO 6.8V ZENER IZ
WS7106 WS7107
V-
FIGURE 4A.
V+
V
6.8k 20k
WS7106 WS7107
REF HI REF LO COMMON
ICL8069 1.2V REFERENCE
FIGURE 4B. FIGURE 4. USING AN EXTERNAL REFERENCE
TEST The TEST pin serves two functions. On the WS7106 it is coupled to the internally generated digital supply through a 500 resistor. Thus it can be used as the negative supply for externally generated segment drivers such as decimal points or any other presentation the user may want to include on the LCD display. Figures 5 and 6 show such an application. No more than a 1mA load should be applied.
V+
1M TO LCD DECIMAL POINT
Analog COMMON is also used as the input low return during auto-zero and de-integrate. If IN LO is different from analog COMMON, a common mode voltage exists in the system and is taken care of by the excellent CMRR of the converter. However, in some applications IN LO will be set at a fixed known voltage (power supply common for instance). In this application, analog COMMON should be tied to the same point, thus removing the common mode voltage from the converter. The same holds true for the reference voltage. If reference can be conveniently tied to analog COMMON, it
WS7106
BP TEST 21 37
TO LCD BACKPLANE
FIGURE 5. SIMPLE INVERTER FOR FIXED DECIMAL POINT
6
WS7106 / WS7107
The second function is a "lamp test". When TEST is pulled high (to V+) all segments will be turned on and the display should read "1888". The TEST pin will sink about 15mA under these conditions.
CAUTION: In the lamp test mode, the segments have a constant DC voltage (no square-wave). This may burn the LCD display if maintained for extended periods.
Digital Section
Figures 7 and 8 show the digital section for the WS7106 and WS7107, respectively. In the WS7106 , an internal digital ground is generated from a 6V Zener diode and a large P-Channel source follower. This supply is made stiff to absorb the relative large capacitive currents when the back plane (BP) voltage is switched. The BP frequency is the clock frequency divided by 800. For three readings/sec., this is a 60Hz square wave with a nominal amplitude of 5V. The segments are driven at the same frequency and amplitude and are in phase with BP when OFF, but out of phase when ON. In all cases negligible DC voltage exists across the segments. Figure 8 is the Digital Section of the WS7107. It is identical to the WS 7106 except that the regulated supply and back plane drive have been eliminated and the segment drive has been increased from 2mA to 8mA, typical for instrument size common anode LED displays. Since the 1000 output (pin 19) must sink current from two LED segments, it has twice the drive capability or 16mA. In both devices, the polarity indication is "on" for negative analog inputs. If IN LO and IN HI are reversed, this indication can be reversed also, if desired.
a a b f g e d c b c f g e d c e d
21 LCD PHASE DRIVER 7 SEGMENT DECODE 7 SEGMENT DECODE 7 SEGMENT DECODE
V+ V+ BP
WS7106
DECIMAL POINT SELECT
TO LCD DECIMAL POINTS
TEST CD4030 GND
FIGURE 6. EXCLUSIVE `OR' GATE FOR DECIMAL POINT DRIVE
a b f
a b g c
BACKPLANE
TYPICAL SEGMENT OUTPUT V+ 0.5mA SEGMENT OUTPUT 2mA 1000's COUNTER INTERNAL DIGITAL GROUND TO SWITCH DRIVERS FROM COMPARATOR OUTPUT CLOCK
/200
LATCH
100's COUNTER
10's COUNTER
1's COUNTER
1 V+
THREE INVERTERS
ONE INVERTER SHOWN FOR CLARITY
/4
INTERNAL DIGITAL GROUND
LOGIC CONTROL
6.2V 500 TEST
VTH = 1V
37
26 40 OSC 1 OSC 2 39 OSC 3 38
V-
FIGURE 7. WS 7106 DIGITAL SECTION
7
WS7106 / WS7107
a a b f g e d c b c f g e d c e d a b f g c a b
7 SEGMENT DECODE TYPICAL SEGMENT OUTPUT V+ 0.5mA TO SEGMENT 8mA DIGITAL GROUND TO SWITCH DRIVERS FROM COMPARATOR OUTPUT V+ CLOCK /4 1000's COUNTER 100's COUNTER
7 SEGMENT DECODE
7 SEGMENT DECODE
LATCH
10's COUNTER
1's COUNTER
1 V+ LOGIC CONTROL 500 27 DIGITAL GROUND 37 TEST
THREE INVERTERS ONE INVERTER SHOWN FOR CLARITY
40 OSC 1 OSC 2 39 OSC 3 38
FIGURE 8. WS 7107 DIGITAL SECTION
System Timing Figure 9 shows the clocking arrangement used in the WS7106 and WS7107 . Two basic clocking arrangements can be used: 1. Figure 9A. An external oscillator connected to pin 40. 2. Figure 9B. An R-C oscillator using all three pins. The oscillator frequency is divided by four before it clocks the decade counters. It is then further divided to form the three convert-cycle phases. These are signal integrate (1000 counts), reference de-integrate (0 to 2000 counts) and auto-zero (1000 to 3000 counts). For signals less than full scale, auto-zero gets the unused portion of reference de-integrate. This makes a complete measure cycle of 4,000 counts (16,000 clock pulses) independent of input voltage. For three readings/second, an oscillator frequency of 48kHz would be used. To achieve maximum rejection of 60Hz pickup, the signal integrate cycle should be a multiple of 60Hz. Oscillator frequencies of 240kHz, 120kHz, 80kHz, 60kHz, 48kHz, 40kHz, 331/3kHz, etc. should be selected. For 50Hz rejection, Oscillator frequencies of 200kHz, 100kHz, 662/3kHz, 50kHz, 40kHz, etc. would be suitable. Note that 40kHz (2.5 readings/second) will reject both 50Hz and 60Hz (also 400Hz and 440Hz).
40 39 38 INTERNAL TO PART
/4
CLOCK
GND WS7107 TEST WS7106
FIGURE 9A.
INTERNAL TO PART
/4
CLOCK
40
39 R
38 C RC OSCILLATOR
FIGURE 9B. FIGURE 9. CLOCK CIRCUITS
8
WS7106 / WS7107
Component Value Selection
Integrating Resistor Both the buffer amplifier and the integrator have a class A output stage with 100A of quiescent current. They can supply 4A of drive current with negligible nonlinearity. The integrating resistor should be large enough to remain in this very linear region over the input voltage range, but small enough that undue leakage requirements are not placed on the PC board. For 2V full scale, 470k is near optimum and similarly a 47k for a 200mV scale. Integrating Capacitor The integrating capacitor should be selected to give the maximum voltage swing that ensures tolerance buildup will not saturate the integrator swing (approximately. 0.3V from either supply). In the WS7106 or the WS7107, When the analog COMMON is used as a reference, a nominal +2V fullscale integrator swing is fine. For the WS7107 with +5V supplies and analog COMMON tied to supply ground, a 3.5V to +4V swing is nominal. For three readings/second (48kHz clock) nominal values for ClNT are 0.22F and 0.10F, respectively. Of course, if different oscillator frequencies are used, these values should be changed in inverse proportion to maintain the same output swing. An additional requirement of the integrating capacitor is that it must have a low dielectric absorption to prevent roll-over errors. While other types of capacitors are adequate for this application, polypropylene capacitors give undetectable errors at reasonable cost. Auto-Zero Capacitor The size of the auto-zero capacitor has some influence on the noise of the system. For 200mV full scale where noise is very important, a 0.47F capacitor is recommended. On the 2V scale, a 0.047F capacitor increases the speed of recovery from overload and is adequate for noise on this scale. Reference Capacitor A 0.1F capacitor gives good results in most applications. However, where a large common mode voltage exists (i.e., the REF LO pin is not at analog COMMON) and a 200mV scale is used, a larger value is required to prevent roll-over error. Generally 1F will hold the roll-over error to 0.5 count in this instance. Oscillator Components For all ranges of frequency a 100k resistor is recommended and the capacitor is selected from the equation:
0.45 f = ---------- For 48kHz Clock (3 Readings/sec), RC C = 100pF.
V- = 3.3V V+ CD4009 V+ OSC 1 OSC 2 OSC 3 IN914 + 10 F
Reference Voltage The analog input required to generate full scale output (2000 counts) is: VlN = 2VREF. Thus, for the 200mV and 2V scale, VREF should equal 100mV and 1V, respectively. However, in many applications where the A/D is connected to a transducer, there will exist a scale factor other than unity between the input voltage and the digital reading. For instance, in a weighing system, the designer might like to have a full scale reading when the voltage from the transducer is 0.662V. Instead of dividing the input down to 200mV, the designer should use the input voltage directly and select VREF = 0.341V. Suitable values for integrating resistor and capacitor would be 1 20k and 0.22F. This makes the system slightly quieter and also avoids a divider network on the input. The WS 7107 with 5V supplies can accept input signals up to 4V. Another advantage of this system occurs when a digital reading of zero is desired for VIN 0. Temperature and weighing systems with a variable fare are examples. This offset reading can be conveniently generated by connecting the voltage transducer between IN HI and COMMON and the variable (or fixed) offset voltage between COMMON and IN LO.
WS7107 Power Supplies
The WS 7107 is designed to work from 5V supplies. However, if a negative supply is not available, it can be generated from the clock output with 2 diodes, 2 capacitors, and an inexpensive lC. Figure 10 shows this application. See ICL7660 data sheet for an alternative.
In fact, in selected applications no negative supply is required. The conditions to use a single +5V supply are: 1. The input signal can be referenced to the center of the common mode range of the converter. 2. The signal is less than 1.5V. 3. An external reference is used.
0.047 F IN914
-
WS7107
GND V-
FIGURE 10. GENERATING NEGATIVE SUPPLY FROM +5V
9
WS7106 / WS7107
TYPICAL APPLICATIONS
The WS7106 and WS7107 may be used in a wide variety of configurations. The circuits which follow show some of the possibilities, and serve to illustrate the exceptional versatility of these A/D converters.
Typical Applications
TO PIN 1 OSC 1 40 OSC 2 39 OSC 3 38 TEST 37 REF HI 36 REF LO 35 CREF 34 CREF 33 COMMON 32 IN HI 31 IN LO 30 A-Z 29 BUFF 28 INT 27 V - 26 G2 25 C3 24 A3 23 G3 22 BP 21 TO BACKPLANE TO DISPLAY 0.22F 0.01F 0.47F 47k 1k 0.1F 1M + IN 22k 100pF SET VREF = 100mV 100k OSC 1 40 OSC 2 39 OSC 3 38 TEST 37 REF HI 36 REF LO 35 CREF 34 CREF 33 COMMON 32 IN HI 31 IN LO 30 A-Z 29 BUFF 28 INT 27 V - 26 G2 25 C3 24 A3 23 G3 22 GND 21 0.22F 100pF 100k
TO PIN 1
SET VREF = 100mV +5V 1k 22k
0.1F 1M 0.01F 0.47F 47k + IN
+ 9V
-
-
-5V
TO DISPLAY
Values shown are for 200mV full scale, 3 readings/sec., floating supply voltage (9V battery).
Values shown are for 200mV full scale, 3 readings/sec. IN LO may be tied to either COMMON for inputs floating with respect to supplies, or GND for single ended inputs. (See discussion under Analog COMMON.)
FIGURE 11 WS7106 USING THE INTERNAL REFERENCE
FIGURE 12. WS7107 USING THE INTERNAL REFERENCE
10
WS7106 / WS7107
Typical Applications
OSC 1 40 OSC 2 39 OSC 3 38 TEST 37 REF HI 36 REF LO 35 CREF 34 CREF 33 COMMON 32 IN HI 31 IN LO 30 A-Z 29 BUFF 28 INT 27 V - 26 G2 25 C3 24 A3 23 G3 22 GND 21 TO DISPLAY 0.22F V0.01F 0.47F 47k 1k 0.1F 1.2V (ICL8069) 1M + IN 10k 10k V+ 100pF SET VREF = 100mV
(Continued)
TO PIN 1 TO PIN 1 OSC 1 40 OSC 2 39 OSC 3 38 TEST 37 REF HI 36 REF LO 35 CREF 34 CREF 33 COMMON 32 IN HI 31 IN LO 30 A-Z 29 BUFF 28 INT 27 V - 26 G2 25 C3 24 A3 23 G3 22 GND 21 TO DISPLAY 0.22F -5V 0.01F 0.47F 47k 1k 0.1F 1M 100k 6.8V + IN +5V 100pF SET VREF = 100mV 100k
100k
-
-
IN LO is tied to supply COMMON establishing the correct common mode voltage. If COMMON is not shorted to GND, the input voltage may float with respect to the power supply and COMMON acts as a pre-regulator for the reference. If COMMON is shorted to GND, the input is single ended (referred to supply GND) and the pre-regulator is overridden.
FIGURE 13. WS 7107 WITH AN EXTERNAL BAND-GAP REFERENCE (1.2V TYPE)
TO PIN 1 OSC 1 40 OSC 2 39 OSC 3 38 TEST 37 REF HI 36 REF LO 35 CREF 34 CREF 33 COMMON 32 IN HI 31 IN LO 30 A-Z 29 BUFF 28 INT 27 V - 26 G2 25 C3 24 A3 23 G3 22 BP/GND 21 TO DISPLAY 0.22F V0.01F 0.047F 470k 25k 0.1F 1M + IN 24k V+ 100pF SET VREF = 100mV 100k
Since low TC zeners have breakdown voltages ~ 6.8V, diode must be placed across the total supply (10V). As in the case of Figure 14, IN LO may be tied to either COMMON or GND.
FIGURE 14. WS 7107 WITH ZENER DIODE REFERENCE
TO PIN 1 OSC 1 40 OSC 2 39 OSC 3 38 TEST 37 REF HI 36 REF LO 35 CREF 34 CREF 33 COMMON 32 IN HI 31 IN LO 30 A-Z 29 BUFF 28 INT 27 V - 26 G2 25 C3 24 A3 23 G3 22 GND 21 TO DISPLAY 0.22F 0.01F 0.47F 47k 1k 0.1F 1.2V (ICL8069) 1M + IN 10k 15k +5V 100pF SET VREF = 100mV 100k
-
-
An external reference must be used in this application, since the voltage between V+ and V- is insufficient for correct operation of the internal reference.
FIGURE 15. WS7106 AND WS7107; RECOMMENDED COMPONENT VALUES FOR 2V FULL SCALE
FIGURE 16. WS7107 OPERATED FROM SINGLE +5V
11
WS7106 / WS7107
Typical Applications
OSC 1 40 OSC 2 39 OSC 3 38 TEST 37 REF HI 36 REF LO 35 CREF 34 CREF 33 COMMON 32 IN HI 31 IN LO 30 A-Z 29 BUFF 28 INT 27 V - 26 G2 25 C3 24 A3 23 G3 22 GND 21 TO DISPLAY 0.22F 47k 0.47F 0.1F 100pF 100k
(Continued)
TO PIN 1 V+ TO PIN 1 OSC 1 40 OSC 2 39 OSC 3 38 TEST 37 REF HI 36 REF LO 35 CREF 34 CREF 33 COMMON 32 IN HI 31 IN LO 30 A-Z 29 BUFF 28 INT 27 V - 26 G2 25 C3 24 A3 23 G3 22 BP 21 TO BACKPLANE TO DISPLAY 0.22F 0.01F 0.47F 47k 9V ZERO ADJUST SILICON NPN MPS 3704 OR SIMILAR 0.1F 100k 1M 100k 220k 100pF SCALE FACTOR ADJUST 22k 100k
The resistor values within the bridge are determined by the desired sensitivity.
A silicon diode-connected transistor has a temperature coefficient of about -2mV/oC. Calibration is achieved by placing the sensing transistor in ice water and adjusting the zeroing potentiometer for a 000.0 reading. The sensor should then be placed in boiling water and the scale-factor potentiometer adjusted for a 100.0 reading.
FIGURE 17. WS 7107 MEASUREING RATIOMETRIC VALUES OF QUAD LOAD CELL
V+ 1 V+ 2 D1 TO LOGIC VCC 3 C1 4 B1 5 A1 6 F1 7 G1 8 E1 9 D2 10 C2 11 B2 12 A2 13 F2 14 E2 15 D3 16 B3 17 F3 O /RANGE 18 E3 19 AB4 20 POL U /RANGE CD4023 OR 74C10 OSC 1 40 OSC 2 39 OSC 3 38 TEST 37 REF HI 36 REF LO 35 TO CREF 34 LOGIC GND CREF 33 IN HI 31 IN LO 30 A-Z 29 BUFF 28 INT 27 V- 26 G2 25 C3 24 A3 23 G3 22 BP 21 V-
FIGURE 18. WS 7106 USED AS A DIGITAL CENTIGRADE THERMOMETER
+5V 1 V+ 2 D1 3 C1 4 B1 5 A1 6 F1 TO LOGIC VCC 12k 7 G1 8 E1 9 D2 10 C2 OSC 1 40 OSC 2 39 OSC 3 38 TEST 37 REF HI 36 REF LO 35 CREF 34 CREF 33 COMMON 32 IN HI 31 IN LO 30 A-Z 29 BUFF 28 INT 27 V- 26 G2 25 C3 24 A3 23 G3 22 BP 21 V-
COMMON 32
The LM339 is required to ensure logic compatibility with heavy display loading.
+
11 B2 12 A2 13 F2 14 E2 15 D3 16 B3
-
O /RANGE
+ +
17 F3 18 E3 19 AB4 20 POL
U /RANGE CD4023 OR 74C10
+ 33k
CD4077
FIGURE 19. CIRCUIT FOR DEVELOPING UNDERRANGE AND OVERRANGE SIGNAL FROM WS7106 OUTPUTS
FIGURE 20. CIRCUIT FOR DEVELOPING UNDERRANGE AND OVERRANGE SIGNALS FROM WS7107 OUTPUT
12
WS7106 / WS7107
Typical Applications
OSC 1 40 OSC 2 39 OSC 3 38 TEST 37 REF HI 36 REF LO 35 CREF 34 CREF 33 COMMON 32 IN HI 31 IN LO 30 A-Z 29 BUFF 28 INT 27 V - 26 G2 25 C3 24 A3 23 G3 22 BP 21 TO BACKPLANE TO DISPLAY 0.22F 47k 10F 0.47F + 9V 1k 0.1F 1F 4.3k 0.22F 100pF (FOR OPTIMUM BANDWIDTH) 10k 1F 10k 1F 22k 470k 2.2M 1N914 100pF
(Continued)
TO PIN 1 100k 10F SCALE FACTOR ADJUST (VREF = 100mV FOR AC TO RMS) 5F CA3140 + 100k
-
AC IN
-
Test is used as a common-mode reference level to ensure compatibility with most op amps. FIGURE 21. AC TO DC CONVERTER WITH WS7106
+5V
DM7407 ICL7107 130
LED SEGMENTS
130 130
FIGURE 22. DISPLAY BUFFERING FOR INCREASED DRIVE CURRENT
13
WS7106 / WS7107
Dual-In-Line Plastic Packages (PDIP)
N E1 INDEX AREA 12 3 N/2
E40.6 (JEDEC MS-011-AC ISSUE B)
40 LEAD DUAL-IN-LINE PLASTIC PACKAGE INCHES SYMBOL
-B-
MILLIMETERS MIN 0.39 3.18 0.356 0.77 0.204 50.3 0.13 15.24 12.32 MAX 6.35 4.95 0.558 1.77 0.381 53.2 15.87 14.73 NOTES 4 4 8 5 5 6 5 6 7 4 9
MIN 0.015 0.125 0.014 0.030 0.008 1.980 0.005 0.600 0.485
MAX 0.250 0.195 0.022 0.070 0.015 2.095 0.625 0.580
A
E A2 L A C L
-AD BASE PLANE SEATING PLANE D1 B1 B 0.010 (0.25) M D1 A1
A1 A2
-C-
B B1 C D D1 E
eA eC
C
e
C A BS
eB
NOTES: 1. Controlling Dimensions: INCH. In case of conflict between English and Metric dimensions, the inch dimensions control. 2. Dimensioning and tolerancing per ANSI Y14.5M-1982. 3. Symbols are defined in the "MO Series Symbol List" in Section 2.2 of Publication No. 95. 4. Dimensions A, A1 and L are measured with the package seated in JEDEC seating plane gauge GS-3. 5. D, D1, and E1 dimensions do not include mold flash or protrusions. Mold flash or protrusions shall not exceed 0.010 inch (0.25mm). 6. E and eA are measured with the leads constrained to be perpendicular to datum -C- . 7. eB and eC are measured at the lead tips with the leads unconstrained. eC must be zero or greater. 8. B1 maximum dimensions do not include dambar protrusions. Dambar protrusions shall not exceed 0.010 inch (0.25mm). 9. N is the maximum number of terminal positions. 10. Corner leads (1, N, N/2 and N/2 + 1) for E8.3, E16.3, E18.3, E28.3, E42.6 will have a B1 dimension of 0.030 - 0.045 inch (0.76 - 1.14mm).
E1 e eA eB L N
0.100 BSC 0.600 BSC 0.115 40 0.700 0.200
2.54 BSC 15.24 BSC 2.93 40 17.78 5.08
14

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