Datasheet AD624 (Analog Devices) - 12
| Fabricante | Analog Devices |
| Descripción | Precision Instrumentation Amplifier |
| Páginas / Página | 16 / 12 — AD624. +INPUT. (–INPUT). G = 100. 225.3. +VS. G = 200. 4445.7. 124. 10k. … |
| Revisión | C |
| Formato / tamaño de archivo | PDF / 397 Kb |
| Idioma del documento | Inglés |
AD624. +INPUT. (–INPUT). G = 100. 225.3. +VS. G = 200. 4445.7. 124. 10k. RG1. G = 500. 80.2. 20k. OUT. VOUT. 9 10. 0.1. F LOW. LEAKAGE. RG2. –INPUT. 12 11. (+INPUT)
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AD624
In many applications complex software algorithms for autozero
50
⍀
+INPUT (–INPUT)
applications are not available. For these applications Figure 42 provides a hardware solution.
G = 100 AD624 225.3
⍀
+VS G = 200 4445.7
⍀
VB 124
⍀
10k
⍀
15 16 RG1 G = 500 80.2
⍀
20k
⍀
10k
⍀
14 RG AD624 V 1 OUT VOUT 9 10 13 0.1
F LOW RG CH 2 20k
⍀
LEAKAGE 10k
⍀
10k
⍀
RG2 1k
⍀
50
⍀
–INPUT –V 12 11 (+INPUT) S AD542 +VS 1/2 AD712 DAC A VDD DATA DB0 V AD7510DIKD SS INPUTS 256:1 DB7 GND CS AD7528 A1 A2 A3 A4 WR 200
s DAC A/DAC B 1/2 ZERO PULSE DAC B AD712
Figure 42. Autozero Circuit The microprocessor controlled data acquisition system shown in Figure 43 includes includes both autozero and autogain capabil- Figure 40. Programmable Output Gain Using a DAC ity. By dedicating two of the differential inputs, one to ground and one to the A/D reference, the proper program calibration
AUTOZERO CIRCUITS
cycles can eliminate both initial accuracy errors and accuracy In many applications it is necessary to provide very accurate errors over temperature. The autozero cycle, in this application, data in high gain configurations. At room temperature the offset converts a number that appears to be ground and then writes effects can be nulled by the use of offset trimpots. Over the that same number (8 bit) to the AD624 which eliminates the operating temperature range, however, offset nulling becomes a zero error since its output has an inverted scale. The autogain problem. The circuit of Figure 41 shows a CMOS DAC operat- cycle converts the A/D reference and compares it with full scale. ing in the bipolar mode and connected to the reference terminal A multiplicative correction factor is then computed and applied to provide software controllable offset adjustments. to subsequent readings.
+VS –INPUT RG2 RG V 1 REF G = 100 AD583 AD624 V V G = 200 OUT AD7507 AD624 IN AD574A G = 500 AGND RG2 RG +INPUT 1 A0 A2 –VS 39k
⍀
V EN A1 –VREF REF –VS 20k
⍀
20k
⍀
+V AD589 S R3 20k
⍀
R5 R 20k
⍀
MSB FB AD7524 LATCH DATA OUT1 C1 +VS R4 1/2 10k
⍀
INPUTS LSB 10k
⍀
AD712 1/2 1/2 AD7524 5k AD712
⍀
AD712 CS DECODE 1/2 WR OUT2 AD712 R6 5k
⍀
CONTROL –VS GND MICRO- ADDRESS BUS PROCESSOR
Figure 41. Software Controllable Offset Figure 43. Microprocessor Controlled Data Acquisition System –12– REV. C
In many applications complex software algorithms for autozero
50
⍀
+INPUT (–INPUT)
applications are not available. For these applications Figure 42 provides a hardware solution.
G = 100 AD624 225.3
⍀
+VS G = 200 4445.7
⍀
VB 124
⍀
10k
⍀
15 16 RG1 G = 500 80.2
⍀
20k
⍀
10k
⍀
14 RG AD624 V 1 OUT VOUT 9 10 13 0.1
F LOW RG CH 2 20k
⍀
LEAKAGE 10k
⍀
10k
⍀
RG2 1k
⍀
50
⍀
–INPUT –V 12 11 (+INPUT) S AD542 +VS 1/2 AD712 DAC A VDD DATA DB0 V AD7510DIKD SS INPUTS 256:1 DB7 GND CS AD7528 A1 A2 A3 A4 WR 200
s DAC A/DAC B 1/2 ZERO PULSE DAC B AD712
Figure 42. Autozero Circuit The microprocessor controlled data acquisition system shown in Figure 43 includes includes both autozero and autogain capabil- Figure 40. Programmable Output Gain Using a DAC ity. By dedicating two of the differential inputs, one to ground and one to the A/D reference, the proper program calibration
AUTOZERO CIRCUITS
cycles can eliminate both initial accuracy errors and accuracy In many applications it is necessary to provide very accurate errors over temperature. The autozero cycle, in this application, data in high gain configurations. At room temperature the offset converts a number that appears to be ground and then writes effects can be nulled by the use of offset trimpots. Over the that same number (8 bit) to the AD624 which eliminates the operating temperature range, however, offset nulling becomes a zero error since its output has an inverted scale. The autogain problem. The circuit of Figure 41 shows a CMOS DAC operat- cycle converts the A/D reference and compares it with full scale. ing in the bipolar mode and connected to the reference terminal A multiplicative correction factor is then computed and applied to provide software controllable offset adjustments. to subsequent readings.
+VS –INPUT RG2 RG V 1 REF G = 100 AD583 AD624 V V G = 200 OUT AD7507 AD624 IN AD574A G = 500 AGND RG2 RG +INPUT 1 A0 A2 –VS 39k
⍀
V EN A1 –VREF REF –VS 20k
⍀
20k
⍀
+V AD589 S R3 20k
⍀
R5 R 20k
⍀
MSB FB AD7524 LATCH DATA OUT1 C1 +VS R4 1/2 10k
⍀
INPUTS LSB 10k
⍀
AD712 1/2 1/2 AD7524 5k AD712
⍀
AD712 CS DECODE 1/2 WR OUT2 AD712 R6 5k
⍀
CONTROL –VS GND MICRO- ADDRESS BUS PROCESSOR
Figure 41. Software Controllable Offset Figure 43. Microprocessor Controlled Data Acquisition System –12– REV. C