AD53508

–7–

REV. 0

IN CURRENT FORCE WITH VOLTAGE MEASURE OR

VERIFY CURRENT FORCE

The linearity tests for forcing current at the FORCE pin:

1. The FORCE pin is loaded with a voltage source.

2. The two ranges of CURRENT FORCE ranges (2 mA and

200

µA) correspond to F1 and F2. The endpoints of the

linearity curve are determined by full scale (or LOW), and

the full scale (or HIGH) readings at the same FORCE pin

voltage.

3. Using these endpoints, gain nonlinearity is computed and

tested at the 1/4 scale, 1/2 scale, and 3/4 scale points.

4. Computations for F1 are:

F1

× 0.25 = LOW + 1 × (HIGH – LOW)/4

F1

× 0.50 = LOW + 2 × (HIGH – LOW)/4

F1

× 0.75 = LOW + 3 × (HIGH – LOW)/4

Where LOW = –Full Scale and HIGH = +Full Scale.

The linearity test for measuring voltage is as follows (at the

MEAS_OUT pin):

1. The endpoints of the linearity curve are determined by the

–full scale (or LOW), and the +full scale (or HIGH) readings.

2. Using these endpoints, gain nonlinearity is computed and

tested at the 1/4 scale, 1/2 scale, and 3/4 scale points.

3. Computations for M1 are:

M1

× 0.25 = LOW + 1 × (HIGH – LOW)/4

M1

× 0.50 = LOW + 2 × (HIGH – LOW)/4

M1

× 0.75 = LOW + 3 × (HIGH – LOW)/4

Where LOW = –Full Scale, and HIGH = +Full Scale.

CURRENT FORCE WITH VOLTAGE MEASURE

(2 mA RANGE)

1. DAC1 = 5 V.

2. FORCE pin loaded with 9 V source.

3. Measure current at FORCE.

4. Measure voltage at MEAS_OUT.

6. Measure current at FORCE and compare to 3.

7. Measure voltage at MEAS_OUT and compare to 4.

9. DAC1 = 0 V.

10. FORCE pin loaded with –4 V source.

11. Measure current at FORCE.

12. Measure voltage at MEAS_OUT.

14. Measure current at FORCE and compare to 11.

15. Measure voltage at MEAS_OUT and compare to 12.

VOLTAGE FORCE WITH CURRENT MEASURE

(2 mA RANGE)

1. DAC1 = 9 V.

2. FORCE pin loaded with 2 mA current source.

3. Measure voltage at FORCE.

4. Measure current at MEAS_OUT.

6. Measure voltage at FORCE and compare to 3:

Limit =

±237 µV.

7. Measure current at MEAS_OUT and compare to 4:

Limit =

±237 µV.

9. DAC1 = –4 V.

10. FORCE pin loaded with 2 mA current sink.

11. Measure voltage at FORCE.

12. Measure current at MEAS_OUT.

14. Measure voltage at FORCE and compare to 11:

Limit =

±474 µV.

15. Measure current at MEAS_OUT and compare to 12.

S11

S12

S13

S14

S15

S16

INT/IM

R1

R2

INTEGRATE

S10

UNITY

DIFF

VF

S4

IF

S5

C1

1k

2mA

10k

200 A

EXT RC

SENSE

S8

S9

S2

S3

VM

IM

ENABLE

S1

CON

2.5V

S6

S7

FORCING

VOLTAGE

DAC1

DAC2

DSR

MEAS OUT

40pF

S17

GUARD

FORCE

SENSE

R

R

1.25R

1.25R

MAIN

GUARD

S18

AD53508

OUTPUT

≤ 2 mA