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
μ
A) 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.
5. V
CC
= 15 V.
6. Measure current at FORCE and compare to 3.
7. Measure voltage at MEAS_OUT and compare to 4.
8. V
CC
= 15 V.
9. DAC1 = 0 V.
10. FORCE pin loaded with –4 V source.
11. Measure current at FORCE.
12. Measure voltage at MEAS_OUT.
13. V
EE
= –9.5 V.
14. Measure current at FORCE and compare to 11.
15. Measure voltage at MEAS_OUT and compare to 12.
16. V
EE
= –10 V.
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.
5. V
CC
= 14.25 V.
6. Measure voltage at FORCE and compare to 3:
Limit =
±
237
μ
V.
7. Measure current at MEAS_OUT and compare to 4:
Limit =
±
237
μ
V.
8. V
CC
= 15 V.
9. DAC1 = –4 V.
10. FORCE pin loaded with 2 mA current sink.
11. Measure voltage at FORCE.
12. Measure current at MEAS_OUT.
13. V
EE
= –9.5 V.
14. Measure voltage at FORCE and compare to 11:
Limit =
±
474
μ
V.
15. Measure current at MEAS_OUT and compare to 12.
16. V
EE
= –10 V.
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
Figure 3. Guarded Current Force/Voltage Measure, I
RANGE 1
: I
≤
2 mA