AD1376/AD1377

–6–

REV. B

CALIBRATION

(14-Bit Resolution Examples)

External ZERO ADJ and GAIN ADJ potentiometers, connected

as shown in Figures 4 and 5, are used for device calibration. To

prevent interaction of these two adjustments, Zero is always

adjusted first and then Gain. Zero is adjusted with the analog

input near the most negative end of the analog range (0 for

unipolar and –FS for bipolar input ranges). Gain is adjusted

with the analog input near the most positive end of the analog

range.

0 V to + 10 V Range

digital output = 11111111111110.

Zero is now calibrated. Set analog input to +FSR – 2 LSB =

+9.99878 V. Adjust Gain for 00000000000001 digital output

code; full scale (Gain) is now calibrated. Half scale calibration

check: set analog input to +5.00000 V; digital output code

should be 01111111111111.

–10 V to + 10 V Range

Set analog input to 9.99878 V; adjust zero for 1111111111110

digital output (complementary offset binary) code. Set analog

input to 9.99756 V; adjust Gain for 00000000000001 digital

output (complementary offset binary) code. Half scale calibra-

tion check set analog input to 0.00000 V; digital output (com-

plementary offset binary) code should be 01111111111111.

Figure 11. Analog and Power Connections for Unipolar

0 V to +10 V Input Range

Table III. Transition Values vs. Calibration Codes

Code Under Test

Low Side Transition Values

MSB

LSB

Range

±10 V

±5 V

±2.5 V

0 V to +10 V

0 V to +5 V

000 ……… 000*

+Full Scale

+10 V

+5 V

+2.5 V

+10 V

+5 V

–3/2 LSB

–3/2 LSB

–3/2 LSB

–3/2 LSB

–3/2 LSB

011……… 111

Mid Scale

0–1/2 LSB

0–1/2 LSB

0–1/2 LSB

+5 V–1/2 LSB

+2.5 V–1/2 LSB

111……… 110

–Full Scale

–10 V

–5 V

–2.5 V

0 V

0 V

+1/2 LSB

+1/2 LSB

+1/2 LSB

+1/2 LSB

+1/2 LSB

*Voltages given are the nominal value for Transition to the code specified.

Note: For LSB value for range and resolution used, see Table IV.

Table IV. Input Voltage Range and LSB Values

Analog Input

Voltage Range

±10 V

±5 V

±2.5 V

0 V to +10 V

0 V to +5 V

Code

COB*

COB*

COB*

Designation

or CTC**

or CTC**

or CTC**

CSB***

CSB***

One Least

FSR

20 V

10 V

5 V

10 V

5 V

Significant

2

n

2

n

2

n

2

n

2

n

2

n

Bit (LSB)

n = 8

78.13 mV

39.06 mV

19.53 mV

39.06 mV

19.53 mV

n = 10

19.53 mV

9.77 mV

4.88 mV

9.77 mV

4.88 mV

n = 12

4.88 mV

2.44 mV

1.22 mV

2.44 mV

1.22 mV

n = 13

2.44 mV

1.22 mV

0.61 mV

1.22 mV

0.61 mV

n = 14

1.22 mV

0.61 mV

0.31 mV

0.61 mV

0.31 mV

n = 15

0.61 mV

0.31 mV

0.15 mV

0.31 mV

0.15 mV

NOTES

product (

MSB).

***CSB = Complementary Straight Binary.