®

ADC76

6

270k

Ω

MSB

1

2

3

4

5

6

7

8

9

10

11

12

13

15

14

NC

16

32

31

30

29

28

27

26

25

24

23

22

21

20

18

19

17

Dotted Lines

Are External

Connections

0.01µF*

Analog Input

±10V

1.8M

Ω

Gain

Adjust

10k

to

100k

Offset

Adjust

Ω

Ω

Status Output to

Control Logic

Serial Out

1µF

+5VDC

+15VDC

1µF

1µF

Analog

Common

–15VDC

Digital

Common

Convert Command From

Control Logic

*Capacitor should be connected even if external gain adjust is not used.

10k

to

100k

Bipolar

Offset

Ω

Ω

ADC76

1µF

2k

Ω

+5

+

+

+

DISCUSSION

OF SPECIFICATIONS

The ADC76 is specified to meet critical performance criteria

for a wide variety of applications. The most critical specifi-

cations for an A/ D converter are linearity, drift, gain and

offset errors, and conversion speed effects on accuracy. This

ADC is factory-trimmed and tested for all critical key

specifications.

GAIN AND OFFSET ERROR

Initial Gain and Offset errors are factory-trimmed to typi-

cally

±0.1% of FSR (±0.05% for unipolar offset) at 25°C.

These errors may be trimmed to zero by connecting external

POWER SUPPLY SENSITIVITY

Changes in the DC power supply voltages will affect accu-

racy. The ADC76 power supply sensitivity is specified at

±0.003% of FSR/%V

of FSR/%V

supplies with 1% or less ripple are recommended for use

with this ADC. See Layout Precautions, Power Supply

LINEARITY ERROR

Linearity error is not adjustable and is the most meaningful

indicator of A/ D converter accuracy. Linearity is the devia-

tion of an actual bit transition from the ideal transition value

at any level over the range of the A/ D converter.

DIFFERENTIAL LINEARITY ERROR

Differential linearity describes the step size between transi-

tion values. A differential linearity error of

±0.003% of FSR

indicates that the size of any step may not vary from the ideal

step size by more than 0.003% of Full Scale Range.

ACCURACY VERSUS SPEED

In successive approximation A/ D converters, the conver-

sion speed affects linearity and differential linearity errors.

Conversion speed and its effect on linearity and differential

FIGURE 6. Linearity Versus Conversion Time.

15

10

Conversion Time (µs)

0.01

0.006

0.003

0.001

Short Cycled to 13 Bits

1/2LSB 14 Bit

Short Cycled to 14 Bits

1/2LSB 13 Bit

11

12

13

14

FIGURE 5. ADC76 Connections for:

±10V Analog Input, 14-Bit Resolution (Short-Cycled), Parallel Data Output.