ADS-929MM 查看數據表（PDF） - Murata Power Solutions

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ADS-929MM

14-Bit, 2MHz, Low-Power Sampling A/D Converters

Murata Power Solutions 

ADS-929

®

®

CALIBRATION PROCEDURE

(Refer to Figures 2 and 3)

Any offset and/or gain calibration procedures should not be

implemented until devices are fully warmed up. To avoid

interaction, offset must be adjusted before gain. The ranges of

adjustment for the circuit of Figure 2 are guaranteed to

compensate for the ADS-929's initial accuracy errors and may

not be able to compensate for additional system errors.

All fixed resistors in Figure 2 should be metal-film types, and

multiturn potentiometers should have TCR’s of 100ppm/°C or

less to minimize drift with temperature.

A/D converters are calibrated by positioning their digital outputs

exactly on the transition point between two adjacent digital

output codes. This can be accomplished by connecting LED's

to the digital outputs and adjusting until certain LED's "flicker"

equally between on and off. Other approaches employ digital

comparators or microcontrollers to detect when the outputs

change from one code to the next.

For the ADS-929, offset adjusting is normally accomplished at

the point where the MSB is a 1 and all other output bits are 0's

and the LSB just changes from a 0 to a 1. This digital output

transition ideally occurs when the applied analog input is

+½ LSB (+305µV).

Gain adjusting is accomplished when all bits are 1's and the

LSB just changes from a 1 to a 0. This transition ideally occurs

when the analog input is at +full scale minus 1½ LSB's

(+4.999085V).

+15V

ZERO/

OFFSET

ADJUST

20kΩ

–15V

GAIN

ADJUST

SIGNAL

INPUT

50Ω

200kΩ

1.98kΩ

2kΩ

+15V

To Pin 20

of ADS-929

–15V

Figure 2. ADS-929 Calibration Circuit

Zero/Offset Adjust Procedure

1. Apply a train of pulses to the START CONVERT input

(pin 16) so the converter is continuously converting. If using

LED's on the outputs, a 200kHz conversion rate will reduce

flicker.

2. Apply +305µV to the ANALOG INPUT (pin 20).

3. Adjust the offset potentiometer until the output bits are

a 1 and all 0's and the LSB flickers between 0 and 1.

Gain Adjust Procedure

1. Apply +4.999085V to the ANALOG INPUT (pin 20).

2. Adjust the gain potentiometer until the output bits are all 1's

and the LSB flickers between 1 and 0.

Table 1. Zero and Gain Adjust

INPUT VOLTAGE

RANGE

±5V

ZERO ADJUST

+½ LSB

+305µV

GAIN ADJUST

+FS –1½ LSB

+4.999085V

Table 2. Output Coding

OUTPUT CODING INPUT RANGE

MSB

LSB

±5V

BIPOLAR

SCALE

11 1111 1111 1111

11 1000 0000 0000

11 0000 0000 0000

10 0000 0000 0000

01 0000 0000 0000

00 1000 0000 0000

00 0000 0000 0001

00 0000 0000 0000

+4.99939

+3.75000

+2.50000

0.00000

–2.50000

–3.75000

–4.99939

–5.00000

+FS –1 LSB

+3/4 FS

+1/2FS

0

–1/2FS

–3/4FS

–FS +1 LSB

–FS

Coding is offset binary; 1LSB = 610µV.

+5V

–12V/–15V

+12V/+15V

+

4.7µF

0.1µF

4.7µF

+

4.7µF

+

0.1µF

0.1µF

–5V to +5V

0.1µF

+

4.7µF

13

14

DIGITAL

GROUND

ADS-929

24

19, 23

ANALOG

GROUND

22

ANALOG

20 INPUT

21 +10V REF. OUT

START

CONVERT

16

18 BIT 1 (MSB)

17 BIT 2

12 BIT 3

11 BIT 4

10 BIT 5

9 BIT 6

8 BIT 7

7 BIT 8

6 BIT 9

5 BIT 10

4 BIT 11

3 BIT 12

2 BIT 13

1 BIT 14 (LSB)

15 EOC

Figure 3. Typical ADS-929 Connection Diagram

4

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