ADS-947GE 查看數據表（PDF） - Murata Power Solutions

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ADS-947GE

14-Bit, 10MHz Sampling A/D Converters

Murata Power Solutions 

ADS-947

®

®

CALIBRATION PROCEDURE

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 circuits in Figures 2 and 3 are guaranteed to

compensate for the ADS-947’s initial accuracy errors and may

not be able to compensate for additional system errors.

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.

Offset adjusting for the ADS-947 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 (+122µV).

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

(+1.99963V).

Zero/Offset Adjust Procedure

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

18) so the converter is continuously converting.

2. Apply +122µV to the ANALOG INPUT (pin 21).

3. Adjust the offset potentiometer until the output bits are

10 0000 0000 0000 and the LSB flickers between 0 and 1.

Gain Adjust Procedure

1. Apply +1.99963V to the ANALOG INPUT (pin 21).

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

the LSB flickers between 1 and 0.

3. To confirm proper operation of the device, vary the input

signal to obtain the output coding listed in Table 2.

Table 1. Gain and Zero Adjust

INPUT VOLTAGE

RANGE

±2V

ZERO ADJUST

+½ LSB

+122µV

GAIN ADJUST

+FS –1½ LSB

+1.99963V

Table 2. Output Coding for Bipolar Operation

BIPOLAR

SCALE

+FS –1 LSB

+3/4 FS

+1/2 FS

0

–1/2 FS

–3/4 FS

–FS +1 LSB

–FS

INPUT VOLTAGE

(±2V RANGE)

+1.99976

+1.50000

+1.00000

0.00000

–1.00000

–1.50000

–1.99976

–2.00000

OFFSET BINARY

MSB

LSB

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

–5.2V

+5V ➀

4.7µF

+

4.7µF 4.7µF

++

0.1µF

0.1µF 0.1µF

19

ANALOG

INPUT

21

+5V

ZERO/

OFFSET

ADJUST

23

20kW

–5V

START

CONVERT

18

20

24 22, 13 14

ADS-947

1 BIT 1 (MSB)

2 BIT 2

3 BIT 3

4 BIT 4

5 BIT 5

6 BIT 6

7 BIT 7

8 BIT 8

9 BIT 9

10 BIT 10

11 BIT 11

12 BIT 12

15 BIT 13

16 BIT 14 (LSB)

17 DATA VALID

➀ A single +5V supply should be used for both the +5V analog and +5V digital.

If separate supplies are used, the difference between the two cannot exceed 100mV.

Figure 3. Typical ADS-947 Connection Diagram

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