ADS-119MC 查看數據表（PDF） - Murata Power Solutions

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ADS-119MC

12-Bit, 10MHz, Low-Power Sampling A/D Converters

Murata Power Solutions 

ADS-119

®

®

CALIBRATION PROCEDURE

(Refer to Figures 3 and 4, Table 1)

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 Figure 3 and 4 are guaranteed to

compensate for the ADS-119'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-119 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 (+366µV).

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 1 ½ LSB's

(+1.4989V).

Zero/Offset Adjust Procedure

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

(pin 16) so the converter is continuously converting.

2. Apply +366µV to the ANALOG INPUT (pin 19).

3. Adjust the offset potentiometer until the output bits are

1000 0000 0000 and the LSB flickers between 0 and 1.

Gain Adjust Procedure

1. Apply +1.4989V to the ANALOG INPUT (pin 19).

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 1.

Table 1. Output Coding for Bipolar Operation

BIPOLAR

SCALE

ADS-119

INPUT VOLTAGE

(±1.5V RANGE)

OUTPUT CODING

OFFSET BINARY

MSB

LSB

+FS–1 LSB

+3/4 FS

+1/2 FS

0

–1/2 FS

–3/4 FS

–FS +1 LSB

–FS

+1.49927V

+1.12500V

+0.75000V

0.00000V

–0.75000V

–1.12500V

–1.49927V

–1.50000V

1111 1111 1111

1110 0000 0000

1100 0000 0000

1000 0000 0000

0100 0000 0000

0010 0000 0000

0000 0000 0001

0000 0000 0000

GAIN

ADJUST

SIGNAL

INPUT

50Ω

1.98kΩ

2kΩ

+15V

To Pin 19

of ADS-119

–15V

Figure 3. Optional Calibration Circuit, ADS-119

+5V Œ

4.7µF

0.1µF

13, 20

14

–5V

4.7µF

0.1µF

+5V

20

18, 20

OFFSET

ADJUST

17

20kΩ

–5V

ADS-119

12 BIT 1 (MSB)

11 BIT 2

10 BIT 3

9 BIT 4

8 BIT 5

7 BIT 6

6 BIT 7

5 BIT 8

4 BIT 9

3 BIT 10

2 BIT 11

1 BIT 12 (LSB)

15 DATA VALID

19 ANALOG INPUT

16 START CONVERT

ΠA 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 4. Typical Connection Diagram

4

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