ADS-939 Просмотр технического описания (PDF) - Murata Power Solutions

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ADS-939

16-Bit, 10MHz Sampling A/D Converters

Murata Power Solutions 

ADS-939

16-Bit, 10MHz Sampling A/D Converters

CALIBRATION PROCEDURE

Connect the converter per Figure 2. Any offset/gain

calibration procedures should not be implemented until the

device is fully warmed up. To avoid interaction, adjust offset

before gain. The ranges of adjustment for the circuits in

Figure 2 are guaranteed to compensate for the ADS-939’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 is accomplished by connecting

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Figure 2. Connection Diagram

Table 2a. Setting Output Coding Selection (Pin 35)

OUTPUT FORMAT

PIN 35 LOGIC LEVEL

Complementary (Offset) Binary

1

(Offset) Binary

0

Complementary Two’s Complement

1

(Using MSB, pin 29)

Two’s Complement

0

(Using MSB, pin 29)

LED's to the digital outputs and performing adjustments 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-939, offset adjusting is normally accomplished

when the analog input is 0 minus ½ LSB (–42μV). See Table

2b for the proper bipolar output coding.

Gain adjusting is accomplished when the analog input

is at nominal full scale minus 1½ LSB's (+2.749874V or

–5.499874V).

Note: Connect pin 5 to ANALOG GROUND (pin 4) for

operation without zero/offset adjustment. Connect pin 6 to

pin 4 for operation without gain adjustment.

Zero/Offset Adjust Procedure

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

12) so that the converter is continuously converting.

2. For zero/offset adjust, apply –42μV to the ANALOG INPUT

(pin 3).

3. For bipolar operation - Adjust the offset potentiometer until

the code flickers between 1000 0000 0000 0000 and 0111

1111 1111 1111 with pin 35 tied high (complementary offset

binary) or between 0111 1111 1111 1111 and 1000 0000

0000 0000 with pin 35 tied low (offset binary).

For unipolar operation - Adjust the offset potentiometer until

all outputs are 1's and the LSB flickers between 0 and 1 with

pin 35 tied high (complementary binary) or until all outputs

are 0's and the LSB flickers between 0 and 1 with pin 35 tied

low (binary).

4. For bipolar, Two's complement coding requires using

BIT 1 (MSB) (pin 29). With pin 35 tied low, adjust the trimpot

until the output code flickers between all 0’s and all 1’s.

Gain Adjust Procedure

1. For gain adjust, for bipolar apply +2.749874V and for unipo-

lar mode 5.499874V to the ANALOG INPUT (pin 3).

2. Adjust the gain potentiometer until all output bits are 0’s and

the LSB flickers between a 1 and 0 with pin 35 tied high

(complementary (offset) binary) or until all output bits are 1’s

and the LSB flickers between a 1 and 0 with pin 35 tied low

((offset) binary).

3. For bipolar, Two's complement coding requires using

BIT 1 (MSB) (pin 29). With pin 35 tied low, adjust the gain

trimpot until the output code flickers equally between 0111

1111 1111 1111 and 0111 1111 1111 1110.

4. To confirm proper operation of the device, vary the applied

input voltage to obtain the output coding listed in Table 2b.

www.murata-ps.com

Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000

MDA_ADS-939.A01 Page 4 of 7

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