UCD3138A: UCD3138ARMHR adc sampling error

user4357894

Part Number: UCD3138A

Dear TI,

We found a UCD3138ARMHR failed to accurate adc sampling.The fail IC can not correctly read the ADC input voltage when the adc voltage below 1V.

Test condiction : the DC Source value directly connect to adc,and we read ADC value in register.

The tabel bellow is ADC test data result : the voltage input and read are not same.

Can you explain it, is the chip had broken?

Best Wishes

LEI

0 user4357894 over 8 years ago

The table :
ADC input voltage (V) ADC read value(V)
0.06 0.0048
0.1 0.046
0.2 0.15
0.3 0.25
0.4 0.36
0.5 0.46
0.6 0.57
0.8 0.78
0.9 0.89
0.95 0.94

0 Ian Bower over 8 years ago in reply to user4357894

There are two likely issues:

1. Noise

2. Source impedance. If your source is over 1K ohms, you will start to get noise from the ADC sampling.

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