The TI E2E™ design support forums will undergo maintenance from Sept. 28 to Oct. 2. If you need design support during this time, contact your TI representative or open a new support request with our customer support center.

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AMC7812: ADC gain register setting for differential input

Part Number: AMC7812

Hi Team,

Customer is going to use ADC CH0 and CH1 for differential input with full scale input range -Vref ~ Vref. I believe I should set bit 15 in ADC gain register for targeting operation. What about bit 14? Is it Don't care?

In addition, I'm a bit confused about full scale input voltage. When I set the FS range at -Vref ~ Vref, the voltage VDM = 2x (VDM/2) would be stored in ADC data register, and VDM should be between -2.5V and 2.5V. Is my understanding correct?

  • We will get an answer to you shortly.

  • Hi Paul,

    Please help update. Thank you.

  • Good afternoon, apologies for the delay in getting back to you as I was looking into your questions.

    1) With regards to the ADC gain register setting your understanding is correct in that bit 14 is don't care, but for a full scale range of -Vref to +Vref you must set bit 15 to 0 (i.e. bit 15 must be cleared). Please note that as per Table 23 in the datasheet (shown below) you also need to set bit 12 of ADC Channel Register 0 with all other bits set to 0 (if you only intend to use CH0 and CH1; else please refer to Table 24 for configuring CH2 and CH3).

    2) For a FS range of -Vref ~ Vref, VDM can be between 0 and 2.5 V. It will not be negative as each of the differential input voltages V1 and V2 can range from 0 to 2.5V, and VDM is a measure of the difference between these voltages (i.e V1 - V2 if V1 > V2, or V2 - V1 if V1 < V2). The value VDM is used to determine the magnitude stored in bits 0 through 14 of the ADC data register while the MSB (bit 15) will be set to 1 to indicate a negative value (if V2 is greater than V1) or set to 0 to indicate a positive value (if V1 is greater than V2).

  • Hi Anshuman,

    Thank you a lot for all details and clarification!