AMC7836: POWER SEQUENCE

Hi David,

1. Section 9 in the AMC7836 datasheet describes the recommended sequence. I think the customers solution is acceptable, and we even comment on the conditions that may arise when AVEE is supplied first:

"The preferred (not required) pin order for applying power is IOVDD, DVDD and AVDD, AVCC and lastly AVEE, AVSSB, AVSSC, and AVSSD. When power sequencing, ensure that all digital pins are not powered or in an active state while the IOVDD pin ramps. Proper sequencing of the digital pins can be accomplished by attaching 10-kΩ pullup resistors to the IOVDD pin, or pulldown resistors to the DGND pin. See the supply voltage ranges in the Recommended Operating Conditions table.

In applications where a negative voltage is applied to AVEE, AVSSB, AVSSC, and AVSSD first, the user may notice some small negative voltages at other supply pins, such as the AVDD, DVDD, and AVCC pins. The negative voltages at the supply pins may exceed the values listed in the Absolute Maximum Ratings table, but because these voltages are created from intrinsic circuitry, the voltage levels are safe for operation. Although these
negative voltages are observed on the pins, the user must still adhere to the guidelines specified in the the Absolute Maximum Ratings table and verify that the inputs are driven within the range specified in the table. The user should also ensure that current is only applied when operating with voltages between the ranges listed in the Absolute Maximum Ratings table. "

2. The bipolar ADC inputs can accept up to ±12.5V with an acceptable AVDD voltage. So you should be able read the 6V input without issue.

Thanks!
Please let me know if this answered your questions.

Paul