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ADS131 power supply sequencing

Steve Hudson
Prodigy 140 points
Other Parts Discussed in Thread: ADS131E08

I am using the ADS131E08 using an analog supply voltage of +5V and a digital supply voltage of +3.3V. The negative analog power supply and digital grounds are tied to a common ground. On the first revision of my system, the 5V and 3.3V came up at the same time and the ADC operated with no problems. On the second revision of my system, the 3.3V powers on at the system start-up and the 5V supply is turned off to minimize power consumption of the analog system. The 5V supply is powered on much later when the operator is ready to take readings. However, the ADC will no longer communicate if the power supplies are sequenced in this order. I have tried resetting the ADC using the RESET pin, but it appears to have no effect. Please advise if the 3.3V and 5V must come on at the same time and if there are any other restrictions regarding power supply sequencing for this part.

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    TI__Mastermind 23235 points

    You may want to review the Power On Reset section of the datasheet.  We recently revised this section to better explain the requirements for the supply.  It may be that your RESET signal is not meeting the spec required to issue a clean RESET to the part.

    Can you just put the part in powerdown instead of removing AVDD?  The device has low power consumption in powerdown mode which may help your requirements.