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Power Up Sensitivity in Time of AD7376

Question asked by jkellar on Oct 3, 2013
Latest reply on Oct 4, 2013 by DRice

I'm reading the datasheet for the AD7376 and it says the following:


Because of the ESD protection diodes that limit the voltage compliance at Terminals A, B, and W (see Figure 30), it is important to power VDD/VSS before applying voltage to Terminals A, B, and W. Otherwise, the diodes are forward biased such that VDD/VSS are powered unintentionally and affect the system. Similarly, VDD/VSS should be powered down last. The ideal power-up sequence is in the following order: GND, VDD, VSS, digital inputs, and VA/VB/VW. The order of powering VA, VB, VW, and the digital inputs is not important, as long as they are powered after VDD/VSS.


So exactly how sensitive is this VDD and VSS to VA, VB and VW in time? We have a system that we'd like to add this device to and power all comes up together. The AD7376 would be a feedback pot on a non-inverting amplifier. I'm thinking its probably a non-issue since the op-amp and AD7376 will get power at the same time and the output from the op-amp will trail the supply coming up. Just would like a good feel for how much time lag should VA, VB and VW allow for VDD and VSS.