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ADM1064 glitching on power up

Question asked by ianstedman on Jan 30, 2015
Latest reply on Apr 27, 2015 by ianstedman

Hi,

 

I have a design that uses the ADM1064 super-sequencer device. Whilst tracing a fault with another device, I observed that two of the power supplies, controlled by the ADM1064 were glitching on power-up. I believe this is due to the ADM1064 experiencing a brown-out condition.

 

The card I was investigating is one of two PCBS in a module. The baseboard has a competitors power monitor, that switches +5V and +3V3 through power MOSFETs to the onboard circuitry. When it switches the supplies through, in a staggered mode, the large capacitance causes the +5V and the +3.3V supplies to dip. This causes the ADM1064 to dropout and re-start twice.

 

Comparing my design to the evaluation board I can see a difference. The VCCP, REFOUT and VDDCAP capacitors on your design are AVX TAJB Tantalum capacitors. On my design they are Kemet X7R ceramics. Can the internal LDO converter connected to the VDDCAP cope with a ceramic capacitor on it's output?

 

Regards,

 

Ian

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