Unstable operation of the ADP7183 with a capacity of 1000 uF

Hi DmitriyDAK,

Apologies for the delay. Hope you found a solution to your problem already. It seems that this issue only happens on some chips but not the others? Make sure to get parts from authorized distributors only.

Hi, ron.p!

1. i buy chip from authorized distributors.

2. I've been getting similar behavior on different batches, on the ADP 7185 chip. It's the same everywhere. Therefore, I thought that someone could check on a demo sample from Analog device and say whether the behavior repeats or not.

3. I didn't find a chip in the brochure about limiting the maximum capacity. I found that the chip has an UNDERVOLTAGE LOCKOUT protection. I believe that this protection should work in my case, but I see an unregulated operation of the chip.

I also find information in Internet sources that LDO stabilizers do not like a large output capacity due to unstable start of the LDO in the presence of residual voltage on the output capacity of the LDO stabilizer. The reason lies in the numerous protection circuits of LDO stabilizers.

We suggest trying different output capacitors and see if the issue persists. The 1000uF output capacitor might be too large. In fact, this IC is designed to be stable at small output capacitors.

Hello.

1. If I reduce the capacity, the problem becomes harder to reproduce. The voltage at the output of the stabilizer drops to zero faster, then it is more difficult to get into an unfavorable moment of switching on.
2. The most important thing I want to convey is that the capacity does not affect the stability of the stabilizer when it is turned on normally. The capacitance value affects the subsequent switching processes if the voltage suddenly disappears. And this is very strange, because there is protection from this in the stabilizer, but it does not help.

Hi DmitriyDAK,

I guess it may have something to do with starting-up the LDO with a pre-charged output. This LDO is designed for small value of output capacitance for reduced size of overall solution so you don't need 1,000uF at output that is slowing down discharge of output voltage during turn-off that's causing issue. I'm not sure if LDO was tested at much larger output cap. I guess you have to change value of output capacitance.