Sync Pin of TPS40400

Soo,

I think you should connect the sync pin to GND. SYNC pin is an input pin with high impedance. Noise or leakage current can cause the pin to glitch if left floating.

Regards,

Na

Hi Na,

You mean output voltage could be unstable like oscillation or the IC could be damaged if the sync pin leave open?

Could you please explain detail about  what would happen if sync pin of TPS40400 is floating?

Thanks.

Hi Soo,

I mean the output voltage could be unstable. Not IC damage.

Regards,

Na

Na,

I am testing POL used TPS40400(opened sync pin mistakenly) at some environment condition such as 85% humidity test.

I saw output voltage hiccping during this test but not sure what caused the unstable so far.

Do you think the undatble relates to sync pin opened and may go even worse at humidity(85%) condition?

Thanks.

Hi Soo,

It's hard to draw the conclusion. I think there are more investigation should be done.

If we suspect the sync pin, you may connected SYNC pin to ground through a 10kohm resistor like in the EVM and check whether there is still instability issue.

You may also want to check whether the control loop is stable. The loop design file is available on the TPS40400 webpage. I also attached here for your reference.

0218.sluc263d.zip

Regards,

Na

Na,

I contacted local FAE, he said SYNC pin should be grounded so we are testing now as he said.

I will let you know the result, thanks.