TPS51216: About the value VDDQ output capacitor from REFIN to GND

Hi Sho,

If the large value capacitance is placed between REFIN and GND, the REFIN will rise up slowly during power on.

That means the VDDQ startup time will be longer.

Other than that, 0.22uF should be fine during normal operation.

Thanks

Qian

One limitation of REFIN capacitor is the REFIN voltage needs to reach the target value before PGOOD comparator enabled.

The below informaiton is capture from datasheet page 15.

Hi Qian san

Thank you for your reply.
I understood about capacitor value.

I have one more question about overvoltage protection.
TPS51216 and TPS51219 are similer devices.
These device set overvoltage protection when the VDDQSNS voltage reach a level 20% higher than REFIN voltage.
My customer confirmed the this condition with TPS51219 when the device is starting up, and output voltage of this device droped to 0V.
When softstart was completed, the VDDQ voltage jumped up(spike or overshoot) and the voltage became 20% or more higher than VREFIN.

I don't know why the VDDQ voltage jumped up(spike or overshoot).
Do you have a such case? If you have it, please tell me the ditail reason.
My customer concern that the VDDQ voltage will jumped up with TPS51216.

I got the customer ciurcuit, but this cuircuit information is confidential.
So if you need the circuit, please give me the mail.
e-mail : ogane-s@clv.macnica.co.jp

Best Regards,
Sho

I will contact you by email.

Thanks

Qian