TPS51206: TPS51206 VTTREF capacitor and VDDQSNS question.

Hi,

It's ok to use 2.3uF for VTTREF.

Regarding VDDQSNS, this is an input pin so it really depend on the VDDQ range. Usually it's 1.2V +60mV/-40mV for DDR4.

Regards,
Weidong

Dear Weidong Zhu,

Thank you very much for reply.

I reply my customer your answer.

Best regard.

Bob Lee.

Dear Weidong Zhu,

I have a question.

I mistaked about VTTREF capacitor.
VTTREF capacitor is designing 13.3μF.

Q1.
I designe load capacitance of 13.3 uF is connected,Is there a problem?

Q2.
Since the VTTREF output is generated by the Voltage follower operational amplifier,
does VTTREF capacitor oscillate because it is too large?

Best regard.
Bob Lee.

Hi Bob,

13.3uF is too large. Ideally we should keep the VTTREF decoupling cap under 1uF but 2.3uF should still be ok. If it's 13.3uF it's way over and could cause stability problem.

Do you have the waveform of the oscillation and can you see if it can be improved by reducing the capacitance.

Regards,
Weidong