TPS63020 Vout deviation in power save mode

Q: TPS63020 Vout deviation in power save mode by 1433869

Hi:

Sorry need you guys help.

1. Could you provide Vout’s deviation in power save mode?

2. Do you have formula about estimating Vout range in power save mode?

3. Why Vout in save mode is a little higher than PWM mode's?

please see sheet2

2061.tps63020 issue.xls

thanks

 

A: Re: TPS63020 Vout deviation in power save mode by 1129650

Though we don't have a formula for estimating Vout range in power save mode (PFM), I recommend designing for significant margin using 25mV as the range on Vfb for PFM. 


A: Re: TPS63020 Vout deviation in power save mode by 1129650

The TPS6302x is expected to have a higher output voltage in power save (PFM) mode. 

This prevents the output voltage from dipping below the set output when a load is applied. 

In PFM mode, the feedback is between two points near  .500V and .525V  which is why the average output is measured at .512.

I have measured this on an evaluation module with no load to demonstrate. The results are visible in the following scope shot:

 


A: Re: TPS63020 Vout deviation in power save mode by 1129650

The other possibility is to operate in fixed PWM mode to reduce the output ripple . This will however decrease your efficiency at loads less than approx. 100mA.