TPS62111: TPS62111RSAR Ripple

Koteswar,

Can I see your ripple waveform and schematic?

Hi John Please find the Schematics and wave form

Working on light load, less than 10mA. typically 6mA

Input voltage is 6.7V and output is 3.3V

the ripple RMS requirement is less than 2.2mVrms.

Koteswar,

What are each of the channels in your waveform?  2.2 mV is a very low ripple requirement.  You will not meet that without a secondary filter or LDO follower.  Typically around 7 mV p-p is the best you can do with an ordinary buck converter.  What is your timeframe?  We do have a new product releasing soon that may work well for you.

Hi John,

The problem is with the Ripple at Vin pin not at the output pin.

How can we reduce the input pin ripple which is causing problems at the 4-20mA loop and ripple frequency(5-10KHz) level is a problem.

Can we increase the Burst frequency above 10KHz without changing load, if so what changes to be made.

Koteswar,

I do not see any input capacitors on the VIN pins.   You will need 10 uF ceramic at a minimum.  If you need very low input ripple more will be required.  Possibly an additional LC filter as well.

Yes John the 10uF is there in the other page but placed near to the Vin pin in the layout.

In one of your conversation you said new parts are coming up. can you please suggest for our application

Vin is 6V - 8V

Vout is 3.3V

Iout Max is not more than 20mA

Vin/Vout ripple is less than 2mV RMS

Inductor value shall not more than 10uH

Hi john,

One more clarification in PFM mode can we change the switching frequency/Burst Frequency.

if so how to do it.

What is the function of Sync pin function in PFM mode