MP2979A Provide wrong reading for output current

DC-DC Power Converters
1

Hi,

I am using MP2979A IMVP controller in my design along with MP86945-AGVT-Z power driver.
I have two queries-

  1. By-default it is in PFM/PSM or in PWM mode? If PWM then how to set in auto mode where it can switch from PSM to PWM or vice-versa according to load.

2. Whenever i am reading 97h register it is giving 0 value but for 96h register it is providing some numbers. How is it possible? do we need correct firmware to load to read those register properly. For me current number 8Ch is also varying from 3A to 7A when system is in idle condition.

MP2979A
MP2979A1462×879 153 KB

Thanks

Sagar

2

Hello Sagar,

Apologies for the delayed response here. To address your questions in the order asked:

  1. The MP2979A controller should be running full-phase PWM mode by default. See register MFR_PFM_SET (CFh) to enable the detection for when the switch frequency of your rails.
  2. Register 96h is Rail B’s power output reading for the lower 9 bits of this register. Register 97h is the total input power for the lower 9 bits. From your schematic, it looks like you are using two rails. It is hard to see, but is it possible that you are using only rails A and C?

Since it has been some time, please let us know if there have been any developments and updates here.