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TPS40425: TPS40425 default Two Phase Operation

Part Number: TPS40425
Other Parts Discussed in Thread: TPS40428


I have designed TPS40425 for two-phase operation after most of the work is done, I have realized the default mode is dual output.

Unfortunately, my design doesn't have PMBus. It takes a lot of time to find a new device and design.

Could you please suggest any quick change?

Thanks in advance.



  • There is a similar question on e2e here. The device can be used in 2 phase mode, with the default settings. The Phase number programming in MFR_22 is needed for multi-controller operation (3+1 and 4+0 operation). 

    But, please do check the default value of IOUT_CAL_GAIN, which does need to be matching your inductor DCR. You may be better off using TPS40428 + smart power stage, instead of TPS40425+DCR sensing with the default settings, since the smart powerstages have a fixed current sense gain of 5mOhm.

  • Hello Matt,

    Thanks for the reply.

    I had gone through the post in e2e, and checked TPS40428 as well. Both datasheets have the same description for MFR_SPECIFIC_22.

    Please see below. Default: 00b, which is a dual-channel operation.

    Please let me know if my understanding is wrong.



  • Pulling the FB2 pin to BP5 is what actually puts the 2nd channel into a loop slave mode. 

    The programming in MFR_22 is used to set the oscillator frequency higher for 3-phase mode, and enable 90deg/120deg phase shifts in 4 phase mode. For a 2ph design, either 1+1 or 2+0, you'll get 1x frequency and 180 degree phase shift. This setting is needed more for multi-controller operation. 

  • Hello Matt,

    Thanks for the confirmation.