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TPS40425: Can I design a DCDC base on TPS40425 without PMBUS control

roger zeng
Prodigy 230 points
Part Number: TPS40425
Other Parts Discussed in Thread: TPS40428

hello guys:

Now I have selected TPS40425 for a 12V input and 1V@50A output DCDC in 2 phase working mode, I have some issues can not find answer:

1: If I don't use the PMBUS to feed any parameters to the device, Does the device can also working with the default parameters, If yes I have a other question shown below;

2: I want to control the TPS40425 with CNTL1 and CNTL2, I have find the description in datasheet CNTL1 and CNTL2 accept logic level input to start or stop the channel

    in 2 phase working mode use CNTL1 to control and CNTL2 let float, But I have not find the CNTL sequence time wave in datasheet, if let the device use the default parameters how can I turn it on or turn it off with a logic level high(1) or low (0) 

3: There are two pcs power stage working with the TPS40425 in my design, But the power stage also has it's own EN signal, Can I use this signal to enable or disable the output of the power?? Generally designer often let the power stage in enable state. which control strategy is recommended ???

  • 0
    TI__Mastermind 24075 points

    Hi Roger, 

    1. The PMBus register IOUT_CAL_GAIN value should be equal to inductor DCR, otherwise OC threshold will not be accurate. The default OC threshold is 30A (inductor peak current) per phase, which is too low for 2phase 50A design. 

    2. Yes. In default the rail is turned on and off by CNTL1 and CNTL2. In 2phase mode, both channels are controlled by CNTL1 only. 

    3. I suggest to short power stage EN pin to power stage VDD pin. 

    If you want to use PMBus default setting, I suggest to use TPS40428+CSD95378B, so you don't need to program IOUT_CAL_GAIN and OC threshold. OC threshold is 40A per phase in TPS40428 which is good for 2phase 50A design. 

    Thanks

    Qian