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TPS65381A-Q1: Monitor ext. 3V3 Rail

Basil
Intellectual 1620 points
Part Number: TPS65381A-Q1
Other Parts Discussed in Thread: TPS62160, TPS3700-Q1

Dear Team,

could you please support with following question:

In our system we use the TPS65381A-Q1 with VDD3/5=3.3V.

Because we need more current than VDD3/5 can source, we are using a separate DC/DC buck TPS62160.

Is it possible to connect the two 3.3V rails together in order for both to be monitored by TPS65381A-Q1, like you suggested here for VDD1: https://e2e.ti.com/support/power_management/pmu/f/200/t/607288?tisearch=e2e-sitesearch&keymatch=TPS65381

Thanks and best regards,

B

  • 0
    TI__Mastermind 20590 points
    Hi Basil,

    It is not possible to connect two power supplies together like this to gain monitoring from VDD3/5 for an external DC/DC. However if you are not using VDD1 regulator you may use the VDD1_SENSE feedback/monitoring pin in this fashion by re-using the VDD1 monitoring and not populating the gate drive/FET. Another option is to use the VSOUT1 feedback/monitoring if you are not using the VSOUT1 regulator by using the VSFB1 pin to monitor the DC/DC. In both cases you would need to resistor divide the 3.3V down to the target feedback / comparator voltage for that specific feedback/monitor pin. The comparator sense voltage for VDD1_SENSE outlined with datasheet electrical characteristic POS 4.2, VDD1SENSE = 0.8V (0.792V minimum, 0.808V maximum) and VSFB1 has POS 5.3 VSFB1 = 2.5 V (2.45V minimum, 2.55V maximum).

    If you are using all the rails on the device you will need to use an external monitor something like: TPS3700-Q1.

    Please let us know if you have further questions.

    Best Regards,
    Scott