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TPS54061-Q1 under voltage condition vin < vout

Alexander Schaeder
Prodigy 415 points
Other Parts Discussed in Thread: TPS54061-Q1

Gents,

         I would like to design a wide Vin application using TPS54061-Q1 for an automotive application running from a 24V battery. Here are the design parameter.

Primary Regulator TPS54061-Q1:

  • Vin-max = 60 V
  • Vin-min = 8.5V
  • Vout = 12 V
  • Iout = 0.15A
  • In case of Vin < Vout we expect to see that Vin roughly follows Vout and the regulator stays stable under this condition. This is important in case a cascaded LDO  generates a 5V from  Vout (12V) rail
  • UVLO as low as possible

Can you please comment these  requirement with focus on the  Vin < Vout topic. We expect to see that Vin roughly follows Vout and the regulator stays stable under this condition down to 8.5V

I also appreciate your recommendation with regards to

-          Highest Switching frequency and still meeting minimum  on-time with an adequate margin since on time is shown as typical value

-          resistor values at the Enable pin for wide Vin operation from 60V  down to 8.5V 

Thanks & Regards,

Alexander

  • 0
    TI__Mastermind 35115 points

    Hi Alexander,

    The TPS54061-Q1 will work as expected in the case of Vin<Vout. Since the TPS54061-Q1 is synchronous it has a low-side MOSFET which will switch on to keep the BOOT capacitor charged. Depending on the load you may see some small ripple on the output when the low-side MOSFET turns on to recharge the BOOT capacitor.

    For the switching frequency, I need to do some more checking for the maximum minimum on-time. What switching frequency are they trying to operate at?

    For the EN pin, they will likely need to add an external zener to clamp the max EN voltage within the maximum ratings. I'm also checking into this.

    Best Regards,
    Anthony

  • 0 in reply to Anthony F
    TI__Mastermind 35115 points

    Based on our characterization data across the TPS54061-Q1 operating TJ range, when choosing the maximum switching frequency I recommend using 160 ns as the maximum minimum on-time.