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TPS56637: 2 Questions for TPS56637 (Power On and max input voltage)

Seokmin Hong
Intellectual 485 points
Part Number: TPS56637

Hi, I am  going to use TPS56637 for my system.

I have two questions using TPS56637.

--------------------

Question 1.

To enable TPS56637, in the datasheet 
"Driving EN high or leaving this pin floating enables the converter."

I want to make auto enable TPS56637 when Vin ramps up. 

Which way would you recommend for this? Are both way have same internal soft start time? (Tss for 2ms?)

1. Using two resistors for voltage divide from VIN to make EN high.

2. or Just floating?

-------------------------------------

Question 2.

TPS56637's absolute maximum of VIN voltage is 32V.

and operating max VIN voltage is 28V.

-----------------------------------------------------------------------------

I am going to use 7s Li-Ion battery for this system. This will make max VIN voltage 29.4V.

Because there is Over voltage protection in Battery, so the battery will never go up above 29.4V.

In this case, can I use TPS56637 for this system? (About 1.4V will over when I use TPS56637 in my system )

Thanks.

  • 0
    TI__Expert 5030 points

    Hi 

    1. Both ways are OK. The soft start will begin when Vin>wake up Vin voltage and VEN>VENon (enable threshold).

    2. In my point of view, TPS56637 isn't recommended to use for this system. Since the abs maximum SW voltage in transient is about 32.5V, that means if the ring on SW is above 3.1V, there's risk to damage the device. It's hard to ensure and that has very high requirements for the PCB layout.

    Regards,

    Andrew