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DC / DC circuit not producing any output - TPS562200, TPS563200, TPS54332

Thomas Phan
Intellectual 785 points
Other Parts Discussed in Thread: TPS562200, TPS563200, TPS54332

Hello,

My group and I are working on a project, and we're having a problem trying to read outputs from our DC/DC converter circuit. We're using 3 different TPS converters as listed in the "Subject" (TPS562200, TPS563200, TPS54332) to get the 3 different voltages that we need. But right now when we provide a power source of around 10-14V from a battery, we're not getting any voltage for the output. We're expecting to receive voltages of 3.3V, 5V, and 12V. I included here the schematic of our DC/DC circuit, and was wondering if someone could help take a look at it and see if there's anything wrong, know why we're not receiving any output. or have suggestions on what we can do to test the circuit. Thanks!

- General Overview

- Supply 1 (5V)

- Supply 2 (3.3V)

- Supply 3 (12V)

  • 0
    TI__Guru**** 191445 points

    TPS563200 and TPS562200 are pretty simple.  I do not see anything wrong with the schematics.  The TPS54332 compensation components look suspect.  Also, I usually like to design with a little more output capacitance than 2 x 10 uF.  For 12 V output you may need as high as 14.1 V input voltage.

    First thing is to check your build for errors.  Did you follow all the layout guidelines?  If you have a good input voltage at the VIN pins, then check the switching nodes.  Each should have a pulse waveform from slightly below GND to VIN at a duty cycle roughly VOUT/VIN when loaded.  With no load, they will be in puls skipping eco-mode, but you should still have a regulated output.

  • 0 in reply to JohnTucker
    Intellectual 785 points

    Hi John,

    I'll keep the capacitance tip in mind. This design came from WeBench, so we were a little surprised that it wasn't working. Someone else told us that we were supplying the TPS EN pin with 12V when it was supposed to only be around I think 1.5 according to the datasheet? Would changing this do anything? We found out that the chip was short-circuited on the inside and we suspect that it might be because were were supplying the EN pin with too much voltage/current.

    Thomas

  • 0 in reply to Thomas Phan
    TI__Guru**** 191445 points
    For TPS56X200, EN abs max is VIN, so no issues there for your TPS54332, you are using the internal UVLO, so that also should not be a problem so lang as your input voltage is rising at a faster rate than SS.

    Webench does like to pick low output capacitance to keep size and BOM cost low. Switching converter design has a little bit of "art" to it as well as pure science. Hard to program that into software.

    Did you check your waveforms? How about the layout?