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SOLVED: My first TPS61175 Design... no gain...
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NivagSwerdna:
I've tried to build a .2A 35V supply using a TP61175 (see attached schematic) and not had any luck.

I've had to make a number of bodges... Pull Pin4 HIGH EN, and more significantly Pin 11 LOW... NC (and I thought NC would be No Connection!)
I connected the thermal pad to GND.

For some reason it just isn't oscillating... Any idea what I could try?
Audioguru:
I guess you did not read the datasheet. It says pin 4 must be high and pin 11 must be low. It also shows a Schottky diode (your schematic shows an ordinary diode) and ceramic input and output capacitors.
NivagSwerdna:

--- Quote from: Audioguru on June 09, 2019, 02:40:12 pm ---I guess you did not read the datasheet. It says pin 4 must be high and pin 11 must be low. It also shows a Schottky diode (your schematic shows an ordinary diode) and ceramic input and output capacitors.

--- End quote ---
I have Pin 4 High (was switched but now high) and Pin 11 Low (was Not Connected, bodged, per earlier schematic, to GND), My D1 is a B550C-13-F, which is "DIODE SCHOTTKY 50V 5A SMC";  C31 is 10uF EEHZA1H100R, C32   4.7uF   EEEFC1H4R7R.  I did add extra Capacitance at the input but no change.      

So my output caps are both Polymer Electrolytic... could that make a difference?  I'll go and read the datasheet again

Thanks for the interest
SiliconWizard:
I can't see anything clearly wrong with your setup. Could it be possible that powering the circuit while leaving the "NC" pin open could have fried the TPS61175 (before you figured it should be connected to GND?)
The datasheet states "Reserved pin. Must connect this pin to ground." I suspect it's some kind of test pin and have no clue what it does... Have you tried swapping the TPS61175 with a new one?
NivagSwerdna:

--- Quote from: SiliconWizard on June 09, 2019, 04:06:58 pm ---Have you tried swapping the TPS61175 with a new one?

--- End quote ---
I did swap with a TI Sample I had and same behaviour.  It's very odd.  I have ordered some 4.7uF ceramic as I don't have any of those to hand and will try again a few days.
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