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LMR14020 Connection Question

Mathew Locoteta
Prodigy 200 points
Other Parts Discussed in Thread: LMR14020

Hi,

I'm fairly new to this and just need a bit of help.  

I bread boarded circuit as described by TI's web bench with substitutions from surface mount to through hole components w/ similar / same values. 

I got an output of 25VDC from a 36VDC input with the saw-tooth waveform as expected which I am fairly happy with. 

However, when I hook a load directly across the output terminals, this shorts the chip immediately.  For example, a small brushed DC motor (not the brightest idea) and the chip shorted and drew all available current. 

Then I replaced the chip, turned power off, hooked up a 24VDC low amperage photobeam (<20mA) and powered the circuit.  The photobeam lit and drew the correct amount of current. I disconnected the photobeam and reconnected it.  This killed the chip again.

So it seems that connecting something across the + and - while powered is my problem.  This is most likely a trivial problem but I am at a loss.

Any advice is appreciated.

Thank you,

Mat

  • 0
    TI__Genius 11085 points
    Bread board a circuit with 24W output power is not a good idea. The noise coupling, power dissipation and power density are all questionable. You could also have bad connections here and there. I'd recommend ordering a LMR14020 EVM from TI.com and modify the circuit for your need from there.