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LTC3111 - VOUT to GND

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shawnmk123

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Hello,

I'm using the LTC3111. I have followed the typical application on page 1 of datasheet.
I'm operating in burst mode and no load current is drawn.

When I power up the IC, the output Vout (pin 12 of MSOP 16) goes to ground pretty quickly.
The only clues I have of what exactly is going on:
1. the O'scope probes are connected to FB, VCC, VIN and Vout. There is a lot of noise and spikes in the waveforms.
2. The current meter in my supply is showing 100mA-22mA-1mA depending on my voltage input.

Please help me understand why the IC is shorting internally.

Thank you,
 

KlausST

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Hi,

Your description is not very informative.
Especially the LT datasheets and descriptions - i find - are very reliable. So I rather think there is another problem.

Therefore we need YOUR circuit drawing with part names, values and pin nubers on the IC.
A picture of your circuit and a scope picture is often helpful.

****
for a first test measure folowing voltages (referenced to SGND pin of LTC3111)
* FB voltage of LT3111 (should be exactely and stable 0.8V, never higher than 0.8V)
* SNSGND of LT3111 (shoud be 0.00V)
* PGND of LT3111 (shoud be 0.00V)
* RUN pin LT3111 (shoud be more than 1.2V)

hope this helps

Klaus
 

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