Author Topic: Debugging LTC3612 Step-Down DC/DC Converter  (Read 467 times)

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Offline suppermanTopic starter

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Debugging LTC3612 Step-Down DC/DC Converter
« on: January 31, 2020, 12:06:02 am »
I'm not sure what I'm doing wrong. I suspect it may be related to the conductor I chose..

I have 3 similar circuits (see picture) that cascade when turned on to produce 3.3v, 2.5v and 1.2v to power an FPGA.
The 3.3v fires up ok.. and seems stable. Some noise.
The 3.3v PGood goes high and starts the 2.5V unit. (3.3v PGood is good.. never goes low after startup)
2.5V fires up.. and 2.5V Pgood goes high.. but then glitches low from time to time. unstable. (even at zero load)
2.5V out seems ok.. but does not hold up under load.

when I force 2.5v PGood high.. then 1.2V fires up. It has a stable PGood like the 3.3v
1.2v also can take a load.. but seems noisy when under load.

This is being tested on a PCB and each board seems to have the same issue - so it is not just a one off fault.

The fact that the 2.5v is the biggest problem in 3 similar designs.. it is very confusing to me.
Data Sheet of TLC3612: https://www.tme.com/Document/5d0c950d94ad7f073004a3fa8721e621/3612fa.pdf
Data Sheet of Inductor: https://www.mouser.com/datasheet/2/427/sc15ah01-105489.pdf

 


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