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LM5642 BUCK CONVERTER NOT WORK

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SILVESTROS13:
Hello to all !
getting some info from AN1292 (Texas application for LM5642 ),I made  dc-dc converter to use at a solar controller. At test with no load the converter not work . no output, no pulses 200khz to drive mosfets. it seems to be disable ( on/ss pins below 2volts ). I was checked  hardware for errors many times , but I don't find something. The measurements shows that ic is ok , but something disable output.   Any idea for possible reasons ?   

Xenoamor:
Does it operate with a load?

SILVESTROS13:
Xenoamor,
no, the converter works as voltage regulator with feedback control. So, there is no need load to set the output voltage. The converter remains in disable mode for some reason that I try to find.

deskpro256:

--- Quote ---
From TI LM5642 datasheet http://www.ti.com/lit/ds/symlink/lm5642.pdf:
ON/SS1 Channel 1 enable pin. This pin is internally pulled up to one diode drop above VLIN5(Basically its on by default). Pulling this pin below 1.2V (Pin 9)
(open-collector type) turns off Channel 1. If both ON/SS1 and ON/SS2 pins are pulled below 1.2V, the whole chip
goes into shut down mode. Adding a capacitor to this pin provides a soft-start feature that minimizes inrush
current and output voltage overshoot
--- End quote ---

If I understand correctly, the SS1 and SS2 pins need to be HIGH for the outputs to work. According to your measurements, those pins are below 1.2V, hence the chip is in shudown mode.

Others? Does that seem right?

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