LM5121-Q1: NO WAVEFORMS AT HI-LO PINS

makarand parkhi

Part Number: LM5121-Q1
Other Parts Discussed in Thread: LM5121

FIND ATTACHED MY CIRCUIT USING LM5121. & LAYUT FOR BOSSTING VOLTAGE FROM 48VDC TO 60VDC.BOOST_CONTROLLER_LAYOUT.pdf BOOST_CONTROLLER_POWERTEK.pdf

THE PROBLEM WITH IT IS , THE PINS HI & LO DONOT SHOW ANY WAVE FORMS EVEN INPUT LO PIN IS AT 1.4V & INPUT VOLTAGE IS AT 40VDC.

CAN ANY ONE CHECK CIRCUIT AND TELL IF ANY THING IS WRONG IN IT?

over 7 years ago

0 Youhao Xi over 7 years ago

TI__Guru* 78060 points

Your diodes D2 and D5 are in the wrong polarity, not allowing the Vgs to be established to turn on the FETs. By the way, your schematic does not show the ground connection from Q3 source to GND. However, the PCB seems having the connection.

0 makarand parkhi over 7 years ago in reply to Youhao Xi

Prodigy 20 points

d2 & d5 are zener, by oversight shown as 1n4007.

0 Youhao Xi over 7 years ago in reply to makarand parkhi

TI__Guru* 78060 points

They are used in the wrong polarity. Not sure why they are needed there. Please delete them, or flip them if you still want to keep them on board. Then you should see normal gate drive voltages.

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LM5121-Q1: NO WAVEFORMS AT HI-LO PINS