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  • TI Thinks Resolved

LM5117: LM5117 lock issue

Intellectual 820 points

Replies: 2

Views: 89

Part Number: LM5117

Hi there,

Could you please help our customer‘s questions as below?

Please find the LM5117 quick start file and schematic attached. VCC is powered by external 12V/300mA DCDC. Please help review whether it’s ok.

 A new LM5117 can output 12V/10A, but when they sink 12V/9A+ for several minutes, then LM5117 Vout will decrease to ~7.4V (empty load), and can’t stand any load, IC heat up, IC consumption 184mA /45Vin. Some failure units VCC drains from 12V to <10V, then IC can recover if supply a 12V/1A power source to VCC pin to enforce VCC to 12V. Customer thinks this is LM5117 “LOCK up” issue.

Customer has tried MOSFET TK100E10N1 and HGP(B)080N10AL (lower Qg=32nC /Ciss=1876pF0 ), and issue still exists.

We don’t see any “LOCK” mode in LM5117 datasheet, but I think it might be caused by some component drains too much current, causing VCC collapse. CSD19533Q5A is not effective to test now due to different package.

It seems IC is in Diode Emulation Mode when it’s “LOCK”, low side FET is off, high side FET very short duty cycle. Could you confirm?

  lm(2)5117_quick_start_lv_calculatorV1.5.xls

  • I am  not able to find your attached schematic.

    Can you please send both your schematic and an image of your PCB layout.

    Thanks

  • In reply to Frank De Stasi:

    I am closing this due to inactivity.

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