LM5121: LM5121 Inrush Current Limit Programming#2

watchaphong Aoopree

Part Number: LM5121

Now I use LM5121 for boost input from 10.5V - 14.5V to output 24V Power 200W and i set OCP Point by RSENSE Current = 3mohm.

but i found gate drive dissconnect switch input MOSFET cannot turn off. when converter shut down OCP affect to input voltage bypass to output.
and i have improved this issue by add Inrush Current Limit Programming #2 (R_Inrush = 10Kohm). I have some question about this circuit as below.

1. Resistor bias transistor is RSLOPE? (Original i use RSLOPE = 100Kohm connect to GND @ freq 150KHz ).

2. How to calculate Resistor bias transistor?

Best regards

Watchaphong

over 6 years ago

0 Jasper Li over 6 years ago

TI__Mastermind 46905 points

Hi Watchaphong
the engineer supporting this device is out of office now. He will reply you next week.

0 Youhao Xi over 6 years ago in reply to Jasper Li

TI__Guru* 78270 points

Hi Watchaphong,
Please share your entire schematic. In shutdown the Lm5121 should turn off the disconnect switch. What you did may help you but these external components may not be necessary.

Thanks,
Youhao Xi, Applications Engineering

0 watchaphong Aoopree over 6 years ago in reply to Youhao Xi

Prodigy 30 points

0 Youhao Xi over 6 years ago in reply to watchaphong Aoopree

TI__Guru* 78270 points

Sorry this is not the complete circuit. What to you meant by "when converter shut down ..." I don't see your means of shutdown except for the VIN drop that trips UVLO. Did you mean that?

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LM5121: LM5121 Inrush Current Limit Programming#2