LMH1297: Discharge of VDD_LDO Rail

Owen306

Part Number: LMH1297

I’m wondering if the capacitors connected to VDD_LDO will drain with the 2V5 rail if the 2V5 rail is connected to ground? I have a use case where I need to discharge all rails on our board and I’m wondering if I need a separate discharge FET connected to the LDO caps or if my discharge FET connected to the 2V5 rail will pull the charge from the LDO caps too? Thanks.

over 7 years ago

0 Nasser Mohammadi over 7 years ago

TI__Guru* 93570 points

Hi Owen,
LMH1297 has internal regulator that generates VDD_LDO. Output of this LDO is isolated from the main 2.5V supply. So eventually - when there is no 2.5V supply - it will drain through the supply coupling caps on VDD_LDO pin.
Regards,,nasser

0 Owen306 over 7 years ago in reply to Nasser Mohammadi

Prodigy 70 points

Thanks Nasser. I need the caps to discharge immediately so I've added a schottky diode between the VDD_LDO and 2.5V supply. When the supply drops out, the caps will drain via the diode.

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LMH1297: Discharge of VDD_LDO Rail