TINA/Spice/LM317MQ: drouput voltage in current liminting mode

Zsolt Gerlei

Part Number: LM317MQ
Other Parts Discussed in Thread: TINA-TI, LM317

Tool/software: TINA-TI or Spice Models

Hello,

I would like to calculate the dropout voltage (Vin-Vout) of the LM317, if it is in current limiting mode (only a resistor between Vout- ADJ). I did not find relevant information in the datasheet.

Thank you in advacne

Br,

Zsolt

over 6 years ago

0 David Hopkins over 6 years ago

TI__Expert 8905 points

Hi Zsolt,

The device itself needs at least 3V of headroom (Vin-Vout) for normal operation. After that add in the voltage drop due to the resistor so Vdo = 3V + Iout * Rout_adj

Regards,
David

0 Zsolt Gerlei over 6 years ago in reply to David Hopkins

Prodigy 20 points

Hi David,

Thank you, but based on simulation with Tina this voltage is around 500mV. 3V headroom is valid on LDO applocation , isn't it?

Regards,

Zsolt

0 David Hopkins over 6 years ago in reply to Zsolt Gerlei

TI__Expert 8905 points

Hi Zsolt,

The 3 V of headroom is still required for the LDO.

-David

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TINA/Spice/LM317MQ: drouput voltage in current liminting mode