LMR38025-Q1: Enable input leakage current

Gilberto Ermacovitch

Part Number: LMR38025-Q1

I need to design a circuit to control an LMR38025SQDRRRQ1 via the EN pin.

The best option would be a pull-up resistor and a transistor in the open-collector configuration.

Could you tell me the maximum resistor value for a voltage of 20V?

BR
Gilberto

13 days ago

0 Tony Koulong 13 days ago

TI__Intellectual 1670 points

Hi Gilberto,

Is 20V your turn on voltage?

0 Gilberto Ermacovitch 12 days ago

Prodigy 225 points

20V is the maximum operating voltage.

BR
Gilberto

0 Tony Koulong 12 days ago in reply to Gilberto Ermacovitch

TI__Intellectual 1670 points

Is that the input, output or turn on voltage?

0 Gilberto Ermacovitch 9 days ago in reply to Tony Koulong

Prodigy 225 points

20V is the input voltage. The output is 5.0V.

0 Tony Koulong 8 days ago in reply to Gilberto Ermacovitch

TI__Intellectual 1670 points

Hi Gilberto,

The recommended pull up resistor would be 100kΩ. But what is your turn on voltage ?

0 Gilberto Ermacovitch 7 days ago in reply to Tony Koulong

Prodigy 225 points

6.5V.

0 Gilberto Ermacovitch 7 days ago in reply to Gilberto Ermacovitch

Prodigy 225 points

 have attached a screenshot of my circuit.

0 Tony Koulong 7 days ago in reply to Gilberto Ermacovitch

TI__Intellectual 1670 points

Isn't your pull-up resistor suppose to connect to VIN?

0 Gilberto Ermacovitch 7 days ago in reply to Tony Koulong

Prodigy 225 points

The enable pin is directly connected to VIN via the optocoupler.
My question is regarding the need for a resistor to protect the enable pin. The manual states that it can be connected directly
 to VIN:
"EN 3 A Enable input to regulator. High = ON, low = OFF. Can be connected directly to VIN. Do not float."

0 Tony Koulong 7 days ago in reply to Gilberto Ermacovitch

TI__Intellectual 1670 points

Yes, you can pull the EN pin directly to VIN without using a pull-up resistor.

You can also, used a resistor divider (Which will cause some current leakage)

Or a pull up resistor (100k - 115k) and a transistor to pull down enable.

Also, check the EVM www.ti.com/.../snvu848.pdf

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LMR38025-Q1: Enable input leakage current