LM2936: about SD pin internal resistor

Tsukui Yusuke

Guru 21930 points

Part Number: LM2936

Hi,

Could you tell me about LM2936 SD pin?
Customer wants to know the resistor value installed inside the SD pin.

Since this IC operates when this pin is set to OPEN,
I think that a pull-down or pull-up resistor is installed.

Best Regards,
Yusuke / Japan Disty

over 6 years ago

0 Jason Song over 6 years ago

TI__Mastermind 23361 points

Hi Yusuke-san,

I checked the test available for this device, I could not find this information either. Please allow a few more days for me to investigate this.

Regards,
Jason Song

0 Tsukui Yusuke over 6 years ago in reply to Jason Song

Guru 21930 points

Jason-san,

Thank you for your response.
I'll be waiting for your reply.

Best Regards,
Yusuke / Japan Disty

0 Daddio over 6 years ago

Intellectual 515 points

Hello Yusuke-san,

There is no 'pull-up' or 'pull-down' resistor on the SD pin of the LM2936BM version.

The OFF function is accomplished turning on an NPN transistor with the base current coming from the SD pin through and effective ~ 450 k ohm series resistance. The purpose of the resistance is to limit the base current when the SD pin voltage is above the Vbe of the NPN transistor. This is not a true 'resistor' , rather leakage through a pseudo-FET (i.e. EPI-FET) structure.

Note that every LM2936 version has the SD structure on the die. The LM2936BM is the only version that wires the SD pad out to a pin, all other versions leave this pad un-wired (i.e. open).

0 Daddio over 6 years ago

Intellectual 515 points

Yusuke-san,

From the archives, in case this might help ...

LM2936B_Isd-vs-Vsd.pdf

0 Tsukui Yusuke over 6 years ago in reply to Daddio

Guru 21930 points

Daddio-san,

Thank you so much for your sincere correspondence to my requests.
I will report the customer the your response.

Best Regards,
Yusuke / Japan Disty

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LM2936: about SD pin internal resistor