LP3856: /SD functionality

Gregory Duperon

Expert 6750 points

Part Number: LP3856

I'm trying to better understand the description here.

Is it safe to directly tie the /SD pin to VIN if shutdown functionality is unused?

Or do I still need to pull up through a 10kOhm resistor?

over 4 years ago

0 Kyle Van Renterghem over 4 years ago

TI__Genius 14245 points

Hi Gregory,

Yeah the wording in this old datasheet isn't the most clear but the 10k resistor should be used even when tying SD to Vin.

0 Gregory Duperon over 4 years ago in reply to Kyle Van Renterghem

TI__Expert 6750 points

Hi Kyle,

Can you explain why the 10kOhm pull-up is needed? Would /SD pin be damaged if tied directly to VIN?

Thanks.

0 Kyle Van Renterghem over 4 years ago in reply to Gregory Duperon

TI__Genius 14245 points

Hi Gregory,

Unfortunately the information that we have for these old designs is limited so I don't know the exact reason for this 10K requirement on the SD pin. However if I were to hypothesize, I suspect that it is there to protect the device by limiting the amount of current and/or the dV/dt of the signal which the SD circuitry is exposed to.

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LP3856: /SD functionality