LMZ12003: LMZ1200x enable pin internal pull-up value

Hi ,

Our expert will check this soon.

BRs,

Young

Hi Marina,

 Could you tell me why you need this internal resistance value? Usually we will not disclose the internal information to customer.

Thanks,

Nancy

We need it because in one of our designs we connect the EN pin of LMZ  to a +5V signal (with an external pull-down of 10K). We supply the LMZ with 12V.

If the +5V signal is in high impedance, which would be the expected value in EN pin? I guess that current would fllow through internal pull-up from 12V to EN, and maybe we would see voltage on EN pin (which is connected to +5V in our design). That could be a problem for us. 

Hi Marina,

The internal resistor from Vin to EN should be pretty high from datasheet 8.2.2.1 section as below.

We could not find the exactly value since the previous engineer is not at TI. Actually you don't need to know that value.

When you add 5V external voltage to EN pin. The voltage on EN pin would be 5V. The current flow through the internal resistor from Vin to EN does not affect your application.

Hope this helps,

Thanks,

Nancy

Hello Nancy,

thanks for your answer but it didn't resolve my issue. We need to know the value because we are doing a failure analysis of our desing. To create the +5V we have a converter with external inductance. We need to analyze what happens when this inductor is in open-state.What voltage can we expect in +5V/EN? Our external pull-down resistor is 10K, maybe you don't know the exact value of the internal pull-up resistor, but would it be around 10K, 100K, 500K?

I add a diagram to clarify it.

OK! Thank you.

Only one question, if  'L' on scheme is in open state, the voltage on EN pin would be set by the resistive divider formed by Rpull-up internal (aroung 1Meg) and Rpull-down external (10K); so the EN pin voltage would be around 0V. Is is correct?