LMZM23601: Power Rail for PGOOD Pull-up Resistor

DO-Pro

Part Number: LMZM23601
Other Parts Discussed in Thread: PSPICE-FOR-TI

Hi,

I'm designing a step-down converter using LMZM23601 part. The anticipated input voltage applied to VIN pin is +5V and the output voltage of the converter is +3.3V. A 10K Ohm pull-up resistor on PGOOD pin will be connected to the separate independent +12V dc power rail. Although this value seems to be within Absolute Maximum limits for PGOOD pin that allows +16V max, I still have a concern regarding this voltage being higher than VIN input power.

Q1: Is it OK to use PGOOD pull-up voltage rail higher than VIN?

Q2: I tried to simulate this situation using PSpice-for-TI software and noticed that PGOOD never raises above VIN. Does it mean that there is a clamping diode between PGOOD and VIN pins or some other voltage-limiting circuit that limits the PGOOD voltage?

Please clarify this situation for me.

Regards,
Michael

over 4 years ago

0 Frank De Stasi over 4 years ago

TI__Guru 73015 points

Hello

I will contact the application engineer for this device and try to get back to you as soon as possible.

Thanks

0 Frank De Stasi over 4 years ago in reply to Frank De Stasi

TI__Guru 73015 points

Hello

Based on what the responsible engineer has told me, it seems that it is OK to apply 12V through the

pull-up resistor to PGOOD with 5V on the input to the converter.

I am not sure that the SPICE model will show the true behavior under these conditions.

The best way to be sure is to use a TI EVM and test under you particular conditions.

Thanks

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LMZM23601: Power Rail for PGOOD Pull-up Resistor