LMZ23605: Enable pin impedance

Thanks Andrew, we are actually seeing 6.5V. There is concern since this is above the ABS max rating (5.5V) for the part. Since the EN is disconnected on the PCB, the pull up is coming from inside the part. Is this a reliability concern?

As I look at the block diagram, there is a 2Megohm resistor shown pulling the EN pin to Vin. There is also mention of a 21uA current source that kicks in after the device is enabled.

Andrew,

Paragraph 8.2.2.2 of the datasheet states   “the Enable input may be left open circuit and the internal resistor will always enable the module”

So if this is true, how do we explain the ABS max violation (5.5V max but we measure 6.5V)?

Thanks,

Steve

Andrew, 

We state at the start of 8.2.2.2 that the pin may be left open if EN is not needed without any limitation on the input voltage, does this only apply for Vin < 5.5V since there is a pull-up (2MegOhm) to Vin?

Is there some Vin voltage limit where the EN pin can be left open?

Hi Steve,

For your application it sounds better if if there was a resistor divider rather than letting the 2 MOhm pull-up do the work.

Thanks,
Andrew

Thanks Andrew but this "open EN pin" design has already been shipped in multiple products and is in the field. We need an assessment of the reliability of this configuration.

Hi Steve,

I will check with the designer if it's ok.

Thanks,
Andrew