LMZ3150x Output Disabled by Default

Stephen Bennett

Other Parts Discussed in Thread: UCD90120A, LMZ31503

Hello,

The LMZ31503/6 simple switchers are enabled by default, but in our application they must have their outputs disabled by default. They will be sequenced by a UCD90120A power monitor, but there is a time when power is applied to the LMZ device but the sequencer does not yet have power and so cannot guarantee to have the LMZ inhibit pin pulled low.

Essentially what my question boils down to is if there is a suggested approach to making the inhibit pin act as an enable pin instead?
Or, how can I ensure that the output is disabled until explicitly commanded to be enabled by the sequencer, regardless of the power state of the sequencer?

Thanks,
Stephen Bennett

over 9 years ago

0 Stephen Bennett over 9 years ago

Prodigy 80 points

If my understanding of the how this pin is connected internally is correct, then I believe the following circuit should work for my needs of ensuring the LMZ is inhibited by default, regardless of the power state of the UCD controller.

0 J Arrigo over 9 years ago in reply to Stephen Bennett

TI__Mastermind 28020 points

Yes, by applying a pull-down on the INH pin, the device will remain disabled until the voltage on the UCD90120A goes high and the voltage on the INH/UVLO pin is above 1.3V.

Power management

Power management forum

LMZ3150x Output Disabled by Default