LMQ62440-Q1: Debugging, Off behaviour not as expected

Teva Zanker

Part Number: LMQ62440-Q1

Tool/software:

Hi,

I'm trying to debug the fixed output 3.3V LMQ62440BPPQRJRRQ1.

It appears so far to operate appropriately when the enable output is on however there are a few issues with the off behaviour.

1. When the device is first powered on the ouput sits at 0.4V, not zero or high impedance

2. When the enable pin is activated and de-activated, the power output goes from 0.4V (initial off) to 3.3V (on) to 3.1V (apparently off).

It appears as though the off state voltage is a DC output from the regulator as there does not appear to be any switching going on during the off state, just a DC 3.1 or 0.4 V

The following are my schematic

and layout

Any help would be greatly appreciated!

7 months ago

0 Joshua Austria 7 months ago

TI__Mastermind 24115 points

Hello,

Thank you for detailing your problem, schematic, and layout.

Our first recommendation in debugging this issue is to conduct an ABA swap with this IC, so we can understand if your issue is IC or system based. Can you please utilize this EVM, and swap the IC from your system onto that EVM? Then conduct the same tests that you did with your system on the EVM and see if the issue(s) persist.

Thank you,

Joshua Austria

0 Teva Zanker 7 months ago

Prodigy 10 points

I found the cause, it was another part of the design that was interfering with the 3.3V lines. The regulator design above works well now!

Thanks!

0 Joshua Austria 7 months ago in reply to Teva Zanker

TI__Mastermind 24115 points

Hi Teva,

Sounds good! I will close this thread for now. Please confirm your resolution by clicking the TI Thinks Resolved button.

Thank you,

Joshua Austria

Power management

Power management forum

LMQ62440-Q1: Debugging, Off behaviour not as expected