LMZM23601: LMZM23601inverting output -5V does not work

Miguel Ángel Corchero

Prodigy 20 points

Part Number: LMZM23601

Tool/software:

Hello,

I am using LMZM23601 in inverting buck-boost configuration:

Vin: 12V

Vout: -5V @ 0.5A.

I designed the circuit from Webench simulation, now I have the real design as prototype but the -5V output is not present and a 0.239V is measured instead. As the Webench schematics shows, the MODE/SYNC pin is left floating but the simulation runs well and get the -5V output. In the datasheet, it is mentioned that this pin should not be floating, then I tried to tie it to GND but the same output voltage 0.239V is measured. ¿Could the LMZM23601 be damaged due to left it open on first startup?

Regards,

Miguel.

4 days ago

0 Frank De Stasi 3 days ago

TI__Guru 73575 points

Hello

It is possible that the module has been damaged.

However, connect the MODE pin to the ground pin of the module, not the system ground and test.

Please send your schematic.

Thanks

0 Miguel Ángel Corchero 3 days ago

Prodigy 20 points

Hello,

Yo can see the schematic in the attached image. As I could see, several assembled boards have the same problem.

Thanks for your support.

0 Miguel Ángel Corchero 3 days ago in reply to Frank De Stasi

Prodigy 20 points

0 Frank De Stasi 2 days ago in reply to Miguel Ángel Corchero

TI__Guru 73575 points

Hello

Your schematic seems OK.

Try replacing the regulator and connecting MODE to the regulator ground.

What kind of load are you using ?

Thanks

0 Miguel Ángel Corchero 2 days ago in reply to Frank De Stasi

Prodigy 20 points

Hello,

I replaced the chip and connected MODE to ground already, but no changes has been detected. The load is a opamp, I guess the current consumption is very light, so I tried to disconnect the opamp and connected different resistive loads, such as 1K, 100 Ohm and 33 Ohm, then the output voltage never gets -5V but is even closer to 0V.

Best regards.

0 Frank De Stasi 1 day ago in reply to Miguel Ángel Corchero

TI__Guru 73575 points

Hello

Be sure that your diode is oriented correctly.

Can you send an image of your PCB layout.

Thanks

0 Miguel Ángel Corchero 1 day ago in reply to Frank De Stasi

Prodigy 20 points

Hello,

Yes, the diode is well oriented. Please, see the attached PCB screenshot.

0 Frank De Stasi 20 hours ago in reply to Miguel Ángel Corchero

TI__Guru 73575 points

Hello

What is your load ?

Can you test with no load.

Thanks

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LMZM23601: LMZM23601inverting output -5V does not work