LM43601: Webench design not working as expected sometimes.

Hector Martinez

Prodigy 20 points

Part Number: LM43601

Hello TI,

I've been working with a negative DC-DC Synchronous Step-Down Voltage Converter with the LM43601:

Layout design followed from recommendation:

3D view.

I'm using AC/DC power supply of 15V from "IRM-30-15" from Meanwell:

The setup rise time is the following:

At full load: 1500ms.

Is there a problem in the setup configuration of the schematic causing sometimes the voltage stays in +1V output instead of -15V?

I'm guessing the soft-start time can be modified so it can start after the 1.5secs but I'm not sure about it.

Also if I make a short between output and GND in a matter of ms (with a tweezers), it reconfigures the output to -15v working well.

Let me know what can we achieve to always make a reliable output of -15V, it's for an audio application for Opamps.

Best regards,

Héctor.

over 4 years ago

0 Andy Chen over 4 years ago

TI__Mastermind 34875 points

Hi Hector,

Can you upload the actual application circuit in higher resolution?

B R

Andy

0 Hector Martinez over 4 years ago in reply to Andy Chen

Prodigy 20 points

The next PDF shows detailed information about the circuit.

MinimixerNegativePWRSPPLY.pdf

Best regards,

Héctor.

0 Andy Chen over 4 years ago in reply to Hector Martinez

TI__Mastermind 34875 points

Hi Hector,

check the circuit design:

1. SYNC pin must be connected to LM43601 GND pin, NOT the circuit ground.

2. VCC cap must be ceramic cap 1uF 16V, now the E-cap C12 should be rotated 180C for correct connection

3. Remove Cff1 120pF

4. Cout1/2/3 should be 35V or 50V rating.

Pls try if above improve the problems.

B R
Andy

0 Hector Martinez over 4 years ago in reply to Andy Chen

Prodigy 20 points

Hello Andy,

Thanks for the recommendations, so far it has worked really well, I will still be testing several days to check that always keeps in -15v.

Aproximate 250ms for the start (yellow line) to get into -15v.

Also due to difficult manipulation of the IC to change SYNC pin to GND pin (Vout of -15v) I cut PCB layout traces that connect SYNC and BIAS pins that were together and solder them with a cable to GND PIN (VOUT of -15V).

The idea is that this is clean, so I will correct it from schematics and layout design so it could perform better.

Thanks again for the recommendations,

Best regards,

Héctor.

Power management

Power management forum

LM43601: Webench design not working as expected sometimes.