TPS543620: Only switching a 2MHz

Walter Britton

Part Number: TPS543620

Hello,

We have a well regulated supply. Nevertheless we are not able to change the switching frequency. It was designed for 1MHz (11.8Kohm resistor to ground on pin 1) but it always goes to 2MHz. We tried changing it to 26KOhms to try and select 500KHz with no luck. This is happening on different supplies on the same PCB and different PCBs. -- I would suspect a design error but we reviewed the schematic and PCB and have not found anything that could cause this.

I can send the schematic circuit if desired.

Thanks for the help.

BR.

over 2 years ago

0 Tahar Allag over 2 years ago

TI__Mastermind 30570 points

Walter Britton

Hello Walter,

The recommended resistor for 500KHz is 24.3Kohms for E96 and 27Khms for E12. 26K will not do it for both.

Can you please send me the schematic and test conditions (VIN, VOUT, IOUT...etc)? Also, it is good to know that the layout recommendation for that pin is followed

Thanks!

Tahar

+1 Yitzhak Bolurian over 2 years ago

TI__Mastermind 18370 points

Hi Walter,

Please measure the actual resistance on the pin.

There seems to be a short (low resistance) to ground that prevents you from choosing the right frequency and forces 2.2 MHz of operation.

Regards,

Yitzhak Bolurian

0 Walter Britton over 2 years ago in reply to Yitzhak Bolurian

Prodigy 30 points

Thanks. There was an IC that should have been open circuit driving the signal low.

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TPS543620: Only switching a 2MHz