WEBENCH® Tools/LM3478: LM3478 and the CSD16321Q5

Robert Butts

Part Number: LM3478
Other Parts Discussed in Thread: CSD16321Q5

Tool/software: WEBENCH® Design Tools

I used the Workbench designer to come up with a 3.7-4.2V to a 12V voltage converter. The design uses the LM3478 voltage regulator along with the CSD16321Q5 Mosfet.

I made a circuit board following the schematic. With the Mosfet in the circuit the input voltage is getting pulled down to 0.28 volts.

I'm not sure how to attach the schematic.

over 5 years ago

0 Garrett Roecker over 5 years ago

TI__Mastermind 21720 points

Hi Robert,

Thanks for using the LM3478.

Please post the schematic that you have created. Also please check and see if the COMP voltage is high (~2V) and if the duty cycle of the DR pin is 100%.

Thanks,

Garrett

0 Robert Butts over 5 years ago in reply to Garrett Roecker

Intellectual 260 points

Is there a way to attach a file? I"ll try inserting it but it doesn't look right. I'll have to get back to you regarding the voltage and duty cycle.

mkr-1-pg1.pdf

0 Garrett Roecker over 5 years ago in reply to Robert Butts

TI__Mastermind 21720 points

Hi Robert,

Looking at the schematic the MOSFET is connected incorrectly. The drain of the MOSFET should be connect between L1 and D1. The source should be connected to R6. With the way it is connected now the input voltage will be shorted through the body diode of the MOSFET.

Thanks,

Garrett

0 Robert Butts over 5 years ago in reply to Garrett Roecker

Intellectual 260 points

Thank you. I'm changing it now. I won't know if this resolves my issue until I get the new circuit board back so I'll check off that it resolved my issue. I'll repost if there is still a problem.

Power management

Power management forum

WEBENCH® Tools/LM3478: LM3478 and the CSD16321Q5