LM5165-Q1: Output voltage won't change and Can't get the desired voltage output

user5791980

Part Number: LM5165-Q1
Other Parts Discussed in Thread: LM5165

Hi,

We are using LM5165-Q1 (SSOP) for a 5V design. However, we got 7.8V output regardless how the FB resistors changed.The schematic is based on Webench design. Currently, we have RT and ILM shorted to ground. HYS pin is floating and SS connected to a 0.056uF to grpund. Th einductor is 150 uH. as mentioned earlier, the output stay the same (around 7.8V) no matter how the feedback resistors changed. Thank you.

Best Regards,

Chun-Te Li

over 4 years ago

0 Timothy Hegarty over 4 years ago

TI__Mastermind 49647 points

Hi Chun-Te,

The LM5165-Q1 in VSSOP-10 package is only available in fixed 3.3V version (P/N LM5165YQDGSRQ1). Connect the output directly to the VOUT/FB pin of the LM5165 (no feedback resistors required).

Note that you can use the LM5165 quickstart calculator http://www.ti.com/tool/LM5165DESIGN-CALC to assist with component selection. When operating in PFM mode (RT tied to GND) and ILIM at max setting, 150uH establishes a very low switching frequency. I recommend reducing the inductor to ~47uH.

Regards,

Tim

0 user5791980 over 4 years ago in reply to Timothy Hegarty

Prodigy 140 points

Hi Tim,

Thanks for the response. For the low power mode, which one would be better, PFM or COT? The system should run under 10mA for 99% of the time and 80mA or more for the 1% of the time.Thank you.

Best Regards,

Chun-Te Li

0 Timothy Hegarty over 4 years ago in reply to user5791980

TI__Mastermind 49647 points

Chun-Te,

PFM is slightly better in terms of efficiency at light load (below 10mA). Take a look at the LM5165 COT and PFM EVM user's guides for more detail.

Regards,

Tim

Power management

Power management forum

LM5165-Q1: Output voltage won't change and Can't get the desired voltage output