LMR62421: LMR62421 3V/5V input with 5V/1A output

Zhou JianQiang

Part Number: LMR62421
Other Parts Discussed in Thread: TPS61023

Hi :

I want to drive a 2*2W DAC by single cell Li-on Battery.

In my design, I will turn off battery when voltage less than 3V, meanwhile with USB plug in, I want to use 5V instead of battery.

I think 5V/1A is enough for this DAC and LMR62421 is Ok for my design, am I right?

But I don't find efficiency in datasheet, WEBENCH® POWER DESIGNER also don't support this case.

Can anyone tell me how to choose the INDUCTOR and the diode?

0 Zack Liu over 4 years ago

Hi Jianqiang,

You can take a look at using boost converter TPS61023. This device is a integrated boost converter and has higher efficiency.

0 Zhou JianQiang over 4 years ago in reply to Zack Liu

But TPS61023 is hard to solder, and lmr62142 with SOT23 is easy to solder, that why I choose this one.

0 Zack Liu over 4 years ago in reply to Zhou JianQiang

Hi Jianqiang,

It's quite marginal to let LMR62421 work at 3V Vin, 5V 1A output condition.

TPS61023 is more recommended.

0 Zhou JianQiang over 4 years ago in reply to Zack Liu

Do you mean in 3V Vin 5V/1A output condition, the input current will reach 5V*1A/0.8/3=2.083A which is close to 2.1A?

If so, 3.3V input should be OK?

0 Zack Liu over 4 years ago in reply to Zhou JianQiang

Hi Jianqiang,

3.3V input should be OK for LMR62421.

0 Zhou JianQiang over 4 years ago in reply to Zack Liu

Can you give me some advice about INDUCTOR selection?

which model number should I use?

0 Zack Liu over 4 years ago in reply to Zhou JianQiang

Hi Jianqiang,

You can select a 10uH inductance with Isat>2.5A.

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