LM2623: LM2623 boost from 1.2V to get 12V output

Steven Liu1

Part Number: LM2623

Hi Team,

My customer want to use the LM2623 for the boost from a super cap to 12V output.

As showed in the LM2623 datasheet, BOOT, VDD, EN and FB pins are not allowed to attached to the 12V, as the voltage of those pins must be below 10V.

I check the link which tell a reference design, which is suggested that the BOOT, VDD, EN and FB pins are connected to the input.

But my main concern comes from the super cap voltage, if it drops to 1V~1.2V, Can it still support the 12V output?

If considering the input of the voltage is 1.2V, how can we get the 12V output?

Expecting your response! Thanks!

https://e2e.ti.com/support/power-management/f/196/t/666808?tisearch=e2e-sitesearch&keymatch=LM2623

over 5 years ago

0 Zack Liu over 5 years ago

TI__Mastermind 34201 points

Hi Steven,

1. LM2623 operating range is 0.8V to 14V. But it needs a 1.1V startup voltage. It means if super cap is charged higher than 1.1V, the device could work until the vin drops below 0.8V. However, if super cap is already discharged below 1.1V, the circuit will never be activated.

2. A 5.1V voltage could be generated with a zener diode from 12V output voltage.

3. What's the load current? LM2623 current limit is not fixed.

0 Steven Liu1 over 5 years ago in reply to Zack Liu

TI__Expert 4380 points

Thanks for Zack's quick response!
The load current is 1A ~1.5A.
I think this might be a problem when input voltage is 1V~1.2V. May I know the minimum voltage that can support the LM2623 output @12V, 1A?

0 Zack Liu over 5 years ago in reply to Steven Liu1

TI__Mastermind 34201 points

Hi Steven,

Like I said in the email, the minimum vin should be higher than 6~7V. I think that's too high for the requirement.

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LM2623: LM2623 boost from 1.2V to get 12V output