LM2623: Suitable Device for Boost from 1V to 12V, I=200mA

Matthias Schumacher

Part Number: LM2623
Other Parts Discussed in Thread: LM2621, TPS61022, TPS61089, LM2662

I want to boost from Vin=approx.1V to Vout=12V. Iout should be 200mA.

The input voltage should be as low as possible because the source will be a 2.5V supercap. So at the beginning Vin will be 2.5V and decreasing constantly. However the boost circuity should switch off at a very low Vin in order to get the maximum out of supercapacitor's charge.

Will a LM2621 or LM2623 be suitable, or which other step-up converter do you suggest?

Thank you.

over 5 years ago

0 Zack Liu over 5 years ago

TI__Mastermind 34201 points

Hi Matthias,

LM2623 could not work at Vin=1V, Vout=12V condition because it will triggers the maximum duty cycle limit. LM2621 minimum input voltage is 1.2V and it will also triggers its the duty cycle limit.
TPS61022+ two stage charge pump circuits is one choice. TPS61022 has a 1.8V minimum input voltage for startup and valley current limit is 8A, which is big enough for this application.

0 Matthias Schumacher over 5 years ago in reply to Zack Liu

Prodigy 70 points

Dear Zack Liu,

Thank you for your input. Which charge pump do you suggest to get the 12V then (assuming that I use the TPS61022 to go from 1V to 5.5V)? No need to stick to LM2621 or LM2623!

Secondly: In theory I could also modify my power consumption, and I go with lower Vout. 10V will be however the absolute minimum. So if we choose Vin=1V, Vout=10V, I=160mA. I assume that you would also suggest not to use one single charge pump, correct?

Thank you

Matthias

0 Zack Liu over 5 years ago in reply to Matthias Schumacher

TI__Mastermind 34201 points

Hi Matthias,

TPS61022 maximum output voltage is 5.5V. If Vout is 10V, Iout=160mA, TPS61022+one single charge pump would work.
Do you have any external 3.3V or 5V voltage rail on board? If there is, use one single TPS61089 and supply the device Vin pin with 3.3V or 5V.

0 Matthias Schumacher over 5 years ago in reply to Zack Liu

Prodigy 70 points

Dear Zack Liu,

Thank you, but I don't have any external 3.3V or 5V, so I need to go with TPS61022 and charge pump.

Would it work like that (Vin=1V to 2.5V):

- TPS61022 (L=0.8µH (Fastron 1616FPS-R82N-0), Cin=10µF (ceramic); Cout=2x22uF (ceramic)) in PWM Mode to get 5.5V and then

- LM2662 in voltage doubler mode (C1=C2=10uF (ceramic) + FC-Pin directly connected to V+Pin) to get 11V with Iout=approx. 200mA

Do I need to increase capacitors or change the inductivity? As overall pcb size matters (mainly thickness), I want to use ceramic capacitors, whenever possible.

Regards,

Matthias