LM2623: The design of 14V output system

Shaw Wong

Part Number: LM2623
Other Parts Discussed in Thread: TPS61085

Hi,

Our customer are evaluating LM2623 in their design, the input is super-capacitor and the voltage is 3V, the output voltage needed is 14V. In datasheet, the typical application is based on 5V output, and the BOOT, VDD and EN pin are connected to output directly. However, the maximum voltage of the three pin( BOOT, VDD, EN) is 10V, we can not connect these pin to output directly, so how should we design? Thanks!

over 7 years ago

0 Youhao Xi over 7 years ago

TI__Guru* 78060 points

Two options for your evaluatin: (1) tie these pins to VIN, (2) consider other TPS61xxx boost converters like TPS61085.

0 Shaw Wong over 7 years ago in reply to Youhao Xi

Intellectual 590 points

Hi Youhao,

Thanks for your reply. The minimum VIN voltage of TPS61085 is 2.3V, and it can not meet the needs of minimum input voltage. The first option may be a method, and besides, can we divide output voltage to 5V by two resistors, and provide to BOOT, EN and VDD pins? Thanks!

0 Zack Liu over 7 years ago in reply to Shaw Wong

TI__Mastermind 34231 points

Hi Shaw,

What's the input voltage range? You can also use a resistor and zener diode to get 5V for BOOT, EN and VDD.

Regards,
Zack

0 Shaw Wong over 7 years ago in reply to Zack Liu

Intellectual 590 points

Hi Zack,

The input voltage range is 0.8V-3V by a super-capacitor.

0 Youhao Xi over 7 years ago in reply to Shaw Wong

TI__Guru* 78060 points

You cannot use a resistor divider to provide voltage to those three pins. They take current from the output and the resistor divider will not allow that current. Also, Startup can be an issue when it is 0.8V. So, please consider the other option as we recommended a few days ago.

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LM2623: The design of 14V output system