I am using an LTC6811-2 battery monitoring IC for monitoring a battery pack. I am also using an AD8205 to sense the current between battery and load. To control both ICs, I am using an STM32F401 microcontroller. I am using a 36V nominal 2500 mAh battery pack. Its maximum voltage is 42V.

Microcontroller power consumption:

  • supply voltage : 3.3v
  • input current : 160 mA max

AD805 (current sense amplifier ) power consumption :

  • supply voltage : 5v
  • input current : 20 mA

Since my microcontroller input supply voltage is 3.3V, I have used a buck converter to buck the voltage from 42V to 3.3V to give as an input voltage to my microcontroller.

The problem is the current sense amplifier supply voltage is 5V. I cannot use one more buck converter to get 5V again it will end up in more components and power loss.

Can I use the regulated output of my battery monitoring IC to power my current sense amplifier. In the datasheet of my IC is given like.

enter image description here

It is given like Vreg pin is used to power the internal SPI and ADC converters, but in my design I am giving the power of SPI through 3.3 v of microntroller. This is also mentioned in the datasheet.

Since I am not using Vreg output pin of my battery monitoring IC to power my SPI. Can I use it to power my current sense amplifier so that I can reduce the component count and reduce the extra power consumption. Like this:

enter image description here

Is it possible or should I go with the current sensing amplifier with 3.3 v as input voltage?

Please find the attached data sheet of battery monitoring IC : enter link description here

Current sensing amplifier datasheet:enter link description here


1 Answer 1


You can use Vreg to power up AD805. This device uses only 2 mA current (max). Linear (now Analog Devices) use Vreg to power EEPROM in demoboard for LTC6811 which has also only mA current consumption.

PS. But your schematic is wrong. You must use NPN transistor to Vreg as shown in datasheet.

  • \$\begingroup\$ Thank you so much . \$\endgroup\$
    – Muthu
    Apr 14, 2020 at 17:38

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