0
\$\begingroup\$

I am trying to build a circuit containing the LSM6DS3 IMU (Datasheet) to be powered by the Sparkfun 110mAh Lithium battery PRT-13853 (Datasheet).

According to the datasheet of the IMU, it is able to operate in a voltage range from 1.71 to 3.6V (page 23):

imu datasheet electrical characteristics

The battery provides a voltage between 4.2 and 2.8V (page 4):

battery datasheet electrical characteristics

Edit: according to another question, LiPo batteries should not really be discharged below 3.7V. That should not change anything for my question though.

This means the batteries voltage stays high enough IMU during the entire discharge cycle, but must be regulated down.

Given the low current consumption of the IMU, I thought about using an LDO linear regulator. Would the TLV755P be a suitable regulator? If not, what alternatives would be better and why?

\$\endgroup\$
5
  • \$\begingroup\$ Lithium batteries have nominal voltage of 3.7V, it would not have nominal voltage of 3.7V if 3.7V would be the cut-off voltage. The cut-off voltage is near 2.8-3.0V, but not 3.7. You could regulate the battery voltage down to 1.8V, but then the IO voltage on the MCU should be 1.8V too, or implement some kind of level conversion if you have 3.3V MCU. The regulator should be fine. \$\endgroup\$
    – Justme
    Commented Jan 12, 2021 at 17:20
  • \$\begingroup\$ LiPo batteries should not really be discharged below 3.7V - you have that wrong so, where in that link did you read that? \$\endgroup\$
    – Andy aka
    Commented Jan 12, 2021 at 17:38
  • \$\begingroup\$ @Andyaka in the comments of the question \$\endgroup\$
    – Lukas_Skywalker
    Commented Jan 12, 2021 at 17:44
  • \$\begingroup\$ It was back in 2012 so maybe not true any more or, maybe it's a recommendation that can give you longer life. Not an expert but running down to 3 volts or a tad below has never produced red flags in other documents. \$\endgroup\$
    – Andy aka
    Commented Jan 12, 2021 at 17:47
  • \$\begingroup\$ Similar question: Low power ESP8266 LDO or switching regulator \$\endgroup\$
    – maxschlepzig
    Commented Mar 13, 2022 at 17:12

1 Answer 1

Reset to default
1
\$\begingroup\$

LDO's are suitable for the use of batteries, but you are correct that the battery needs to be protected from overdrawing the voltage (low voltage condition).

The TLV755P has an enable pin that can be used to shut down the LDO at 1.28V (falling voltage).

schematic

simulate this circuit – Schematic created using CircuitLab

So if you do use an LDO make sure that it has an enable

Also, make sure you calculate the power dissipated

Power = Voltage drop x current through LDO

(The voltage drop is the battery voltage - LDO output voltage)

If its more than ~250mW then it would be a good idea to look into how hot the part will get.

\$\endgroup\$
1
  • \$\begingroup\$ If you want to protect your battery, isn't it safer to connect a voltage detector IC (such as the MCP112/TC54) that implements hysteresis to the enable pin - instead of using a voltage divider? I mean without the hysteresis you might get weird on/off oscillation when the battery voltage reaches the threshold ... \$\endgroup\$
    – maxschlepzig
    Commented Mar 13, 2022 at 17:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.