Using an LIS3DH at LiPo Voltages

Question

The LIS3DH 3-axis accelerometer specifies that it's supply voltage should be between 1.71 V and 3.6 V. For most applications, this just means you are using either 1.8 V or 3.3 V as your main rail. However, page 12 of the datasheet also mentions that the absolute maximum for the supply voltage is -0.3 V to 4.8 V. Given that it includes a negative voltage, I'm going to assume that this rating is the safe voltage range that can be applied to the VDD pins.

It does specifically mention that "functional operation of the device under these conditions is not implied", but could I safely operate this device directly and exclusively from a LiPo battery? 2.7 V to 4.2 V is well within the absolute ratings, but what exactly am I risking at this point? I'm also not the first one to be using these kinds of voltages (ST Forums Thread).

Before you ask, using an LDO doesn't make a lot of sense for my application due to the extra circuitry to facilitate a multi-voltage I2C bus and limited PCB real-estate. I didn't feel like it was strictly necessary to include detailed info about my application for my specific questions, but I'd be happy to provide it if needed.

LIS3DH Datasheet

Answer 1

The absolute maximum ratings are the limits at which the device may be damaged. The manufacturer makes no claim about the device operating correctly between the max rated supply and the absolute max supply. You won’t damage the device permanently but it may not give accurate readings.

You can probably drop the voltage into a good range by putting a diode in the supply path.

Answer 2

Li-Po voltages will not hurt the accelerometer with a supply of 1.71V - 3.6V.
The Li-Po's fresh charge will usually go as high as 4.2V.
4.2V will not damage the accelerometer but likely will not work well.

The problem is that at a light load a Li-Po may not get to 3.6V until well past a 90% discharge. This is the discharge curve for a 2800 mAh battery. So 0.2C = 0.2 x 2800 mAh = 560 mA discharge rate.

source EEMB LIR18650 datasheet

---

This accelerometer only draws 2 µA so it's not enough current to use a switcher.

You cannot use the Li-Po directly. You could use a button cell.

I assume you have another device to work with this accelerometer.
You just need a voltage between 1.71V and 3.6V.
Why is that a problem?

---