ADXL345 power consumption

Q 

We use a ADXL345 in a product were we used to have a power consumption around
42µA. In the latest shipment of this product we use the same components and
firmware but the power consumption is around 49µA. We have investigated the
matter and found that the ADXL345 is the cause of the higher power use. I have
switched components with devices from previous batches, so two new and two
older devices. And found out that they consume different amount of power with
the same settings. The writing on the components is presented below.

We use Low power mode and a output rate of 25Hz on all devices.

40µA                   |                           47µA

345B                   |                           354B

#042                   |                           #223

6712                   |                           8306

PHIL                   |                           PHIL

                       |

345B                   |                           354B

#141                   |                           #223

7142                   |                           8306

PHIL                   |                           PHIL

 
Do you have an idea why we get this increase in power consumption? How much
deviation from 40µA is tolerated in this component. Is there any record of bad
batches. Can our producer have handled the component badly and then caused this
in some way? Is there something in particular that they have to consider when
working with this component?

 

A 

Higher supply voltage can result higher current consumption : see Figure 33 in
the datasheet. As you know, 40uA @25Hz ODR, LPM, this is got @2.5V supply and
it is a typical spec but not guaranteed.

You can check the histogram of current consumption @100Hz ODR, 140uA is the
typical value, some parts can reach 115uA or 185uA (Figure 31 in datasheet).
The tolerance is around 32%, but again, this is the typical spec on datasheet
which means not guaranteed.
So, I do not think there is something wrong with ADXL345 if its current
consumption vary a little. 42uA->49uA, 17%.

If power consumption is critical to your application, I would suggest to use
ADXL362.