VL53L8CX Power consumption is too high

[simonbelanger]

Hello,

in the datasheet for the L8, the power consumption for a low power mode such as autonomous 4x4, 1Hz frequency and 5 ms integration time is given to be 1.6 mW . 

I tried measuring the power consumption for a similar mode which is autonomous 4x4 @ 1Hz and 2 ms integration time, which should be the mode with the absolute minimal power consumption. 

However, I measure important currents on both CORE_1V8 and AVDD pins of the chip. For CORE_1V8, the average current is 16.87 mA and for AVDD I get 7.08 mA average. These currents lead to a power consumption of around 68 mW which is far from the datasheet and I was wondering if I was doing something wrong. Here are the measurements for the currents 

As you can see, the period between pulses is 1000 ms which validates that ranging frequency was set to 1 Hz. Also, there is only one laser pulse with a period (integration time) of 2ms, which validates that we are indeed in 4x4 (else we would have 4 pulses) and that we are not in continuous mode. 

The current levels when a ranging is performed does not bother me. However, what bothers me is the current drainage between rangings that is totaling 23 mA. It should not be that high. Those current levels are the same when I stop ranging and the device is in HP idle. This issue looks a lot like Solved: VL53L5CX Power Consumption - STMicroelectronics Community but for VL53L8CX instead of VL53L5CX. However, the resolution given in the post to read the data another time by calling vl53l5cx_get_ranging_data() to clear an interrupt does not fix the issue in my case. Also, I don't believe interrupt have to be cleared manually, they are cleared automatically after 100 us which is what I am getting.

My config looks like this : I boot the sensor, then init and then i set the mode, resolution, integration time and frequency. Then I start_ranging() and after I poll the data by checking if it is ready *_is_data_ready() and getting the data while it is 

*_get_data.

 

So my questions are:

- Is there something I am doing wrong in the setup + operation of the sensor?

- What would be the typical current inbetween rangings for AVDD and CORE_1V8?

 

Thanks in advance

 

 

[John E KVAM]

Translated from my French expert:

"Normally the switch is automatically cleared after 100μs, and the sensor automatically goes into low power mode. It seems that the customer can see this kind of thing (even if the power is higher than expected). It's rather positive, it shows that it's not a SW or FW problem.

We are left with the HW. Can you confirm that all the pins are well connected as advised in the DS? No floating pins or any particular setup?"

I agree there isn't much one can do wrong in the SW. So, let's start by double checking the HW. 

- john

[John E KVAM]

I had someone I trust recheck it. 

And he gets a plot more in line with our datasheet:

I'm not sure you can read that but it's a plot of AVDD and 1.8 in mA. And it goes from a high of almost 60 and down to very near zero. 

He also commented:

"However their core_1V8 is a bit higher (still in spec).

"AVDD is much lower and a little concerning. Too low and we will not fire the laser.

"It’s almost as if it is collapsing. Which can happen if there is too much signal such as a very close bright target (e.g. halogen lamp).

"I get approx.1.9mW on 4x4 at 1Hz (2ms int)

"Important to make the measurement with only the L8 on the supply not other devices powered at the same time."

I'm a software guy trying to interpret this, but I'm hoping this helps.

- john