Power Consumpion on i2c on esp32 on arduino framework

Question

I am relatively inexperienced with electronics so be gentle please.

I am trying to interface a VEML7700 photodiode sensor with a Firebeetle ESP32 using platform.io and arduino framework.

The connection and library usage was very straightforward so I got it up and running almost immediately.

The schematic is in the image

The problem is when I tried to measure the power consumption. According to the datasheet, the VEML7700 should consume around 40-60 µA. When I measure the power consumption with it connected on the esp32 I get 540 µA. If I disable the sensor I get a 480 µA consumption, which means that it turns off, and there is a 480 µA draw somewhere.

The strangest thing happens when you disconnect the Vcc. The sensor still works and outputs data.

If I do the same thing with another sensor (BME280 barometric sensor) connected on its own, I get an equivalent consumption (around 500 µA)

If I connect both of them in series, I get double the power consumption (around 1 mA).

The same consumption happens even if I dont initialize the i2c bus. Or even if I have the SDA & SDL completely disconnected.

If you connect the sensors to a power supply directly with 3.3V and Vin, you get the consumption that they say on the datasheet (around 50 µA each), so I am off by an order of magnitude, even if I have the sensors disabled on the code.

I tried the same thing on an arduino NANO with a single sensor and I get 80 µA with the sensor enabled and 20 µA with the sensor disabled, so this appears to be working correctly.

Does anyone have any idea what the reason may be?

Thank you.

Edit: the same thing happens with the esp32 dev kit 4 which is the official dev kit

Answer 1

The extra current draw is likely due to the VEML7700 eval board having four 10k pull ups total on the SDA and SCL lines

These will draw power as long as the VEML7700 or the ESP connected to it are talking over I2C and there is power on the resistors from Vin and the VEML7700's internal 3.3v. If you want to increase these resistor values this will decrease the current draw of the system, but may also affect communication speed.

I recommend not using internal pull ups on the esp32 without some kind of protection like a clamp or voltage divider, as these pull ups will pull the I2C lines up to 5v and the VEML7700 does not appear to have internal over-voltage protection over 3.6v.