ISM330DLC Low Power Mode

[NSmit.9]

Trying to get the lowest power out of this device, but it seems to draw at least 900uA of current when even the accel and gyro are disabled. Any suggestions on how to get the current draw of this device lower? Here's my setup:

1. Custom PCB
   1. normal current draw without IMU 0.1mA
   2. normal current draw with IMU and below settings: 1mA
2. Connections
   1. 4-wire SPI bus w/ CS (shared with other IC with separate CS)
   2. pins 2, 3, 6, 7 GND
   3. pins 5, 8 to 3.3V
   4. all others NC
3. Firmware
   1. IMU gets turned on with ODR 12.5 for accelerometer and gyro
   2. I2C gets disabled for SPI only
   3. Accel and Gyro power mode set to 1 (HP off)
   4. a few samples are read
   5. IMU ODR set to 0 for accel and gyro
   6. read accel and gyro values once
   7. Go to sleep (1mA current draw)

I can confirm that by removing the IMU the current drops to the expected 0.1mA. Any ideas as to why it's consuming so much current, relatively speaking?

[Federica Bossi]

Hi @NSmit.9 ,

Can you connect also SDA, SDO and SCL? And then measure the consumption in power down?

Thanks

[NSmit.9]

Federica,

We currently have the following connected:

• SDA (pin 14) connected to SPI MOSI on the STM32, no pull resistors
• SDO (pin 1) connected to SPI MISO on the STM32, no pull resistors
• SCL (pin 13) connected to SPI SCLK on the STM32, no pull resistors
• CS (pin 12) connected to SPI CS on the STM32, no pull resistors

Was that what you were referring to? Also, a few other questions on signal connections:

1. is it better/more efficient to connect the unused signals (SDx, SCx, SDO_Aux) to VDDIO or GND when unused?
2. Should INT1 and INT2 be floating or tied to a rail if unused? They are currently floating.

Saving a couple of microamps here would be much appreciated.

 

[Federica Bossi]

Hi @NSmit.9 ,

You can refer to table 1 in datasheet:

It's ok to leave INT1 and INT2 floating if they are used as output, otherwise you should polarize them through a pull up.