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With the MMA8452, it claims that it draws 44uA when ODR = 100Hz in Normal Mode.

However, I'm measuring 1.5mA when ODR = 100Hz. Does anyone know how this could be the case? In Low Power Mode, I'm getting almost identical values. I get even higher values in High Resolution mode.

I'm using a 100R shunt and I'm getting the same values with a scope and with a DMM. I'm using a GY-45, but the I2C pull-ups wouldn't draw that much more current - right?

Any help will be appreciated.

UPDATE 1:

Here's the circuit for GY-45

enter image description here

I'm tried powering it by using the VCC_IN power line with 3.3V and VCC_3.3V with 3.3V. Same measurements.

I did some more measurements. The Vds across the NFETs are around 0.12V. The voltage across the two left 4.7K are around 0.08V and the voltage across the two right 4.7K are around 0.02V. Do these figure help an explanation?

UPDATE 2:

I've desoldered the LDO and have supplied 3.3V and 5V to Vin, but same measurements.

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  • \$\begingroup\$ Circuit diagram? \$\endgroup\$
    – Andy aka
    Commented Sep 28, 2015 at 20:11
  • \$\begingroup\$ What's all the other stuff on that module? And without knowing how everything is connected it's hard to tell what might be wrong. \$\endgroup\$
    – Arsenal
    Commented Sep 28, 2015 at 20:13
  • \$\begingroup\$ Sure. I've updated my question with the circuit. \$\endgroup\$
    – John M.
    Commented Sep 28, 2015 at 20:17
  • \$\begingroup\$ Unfortunately it's on the module. I've tried powering it through VCC_IN and through VCC_3.3V - same measurements though. \$\endgroup\$
    – John M.
    Commented Sep 28, 2015 at 20:27
  • \$\begingroup\$ if SDA and/or SCL are held low for whatever reason that 2mA is reasonable. \$\endgroup\$
    – Vladimir Cravero
    Commented Sep 28, 2015 at 20:31

2 Answers 2

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Your "MMA8452" may be out of spec or faulty.

What to expect buying cheap electronic components from eBay

one thing I have found to be particularly diagnostic is how much current an IC draws... I have run into several cheap sensors that give decent readings, but never go into low current sleep modes.

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Current seems specced at Vdd=2.5 V. I suppose using 3.3V can increase your current draw, but I would hope not as much as you're seeing.

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  • \$\begingroup\$ I've tried Vdd=2.3V and Vdd=2.5V; I get 1.1mA at 100Hz, which is still orders of magnitude off. \$\endgroup\$
    – John M.
    Commented Sep 30, 2015 at 16:48

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