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Topic: SD Card N-Channel MOSFET - Reduce power consumption? (Read 1 time) previous topic - next topic

AnitoLabs

Problem: I have connected the SD card to an N-Channel MOSFET,IRF540N, (Low-Side Switch) but the SD card module seems to be pulling around 0.9mA of current even when Vgs=0V (OFF STATE).  :smiley-confuse:

Can you suggest possible workaround on how to reduce the power consumption on the SD Module.

CrossRoads

Use P-channel MOSFET on the VCC pin instead. Bring all control lines low to avoid powering the card thru the control lines.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

fat16lib

An SD card draws less than 100 μA when sleeping.  If you remove power, you must reinitialize the card which can draw 20 ma for a large fraction of a second. 

You need to use a new version of SdFat to insure the card will sleep properly when idle.  The old version of SdFat in the standard SD.h library has a bug that may prevent low power sleep.

You may want to read articles by Edward Mallon on low power use of SD cards.  The Cave Logger can run for over six months on three AA batteries. 

AnitoLabs

Use P-channel MOSFET on the VCC pin instead. Bring all control lines low to avoid powering the card thru the control lines.
So i'll just need to pull the pin down (0V) to activate the P-CHannel MOSFET?
Also when the MOSFET is in OFF-STATE will there be leakage current?

You need to use a new version of SdFat to insure the card will sleep properly when idle.  The old version of SdFat in the standard SD.h library has a bug that may prevent low power sleep.
Does the new SDFat.h library automatically enters into sleep mode when idle or do I need call a specific function?

fat16lib

Quote
Does the new SDFat.h library automatically enters into sleep mode when idle or do I need call a specific function?
It's automatic.  After every SD access, new versions of SdFat will enable sleep mode.  

Almost all SD cards go to a deep sleep mode that draws under 100 μA.  Some have more than one stage of sleep and draw around 1.0 ma for maybe a second before deep sleep.

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