MTK3339, sleep function?

[wormsmith]

I am considering ordering the MTK3339.
After reading the data sheet I see a diagram that includes a "sleep" and an "in office" mode but I do not see any instruction or data on how to put the device in this mode or what the power consumption is if this mode is achieved.
The only information provided is
Current Consumption 25mA acquisition, 20mA tracking
My device will sleep most of the time so I am looking for sleep current in the uA range.
The data sheet lists the VBACKUP as 7uA @3V, does this mean I can use a power switch to completely remove voltage from VCC and call that state the sleep mode?

Thanks

[adafruit]

not sure how that works, we've never used it in sleep mode but will look into it and update the tutorial
let us know if you figuer anything out!

[Stephanie]

According to the PMTK command manual (page 15), you can send it

Code: Select all

$PMTK161,0*28<CR><LF>

to put it to sleep, then send any byte to it to wake it back up again. Page 16 of the same manual lists a periodic mode that automatically alternates between sleep and active, letting you set the sleep and active times.

I don't see anything to indicate what the current consumption is when the device is asleep... I've ordered one that's in the mail right now but when I get it, I will be testing the sleep functions to see how they work & what the benefits are.

I couldn't find anything about 'office mode'.

Re. the VBACKUP, you are correct. According to the specsheet (page 13 & 16) if you disconnect VCC then it will draw 7uA at 3Vdc and allow rapid warm restarts when you apply power to VCC again.

Cheers!

[Stephanie]

I finally had a chance this morning to test the sleep function with the Ultimate GPS.

When you issue that $PMTK161,0*28 command, the GPS essentially turns itself 'off' - it appears to be almost as effective as disconnecting the power to the GPS. To wake it up again I'm sending a single byte (i'm using 32 - space character but it probably doesn't matter).

When the GPS is in 'sleep' mode the current draw on my project drops by over 20mA. I was reading an average of 36mA while the GPS was active, then after sending the sleep command the project dropped to 14mA.

Cheers!

[SadE]

So , I guess that with the sleep command it does not rely on the vbackup ?
Could you estimate the consumption of the MTK3339 itself please ?
You said it dropped by 20mA but in the normal condition of your project condition what is the current drawn by the MTK ?
I planned to use a P channel to control the MTK with a 3V lithium coin cell as Vbackup, but maybe it's not necessary anymore