SAMB11 - Should I be able to shut down by pulling CHIP_EN low?

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This may wind up being a "SAMB11 Xplained Pro" hardware question instead of a "SAMB11 module" question, but here goes:

 

In modeling some stuff we're doing on a custom board that involves powering off the SAMB11 at certain times (with an LP38693) on a SAMB11 Xplained Pro by switching its power off with a relay, I discovered that the chip seems to draw enough power through the peripherals I have connected to continue to run!  This is not an ideal situation, but I looked at the datasheet (such as it is) and it seemed like I should be able to get it to power off by holding CHIP_EN low.  Since nothing exposes CHIP_EN on that board explicitly, I soldered to the RST pad on the back (which is at 3.3V while everything is running), but pulling it to GND does not seem to shut the chip down. (I also tried accessing it via the nRESET pin on the SWD header, but I don't even see 3.3V there)

 

- does anyone know if CHIP_EN is actually exposed on the RST pad (on the back of the board, seems to be a set of JTAG related pads)?

- should pulling CHIP_EN to GND actually force the board to power down?  I can try soldering directly to pin 22 of the SAMB11 module and try again (though that looks pretty tricky).

 

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Last Edited: Mon. Nov 6, 2017 - 05:59 PM
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Most chips will do the same thing - it is due to the intrinsic diodes that are on just about every pin for ESD protection. You need to isolate the other connections to the chip or have them go to 0V.

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Kartman wrote:
Most chips will do the same thing - it is due to the intrinsic diodes that are on just about every pin for ESD protection. You need to isolate the other connections to the chip or have them go to 0V.

 

Sorry, I'm confused. You mean staying powered on is normal?  (yes, I wasn't shocked by it, just annoyed)  Or do you mean something about CHIP_EN, which was my actual question.  (I guess I should have phrased it better)

 

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I know nothing about the samb11, so i can’t comment on the chip select question.
If you remove the supply to the samb11 (or just about any other cmos chip) it can get phantom powered via the port pins if they have voltage applied.

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I have the same problem. When the SAMB11 is powered off while external power at the peripherals, the SAMB11 is still working. Even with a serial resistors in peripheral IO lines the chips keeps working.

I try to use the brownout functionality, but unfortunelately this seems not working well in this chip. The support of Atmel/Microchip cannot help me with this until now.

 

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How many milliamps does the chip need to work? Apply Ohms law and see how many milliamps you are supplying. Being powered via the ports is not peculiar to just the samb11 - i will happen with just about any cmos chip. Have circuitry to disconnect the pins or have the pins at logic 0 so no current can flow.

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Kartman wrote:
Most chips will do the same thing
 

Kartman wrote:
If you remove the supply to the samb11 (or just about any other cmos chip) it can get phantom powered via the port pins if they have voltage applied.
 

Kartman wrote:
Being powered via the ports is not peculiar to just the samb11 - it will happen with just about any cmos chip

 

Is the message getting through yet ... ?

This reply has been marked as the solution. 
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Just as a followup, holding Chip_Enable low (on my custom board) does, in fact, cause the chip to shut down.  I'm not sure why I couldn't get it to work on the Xplained pro board other than possibly a bad soldering job trying to connect to CE, and/or bad guesses where it could be found on the board.  (Schematics, anyone?  Sigh.)