i.MX7 SNVS power consumption

[stefano_biancon]

Hi,

AN5383 states a current consumption of 4301uA in SNVS mode while the stated power matches a current of 430uA (1419uW/3.3V). On the other side the datasheet states an expected current consumption of around 5uA in this mode.

What is the correct value?

Is there any current consumption increase when tampers are used?

Best,

Stefano

[stefano_biancon]

Hi Gusarambula,

thanks for the follow-up.

We made some measures on our own I still have some concerns on the result:

- the EVK comes with a jumper to GND pre-installed on the connector where GPIO from the SNVS domain are routed, all the GPIO are pulled to VDD_SNVS_1P8_CAP with 10k resistors. Measuring the current in this condition leads to the result you mentioned above while removing jumper and resistors reduces the current to few uA (compatible with the current reported in the DS).

- from the i.MX7 RM, sec. 3.1.4.2:

Tamper Detection is a special mechanism provided through a chip pin to signal when the device encounters unauthorized opening or tampering. When not in use, the Tamper Detection signal is pulled-down internally. In case of use, it should be connected to a Tamper Detection contact in a target system (Normally closed, pulled-up to the VDD_SNVS_IN). 

Those keepers are apparently not needed when Tamper detection is not implemented.

1. Do you know what would be the purpose of the 10kohm resistors in the EVK?

2. is there a way to estimate the impact in terms of current consumption of using the Tamper detection function given the total resistance of the Tamper mesh lines.

[gusarambula]

Hello Stefano Bianconi,

The 430uA value sounds plausible (albeit a bit high) and it was taken from an actual use case so the real value for SNVS mode current consumption should be closer to this than to the value from the Datasheet. I’ll double check the value on the Datasheet as it does sounds too low and to address the difference between both.

I’ll let you know when I have more information.

Regards,

[gusarambula]

Hello Stefano Bianconi,

The correct value should 430uA as you caculated.

As for the different between the App Note and Datasheet, the Datasheet shows only the current of the chip itself and the Application Note shoes the actual current on the boards. You can see VSNVS power rail does not only supply VDD_SNVS_IN pin but also other pull up etc.

I hope this helps!

Regards,