current consumption in lpwfi mode

ben2 · ‎2007-01-12

Posted on January 12, 2007 at 13:57

ben2 · ‎2007-01-11

Posted on January 11, 2007 at 12:17

I am trying to get the current consumption down to below 1ma.

Has anyone here managed to do that in LPWFI mode ?

According to the datasheet the STR7 should take only 37ua in LPWFI mode but however much I try I can't get it below 1.5ma. Thats only slightly less than ST are quoting for SLOW mode.

Anyway I am doing all of the following before going into LPWFI mode.

NOTE this is on a practically bare PCB, with just voltage regulator, reset circuit, 32khz & 4Mhz osc.

switching to 32Khz osc and turning of main osc.

stop PLL

setting bottom 4 bits of PCU_RSTR to 1 as per datasheet

setting RCCU_PER bits as per datasheet.

disable all interrupts except XTI

clearing bits 2-5 in PCU_BOOTCR register. ( disable ADC , USB filters SPI0)

disable all peripheral clocks in APBn_CKDIS except( EIC & XTI)

it appears that leaving these enabled doesnt affect the current consumption .

Turn off Flash

set PVRWFI in PCU_PWRCR to enable LPWIFI mode

enter LPWIFI mode

current consuption is around 1.5ma

Where is all that current going ???

thanks

Ben

kaouther · ‎2007-01-11

Posted on January 12, 2007 at 07:09

You need to disable the PLL2 as well.

Are you measuring the current consumption of the chip only or on all the board?

which STR7x part number are you using? could you provide us the date code and all the marking on the chip package?

thanks.

ben2 · ‎2007-01-11

Posted on January 12, 2007 at 08:12

thanks for the reply.

As I wasn't using PLL2 I mistakenly thought it wouldn't be running.

After stopping it I am now getting around 70ua (total for board) in LPWFI mode.

thanks again.

kaouther · ‎2007-01-12

Posted on January 12, 2007 at 13:57

Good!This is the correct value expected for the current consumption on all the board.