STR715 power down

ibc · ‎2007-07-03

Posted on July 03, 2007 at 12:15

STR715 power down

ibc · ‎2007-05-23

Posted on May 24, 2007 at 07:52

Hi,

We have developed a board using a STR715.

As it will run under battery in case of power failure, we have implemented the LPWFI mode (we also tried the STOP mode with the same result).

When waiting for an event, the board uses 900ÂµA. We expected 150ÂµA maximum (processor + regulator + MAX3243 + HC4060 used as oscillator).

Main oscillator (HC4060) is stopped, MAX3243 is powered down, regulator (LP2985 use 100ÂµA for 1mA load), flash powered down, MVR off, running from RTC (32768Hz)

Here is the code used to go into low power mode

// stop external oscillator (activates the RST input to stop the oscillator)

SetSHUTDOWN();

// deselect & reset PLL1

PRCCU_CFR&=0xFE;

PRCCU_PLL1CR&=0xFFFFFF7F;

PRCCU_PLL1CR|=0x7;

// deselect & reset PLL2 (strange as PLL2 is not provided in STR715 but 1.4mA less current when done)

PRCCU_PLL2CR&=0xFF7F;

PRCCU_PLL2CR|=0x7;

// select CKAF in LPWFI mode

PRCCU_CCR|=0x0002;

// select low power mode during WFI

PRCCU_CCR|=0x0001;

// stop flash during LPWFI mode

FLASH_CR0|=0x8000;

// disable MVR during LPWFI mode

PRCCU_PWRCR|=0x8000;

PRCCU_PWRCR|=0x0010;

PRCCU_PWRCR&=0x7FFF;

// activate LPWFI mode

PRCCU_SMR&=0xFFFE;

Any idea will be helpfull as it is very important to get the remaining 750ÂµA

Thanks for any answer

kaouther · ‎2007-05-31

Posted on June 01, 2007 at 07:09

Dear Marc,

Please make sure that you already selected the RTC clock prior switching off the oscillator using the SetSHUTDOWN() function?

Once you switch off the main oscillator no need to switch to CLk2 clock, you can switch to PLL Free running mode instead.

Could you test these steps;

- Switch to RTC clock,

- stop the main oscillator

To further reduce power consumption, it is required to clear some bits in the RCCU_PER register as recommended in the STR71x reference manual. And also disable PLL2 as done.

- select CKAF in LPWFI mode

- stop flash during LPWFI mode

- disable MVR during LPWFI mode

Could you test the Stop mode if you still have the same power consumption as in LPWFI mode?

Regards.

ibc · ‎2007-06-05

Posted on June 05, 2007 at 10:08

Hello,

Thanks for your answer.

This is exactly what I did.

In a few days I will have a new prototype board so I will make some more tests with this one.

In any case, I will retry also using the stop mode.

I will inform you with the results of the new board.

Regards.

ibc · ‎2007-07-03

Posted on July 03, 2007 at 12:15

Hello,

With our final pcb, everything seems to be ok since now the board needs only 110ÂµA in WFI mode. This value is the same for 99% of the production we tested until now.

There was a problem with the programming of the I/O pins and this problem draw 300ÂµA in excess.

The last ÂµA regained are due to the pcb and there is no explanation since the production is exactly the same as the prototype, except the prototype was soldered by hand.

Regards