lpc2387 wake up from power down problem

Started by "ger...@yahoo.gr [lpc2000]" October 6, 2014
Hi all,
I am facing a problem during wake up from power down via RTC interrupt.
Let me explain; my LPC uses a battery as power back up when external power supply is down. When it switches in PD mode I wake up the MCU via RTC interrupt to check the battery level via A/D and then go to PD again. I have no idea when but some times when it wakes up from RTC INT I see to the multimeter that the device consumes too much mAmps about 0.5A. When this happens the device is stacked and the only way to work again is either forced Reset or release the battery.
I have found the same phenomeno when wake up and not re-configure the PLL.
But the fisrt thing I do when the device wakes up is to re-configure the PLL.
Has any one any idea???

Thanks in Advance

Chris

An Engineer's Guide to the LPC2100 Series

Hi,
It looks as a known effect with semiconductors: both transistors in a cell are open at the same time.
It happens when power is growing too slow, and reset does not come, or low power and noise, or bad (old) chip design.

So don't expect good working device using power from externat power supply.

WBR
Vlad

----- Original Message -----
From: g...@yahoo.gr [lpc2000]
To: l...
Sent: Monday, October 06, 2014 5:21 PM
Subject: [lpc2000] lpc2387 wake up from power down problem

Hi all,
I am facing a problem during wake up from power down via RTC interrupt.
Let me explain; my LPC uses a battery as power back up when external power supply is down. When it switches in PD mode I wake up the MCU via RTC interrupt to check the battery level via A/D and then go to PD again. I have no idea when but some times when it wakes up from RTC INT I see to the multimeter that the device consumes too much mAmps about 0.5A. When this happens the device is stacked and the only way to work again is either forced Reset or release the battery.
I have found the same phenomeno when wake up and not re-configure the PLL.
But the fisrt thing I do when the device wakes up is to re-configure the PLL.

Has any one any idea???

Thanks in Advance

Chris
Hi

In my experience, PLLs were always a problem after any kind of power down
mode. Resetting of PLLs was never successful after a power down mode no
matter what you do. They always gave a weird clock. This might be a silicon
design issue (I might be wrong). Bypass the PLLs from very beginning if you
are not particular about the clock speed and everything will run smoothly
as expected. Do update with the result if this helps.

Rgds
Shashank

On Mon, Oct 6, 2014 at 8:33 PM, 'Vladimir Ljaschko' v...@germtec.de [lpc2000]
wrote:

> 
> Hi,
> It looks as a known effect with semiconductors: both transistors in a cell
> are open at the same time.
> It happens when power is growing too slow, and reset does not come, or low
> power and noise, or bad (old) chip design.
>
> So don't expect good working device using power from externat power
> supply.
>
> WBR
> Vlad
> ----- Original Message -----
> *From:* g...@yahoo.gr [lpc2000]
> *To:* l...
> *Sent:* Monday, October 06, 2014 5:21 PM
> *Subject:* [lpc2000] lpc2387 wake up from power down problem
>
> Hi all,
> I am facing a problem during wake up from power down via RTC interrupt.
> Let me explain; my LPC uses a battery as power back up when external power
> supply is down. When it switches in PD mode I wake up the MCU via RTC
> interrupt to check the battery level via A/D and then go to PD again. I
> have no idea when but some times when it wakes up from RTC INT I see to
> the multimeter that the device consumes too much mAmps about 0.5A. When
> this happens the device is stacked and the only way to work again is either
> forced Reset or release the battery.
> I have found the same phenomeno when wake up and not re-configure the PLL.
> But the fisrt thing I do when the device wakes up is to re-configure the
> PLL.
>
> Has any one any idea???
>
> Thanks in Advance
>
> Chris
>
>
>

--
Shashank Maheshwari
Power Down Solved!

After a long time of absence I found the sollution.
I realised that the revision of the mcu it was "B" I changed ut with a new one revision "D" and it works fine.
If anyone had similar problem check if the mcu is the last Revision.

Regards
Chris