Hello,
reading the newsgroup, I am quite confusing about the use of VBAT/RTC.
I'am using an Embeddedartists LPC2138 board and when I power down this
board, just leaving the VBAT connected to a cell coin (3V) to keep
running the RTC, my board goes to a strange state with the reset led
on and random characters on the console. Do I need to setup something
specific more than to say that the RTC is running from the external
crystal?
My second concern is for my design. I need to keep the RTC during the
power loss (could be days). Is it a good idea to use the internal RTC
of the LPC with a battery (which one ?) or do I need to use an
external RTC with very low power consumption (which one also)?
Thanks for your help,
Best regards,
Christophe.
VBat and RTC
Started by ●December 15, 2006
Reply by ●December 15, 20062006-12-15
--- In l..., "Christophe"
wrote:
>
> Hello,
>
> reading the newsgroup, I am quite confusing about the use of
VBAT/RTC.
> I'am using an Embeddedartists LPC2138 board and when I power down
this
> board, just leaving the VBAT connected to a cell coin (3V) to keep
> running the RTC, my board goes to a strange state with the reset led
> on and random characters on the console. Do I need to setup
something
> specific more than to say that the RTC is running from the external
> crystal?
>
> My second concern is for my design. I need to keep the RTC during
the
> power loss (could be days). Is it a good idea to use the internal
RTC
> of the LPC with a battery (which one ?) or do I need to use an
> external RTC with very low power consumption (which one also)?
>
> Thanks for your help,
> Best regards,
> Christophe.
>
We tried the same thing with LPC2148 and could never get the current
below 45 uA. Too much for a small battery. Check out DS3232 from
Dallas/Maxim. It is a real time clock, thermometer and 236 bytes of
battery backed SRAM, really useful if you need to store some
parameters frequently. Dwaws about 3 uA from the battery. Interface
is I2C. We have it implemented now; no problems encountered.
Lars Marmsater
wrote:
>
> Hello,
>
> reading the newsgroup, I am quite confusing about the use of
VBAT/RTC.
> I'am using an Embeddedartists LPC2138 board and when I power down
this
> board, just leaving the VBAT connected to a cell coin (3V) to keep
> running the RTC, my board goes to a strange state with the reset led
> on and random characters on the console. Do I need to setup
something
> specific more than to say that the RTC is running from the external
> crystal?
>
> My second concern is for my design. I need to keep the RTC during
the
> power loss (could be days). Is it a good idea to use the internal
RTC
> of the LPC with a battery (which one ?) or do I need to use an
> external RTC with very low power consumption (which one also)?
>
> Thanks for your help,
> Best regards,
> Christophe.
>
We tried the same thing with LPC2148 and could never get the current
below 45 uA. Too much for a small battery. Check out DS3232 from
Dallas/Maxim. It is a real time clock, thermometer and 236 bytes of
battery backed SRAM, really useful if you need to store some
parameters frequently. Dwaws about 3 uA from the battery. Interface
is I2C. We have it implemented now; no problems encountered.
Lars Marmsater
Reply by ●December 15, 20062006-12-15
In my opinion it's better to use an external RTC like PCF8583. You
will need a battery switcher (like TPS3600) to supply the external
RTC.
Gabi
--- In l..., "Christophe"
wrote:
>
> Hello,
>
> reading the newsgroup, I am quite confusing about the use of
VBAT/RTC.
> I'am using an Embeddedartists LPC2138 board and when I power down
this
> board, just leaving the VBAT connected to a cell coin (3V) to keep
> running the RTC, my board goes to a strange state with the reset led
> on and random characters on the console. Do I need to setup
something
> specific more than to say that the RTC is running from the external
> crystal?
>
> My second concern is for my design. I need to keep the RTC during
the
> power loss (could be days). Is it a good idea to use the internal
RTC
> of the LPC with a battery (which one ?) or do I need to use an
> external RTC with very low power consumption (which one also)?
>
> Thanks for your help,
> Best regards,
> Christophe.
>
will need a battery switcher (like TPS3600) to supply the external
RTC.
Gabi
--- In l..., "Christophe"
wrote:
>
> Hello,
>
> reading the newsgroup, I am quite confusing about the use of
VBAT/RTC.
> I'am using an Embeddedartists LPC2138 board and when I power down
this
> board, just leaving the VBAT connected to a cell coin (3V) to keep
> running the RTC, my board goes to a strange state with the reset led
> on and random characters on the console. Do I need to setup
something
> specific more than to say that the RTC is running from the external
> crystal?
>
> My second concern is for my design. I need to keep the RTC during
the
> power loss (could be days). Is it a good idea to use the internal
RTC
> of the LPC with a battery (which one ?) or do I need to use an
> external RTC with very low power consumption (which one also)?
>
> Thanks for your help,
> Best regards,
> Christophe.
>
Reply by ●December 20, 20062006-12-20
You have to turn off the RTC in the power control
register. Running from an external crystal without
turing off you will draw about 230ma. With it turned
off, it is about 12uA. I also had strange problems
when the battery was dead. Data abort errors and
constant RTC interrupts. You should power the RTC
from the battery when off and from the 3.3V when power
is on.
--- l_marmsater wrote:
> --- In l..., "Christophe"
> wrote:
> >
> > Hello,
> >
> > reading the newsgroup, I am quite confusing about
> the use of
> VBAT/RTC.
> > I'am using an Embeddedartists LPC2138 board and
> when I power down
> this
> > board, just leaving the VBAT connected to a cell
> coin (3V) to keep
> > running the RTC, my board goes to a strange state
> with the reset led
> > on and random characters on the console. Do I need
> to setup
> something
> > specific more than to say that the RTC is running
> from the external
> > crystal?
> >
> > My second concern is for my design. I need to keep
> the RTC during
> the
> > power loss (could be days). Is it a good idea to
> use the internal
> RTC
> > of the LPC with a battery (which one ?) or do I
> need to use an
> > external RTC with very low power consumption
> (which one also)?
> >
> > Thanks for your help,
> > Best regards,
> > Christophe.
> >
> We tried the same thing with LPC2148 and could never
> get the current
> below 45 uA. Too much for a small battery. Check out
> DS3232 from
> Dallas/Maxim. It is a real time clock, thermometer
> and 236 bytes of
> battery backed SRAM, really useful if you need to
> store some
> parameters frequently. Dwaws about 3 uA from the
> battery. Interface
> is I2C. We have it implemented now; no problems
> encountered.
> Lars Marmsater
__________________________________________________
register. Running from an external crystal without
turing off you will draw about 230ma. With it turned
off, it is about 12uA. I also had strange problems
when the battery was dead. Data abort errors and
constant RTC interrupts. You should power the RTC
from the battery when off and from the 3.3V when power
is on.
--- l_marmsater wrote:
> --- In l..., "Christophe"
> wrote:
> >
> > Hello,
> >
> > reading the newsgroup, I am quite confusing about
> the use of
> VBAT/RTC.
> > I'am using an Embeddedartists LPC2138 board and
> when I power down
> this
> > board, just leaving the VBAT connected to a cell
> coin (3V) to keep
> > running the RTC, my board goes to a strange state
> with the reset led
> > on and random characters on the console. Do I need
> to setup
> something
> > specific more than to say that the RTC is running
> from the external
> > crystal?
> >
> > My second concern is for my design. I need to keep
> the RTC during
> the
> > power loss (could be days). Is it a good idea to
> use the internal
> RTC
> > of the LPC with a battery (which one ?) or do I
> need to use an
> > external RTC with very low power consumption
> (which one also)?
> >
> > Thanks for your help,
> > Best regards,
> > Christophe.
> >
> We tried the same thing with LPC2148 and could never
> get the current
> below 45 uA. Too much for a small battery. Check out
> DS3232 from
> Dallas/Maxim. It is a real time clock, thermometer
> and 236 bytes of
> battery backed SRAM, really useful if you need to
> store some
> parameters frequently. Dwaws about 3 uA from the
> battery. Interface
> is I2C. We have it implemented now; no problems
> encountered.
> Lars Marmsater
__________________________________________________
Reply by ●December 31, 20062006-12-31
We had also used the internal rtc but due to higher power
consumption when the power fail, we have decided to use the external
RTC [philips PCF8563] with the button battery of 3V.
--- In l..., Mark Norton
wrote:
>
> You have to turn off the RTC in the power control
> register. Running from an external crystal without
> turing off you will draw about 230ma. With it turned
> off, it is about 12uA. I also had strange problems
> when the battery was dead. Data abort errors and
> constant RTC interrupts. You should power the RTC
> from the battery when off and from the 3.3V when power
> is on.
>
> --- l_marmsater wrote:
>
> > --- In l..., "Christophe"
> > wrote:
> > >
> > > Hello,
> > >
> > > reading the newsgroup, I am quite confusing about
> > the use of
> > VBAT/RTC.
> > > I'am using an Embeddedartists LPC2138 board and
> > when I power down
> > this
> > > board, just leaving the VBAT connected to a cell
> > coin (3V) to keep
> > > running the RTC, my board goes to a strange state
> > with the reset led
> > > on and random characters on the console. Do I need
> > to setup
> > something
> > > specific more than to say that the RTC is running
> > from the external
> > > crystal?
> > >
> > > My second concern is for my design. I need to keep
> > the RTC during
> > the
> > > power loss (could be days). Is it a good idea to
> > use the internal
> > RTC
> > > of the LPC with a battery (which one ?) or do I
> > need to use an
> > > external RTC with very low power consumption
> > (which one also)?
> > >
> > > Thanks for your help,
> > > Best regards,
> > > Christophe.
> > >
> > We tried the same thing with LPC2148 and could never
> > get the current
> > below 45 uA. Too much for a small battery. Check out
> > DS3232 from
> > Dallas/Maxim. It is a real time clock, thermometer
> > and 236 bytes of
> > battery backed SRAM, really useful if you need to
> > store some
> > parameters frequently. Dwaws about 3 uA from the
> > battery. Interface
> > is I2C. We have it implemented now; no problems
> > encountered.
> > Lars Marmsater
> >
> >
> __________________________________________________
consumption when the power fail, we have decided to use the external
RTC [philips PCF8563] with the button battery of 3V.
--- In l..., Mark Norton
wrote:
>
> You have to turn off the RTC in the power control
> register. Running from an external crystal without
> turing off you will draw about 230ma. With it turned
> off, it is about 12uA. I also had strange problems
> when the battery was dead. Data abort errors and
> constant RTC interrupts. You should power the RTC
> from the battery when off and from the 3.3V when power
> is on.
>
> --- l_marmsater wrote:
>
> > --- In l..., "Christophe"
> > wrote:
> > >
> > > Hello,
> > >
> > > reading the newsgroup, I am quite confusing about
> > the use of
> > VBAT/RTC.
> > > I'am using an Embeddedartists LPC2138 board and
> > when I power down
> > this
> > > board, just leaving the VBAT connected to a cell
> > coin (3V) to keep
> > > running the RTC, my board goes to a strange state
> > with the reset led
> > > on and random characters on the console. Do I need
> > to setup
> > something
> > > specific more than to say that the RTC is running
> > from the external
> > > crystal?
> > >
> > > My second concern is for my design. I need to keep
> > the RTC during
> > the
> > > power loss (could be days). Is it a good idea to
> > use the internal
> > RTC
> > > of the LPC with a battery (which one ?) or do I
> > need to use an
> > > external RTC with very low power consumption
> > (which one also)?
> > >
> > > Thanks for your help,
> > > Best regards,
> > > Christophe.
> > >
> > We tried the same thing with LPC2148 and could never
> > get the current
> > below 45 uA. Too much for a small battery. Check out
> > DS3232 from
> > Dallas/Maxim. It is a real time clock, thermometer
> > and 236 bytes of
> > battery backed SRAM, really useful if you need to
> > store some
> > parameters frequently. Dwaws about 3 uA from the
> > battery. Interface
> > is I2C. We have it implemented now; no problems
> > encountered.
> > Lars Marmsater
> >
> >
> __________________________________________________
Reply by ●December 31, 20062006-12-31
I would be very careful with I2C RTCs. I have made very bad experience
because the I2C protocol may stay anywhere when the power of the CPU
dissapears in the middle of a I2C access. The next powerup sequence may be
unpredictible.
I suggest you to use some RTC chip with a clear RESET possibility of the I2C
part.
Kurt
>From: "dosh_harshal"
>Reply-To: l...
>To: l...
>Subject: [lpc2000] Re: VBat and RTC
>Date: Sun, 31 Dec 2006 10:40:57 -0000
>
>We had also used the internal rtc but due to higher power
>consumption when the power fail, we have decided to use the external
>RTC [philips PCF8563] with the button battery of 3V.
>
>--- In l..., Mark Norton
>wrote:
> >
> > You have to turn off the RTC in the power control
> > register. Running from an external crystal without
> > turing off you will draw about 230ma. With it turned
> > off, it is about 12uA. I also had strange problems
> > when the battery was dead. Data abort errors and
> > constant RTC interrupts. You should power the RTC
> > from the battery when off and from the 3.3V when power
> > is on.
> >
> > --- l_marmsater wrote:
> >
> > > --- In l..., "Christophe"
> > > wrote:
> > > >
> > > > Hello,
> > > >
> > > > reading the newsgroup, I am quite confusing about
> > > the use of
> > > VBAT/RTC.
> > > > I'am using an Embeddedartists LPC2138 board and
> > > when I power down
> > > this
> > > > board, just leaving the VBAT connected to a cell
> > > coin (3V) to keep
> > > > running the RTC, my board goes to a strange state
> > > with the reset led
> > > > on and random characters on the console. Do I need
> > > to setup
> > > something
> > > > specific more than to say that the RTC is running
> > > from the external
> > > > crystal?
> > > >
> > > > My second concern is for my design. I need to keep
> > > the RTC during
> > > the
> > > > power loss (could be days). Is it a good idea to
> > > use the internal
> > > RTC
> > > > of the LPC with a battery (which one ?) or do I
> > > need to use an
> > > > external RTC with very low power consumption
> > > (which one also)?
> > > >
> > > > Thanks for your help,
> > > > Best regards,
> > > > Christophe.
> > > >
> > > We tried the same thing with LPC2148 and could never
> > > get the current
> > > below 45 uA. Too much for a small battery. Check out
> > > DS3232 from
> > > Dallas/Maxim. It is a real time clock, thermometer
> > > and 236 bytes of
> > > battery backed SRAM, really useful if you need to
> > > store some
> > > parameters frequently. Dwaws about 3 uA from the
> > > battery. Interface
> > > is I2C. We have it implemented now; no problems
> > > encountered.
> > > Lars Marmsater
> > >
> > >
> >
> >
> > __________________________________________________
> >
> >
because the I2C protocol may stay anywhere when the power of the CPU
dissapears in the middle of a I2C access. The next powerup sequence may be
unpredictible.
I suggest you to use some RTC chip with a clear RESET possibility of the I2C
part.
Kurt
>From: "dosh_harshal"
>Reply-To: l...
>To: l...
>Subject: [lpc2000] Re: VBat and RTC
>Date: Sun, 31 Dec 2006 10:40:57 -0000
>
>We had also used the internal rtc but due to higher power
>consumption when the power fail, we have decided to use the external
>RTC [philips PCF8563] with the button battery of 3V.
>
>--- In l..., Mark Norton
>wrote:
> >
> > You have to turn off the RTC in the power control
> > register. Running from an external crystal without
> > turing off you will draw about 230ma. With it turned
> > off, it is about 12uA. I also had strange problems
> > when the battery was dead. Data abort errors and
> > constant RTC interrupts. You should power the RTC
> > from the battery when off and from the 3.3V when power
> > is on.
> >
> > --- l_marmsater wrote:
> >
> > > --- In l..., "Christophe"
> > > wrote:
> > > >
> > > > Hello,
> > > >
> > > > reading the newsgroup, I am quite confusing about
> > > the use of
> > > VBAT/RTC.
> > > > I'am using an Embeddedartists LPC2138 board and
> > > when I power down
> > > this
> > > > board, just leaving the VBAT connected to a cell
> > > coin (3V) to keep
> > > > running the RTC, my board goes to a strange state
> > > with the reset led
> > > > on and random characters on the console. Do I need
> > > to setup
> > > something
> > > > specific more than to say that the RTC is running
> > > from the external
> > > > crystal?
> > > >
> > > > My second concern is for my design. I need to keep
> > > the RTC during
> > > the
> > > > power loss (could be days). Is it a good idea to
> > > use the internal
> > > RTC
> > > > of the LPC with a battery (which one ?) or do I
> > > need to use an
> > > > external RTC with very low power consumption
> > > (which one also)?
> > > >
> > > > Thanks for your help,
> > > > Best regards,
> > > > Christophe.
> > > >
> > > We tried the same thing with LPC2148 and could never
> > > get the current
> > > below 45 uA. Too much for a small battery. Check out
> > > DS3232 from
> > > Dallas/Maxim. It is a real time clock, thermometer
> > > and 236 bytes of
> > > battery backed SRAM, really useful if you need to
> > > store some
> > > parameters frequently. Dwaws about 3 uA from the
> > > battery. Interface
> > > is I2C. We have it implemented now; no problems
> > > encountered.
> > > Lars Marmsater
> > >
> > >
> >
> >
> > __________________________________________________
> >
> >
