Re: LPC2188 current?
- From: linnix <me@xxxxxxxxxxxxxxxxxx>
- Date: Tue, 8 Jan 2008 20:06:01 -0800 (PST)
On Jan 8, 5:35 pm, Eric Smith <e...@xxxxxxxxxxxx> wrote:
I asked about current consumption specs for the LPC2888.
I am not sure whether you are using the latest datasheet or the Users
You can find the data sheet on the NXP website or here:
The specification is there on page 28.
Thanks for pointing me at newer data on that site.
I downloaded both the datasheet and user manual from the NXP web site
a few days ago. The data sheet (LPC2880_LPC2888_2.pdf) is Rev. 02
dated 21 November 2006. The spec on page 26 is <tbd>.
It seems odd that lpc2000.com, which if I understand correctly is not
officially affiliated with NXP, has newer datasheets and user manuals
than the official NXP site!
In "stop mode", for which they give a typical Ibat spec of 17.7uA,
is the RAM kept alive? And can the GPIO interrupts wake it up from
What I'm concerned with is power dissipation in two specific states:
1) The product is "on", with something being displayed on an LCD module,
but with the CPU not running while waiting for the user to press any
button on a keypad.
2) The product is "off". Only a specific "ON" button needs to turn
Figure 10 shows a "start" switch connected to the START pin to turn
on the DC-DC converter. But when the power source is a single
alkaline cell, doesn't the DC-DC converter need to be on to keep the
internal SRAM alive? If so, I need a typical power spec for the
DC-DC converter(s) on but the CPU and all IO devices (other than GPIO)
halted. The closest thing I see to a spec for that is Idd with
32kHz active (which I don't need), 12MHz stopped, and DC-DC converter
supplying 1.8V. That spec is 200 uA, from which I assume that the
corresponding Ibat would be more than 400 uA at 0.9V (low end of
Only if the DC-DC up converter is 100%. Boosters are difficult to be
400 uA drain in a powered off state is far too much
for a portable consumer device, and probably too much for the "on but
idle" state as well.
Or will the RAM be kept alive by the DCDC_Vbat pin
Probably not, only the DC-DC converter is kept in standby. No power
to the processor.
, in which case the
17.7 uA typ Ibat spec is all I need to worry about? Except that if
I want to use that for the idle state, I need to contrive for any
button of the keypad to trip the START pin. Ugh. That would suggest
using a second low-power microcontroller just to handle the keypad.
I am dealing with the same issue with an AVR (which claims 20uA at
1.8V standby). What they don't tell you is that it takes over 200uA
at 5V standby. So, I need another 1.8V AVR to turn on the 5V AVR.
Unless I measured it wrong, I am getting my butts kicked for this.
Don't assume anything without written confirmations (in datasheets)
and verifications (measured results).