LPC2188 current?

Hi Eric,

I am not sure whether you are using the latest datasheet or the Users Manual. You can find the data sheet on the NXP website or here:

The specification is there on page 28.

hth, Robert

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 .

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 that state?

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 it on.

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 battery range). 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, 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.

Thanks! Eric

Only if the DC-DC up converter is 100%. Boosters are difficult to be that high.

Probably not, only the DC-DC converter is kept in standby. No power to the processor.

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).

l> Only if the DC-DC up converter is 100%. Boosters are difficult to be

Hence my use of the phrase "more than".

Philips seems to be trying to push this part for battery-powered applications using a single alkaline cell, but if the DC-DC converter needs to run to keep the RAM alive, the actual standby current will be fairly high, and it will actually be a very poor choice for such applications.

Yes, I've been down that sort of path before too, which is why I'm asking the questions now rather than jumping right in.

There's so much extraneous crap on the commercially available LPC2888 boards that I don't think I could use them to test the power consumption.

Thanks, Eric

I believe that is the datasheets, in the figures in back

Yes, of course, the details are always in back pages. The graph says

4uA at 2V and 18uA at 5.5V, but I am getting much higher than that. The chip is in Power-down mode with everything off, except with pin change interrupt. I can't think of anything else other than conditionally dropping the standby voltage. The working battery voltage will be between 5.5V and 2V.

Ok, but you said standby, not power down initially, they have different meanings (the datasheet I'm looking at (169) has up to 180uA in standby). You doing something wrong if your in power down and getting that much current, don't know what though ;)