I have design using Philips LPC2114 processor. Its battery driven so minimal power consumption is essential.
Problem is that even with cpu power down the circuit still uses about
2-3mA. :I I have measured that almost 2mA goes to CPU so something there is not right. I've read erratas and application notes and lots of other stuff and done the things they suggest to get power consumption down, but I can't get power consumption lower than that about 2mA.
Has anyone else have same kind of problems and maybe even solved them? And no, changing cpu is _not_ a option. ;)
If you have stopped the clock and made sure there is no load on some of the outputs of the MCU, there is one relatively new possibility. If the MCU is a new design or a new mask (I just don't know Philips processors), at 130nm and below geometries the leakage is pretty great, e.g. Motorolas MPC5200 specifies
52 mW with all clocks stopped - it is a pretty big chip, in other cases this would be a lot less but still far from the practically zero consumption at stopped clock we have been used to for decades.
What does the datasheet say about the power consumption in power down? Are you really in power down mode or perhaps in sleep mode. The difference could be whether the clock oscillator keeps on running or not. Also, if you have any I/O configured with pull-ups on (does the LPC support that?) while you have those inputs tied to ground, these will contribute to the power consumption too.
there is a fairly new Application Note on the Philips website here:
formatting link
10404.pdf
Although the title of the AN talks about initialization, have a look at chapter 4, "reducing power consumption". Ports 1,2,3 have internal pull-ups, always active, these pull-ups can add up to a noticeable current if they are externally pulled down during power down mode or if the software writes a "0" to the pins before it enters power down.
This would be my strongest suggestion, check pin level when entering power down and get as many as possible to high.
------- Cut and paste from the AN ------------
7=2E To reduce current consumption on the 3.3 V rail in power-down mode (let's consider the 144-pin devices): a=2E There are 80 pins with internal pull-ups on Ports 1, 2 and 3. These pull-ups are always active. b=2E Set those pins high or keep them floating before entering power down mode. If set low, they will consume around 50 =B5A (typical) on each pin. c=2E Port 0 does not have any internal pull-ups. These pins can be set low.
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