Hello everyone,

This is my first post in this forum. For one of my projects, I am in need of a very low power consuming controller and I came across this device AT91R40008. Since it is a legacy device in Atmel's line card, I wont be using it for my project. But, when I was going through its datasheet, I found the following :

Mode : Normal
Conditions : Fetch in ARM mode from internal SRAM. All peripheral clocks activated
Power consumption : 0.83 mW / Mhz.

This will mean that the device will consume only 3.32 mW if I run it at 4MHz. This seems to be too low to be reasonable. I would like to know if this is the fact. Has anyone tried to measure the actual power consumption.

Also, the features of this AT91R40008 is awesome. I would like to know if there is a controller in actual production with similar features and comparable power consumptions.

Thanks for your time. Awaiting a reply.

BEAMer

One of your problems is that this looks at core power, most of the power in real system will be eaten at the external interfaces, where you have 4 or 8 mA buffers, and run at 3/3.3V

Want some low power ARM's, look at the Cortex M3 offerings. Some the lower power ones are about 230uA/MHz from FLASH, 190uA/MHz from RAM. In the lower KHZ range you're probably looking at the 10's uA, but you're not going to be able to do anything worth while.

A lot of these older ATMEL parts were deprecated because they had larger off-die flash memories. ie one package with a processor die, and a flash die. The flash die kept getting shrunk and keeping the part qualified was a tedious process.

What features do you actually need? Large internal single cycle SRAM, particular peripherals? Large Flash? What kind of horse power does your application need?

Historically I've use AT91FR4081 and AT91R40008 parts, but I wasn't running them at 4MHz and they had a lot of other circuitry around them.

More current ATMEL ARM9's with larger SRAM are the 9261 and 9263, but they too seem to be EOL, large/fast RAM is expensive.

Hello CptTitanic,

Thanks for that immediate and elaborate reply. It did put a few things in place.

My requirements are that the power consumption must be as low as possible. I am looking for something like 3mA consumption @ 4 MHz. For me, horsepower is not a major criteria but Flash is... I am looking for an on-chip Flash of about 512 KBytes. Internal SRAM is not an issue as I am planning to go for a low power external one. Other than that the usual UART, SPI, I2C and A/D should do.

If you have any controller in mind matching the above requirements, please let me know. It will be very helpful.

Also, one more question... Some datasheets specify the power consumption in terms of current / frequency (example : xx uA / MHz). So can we assume this relationship to be linear and calculate the power consumption for any frequency that the processor can run?

Thanks in advance!

BEAMer