Phillips ARM LPC3180, low power floating point processor

"steve" skrev i meddelandet news: snipped-for-privacy@i39g2000cwa.googlegroups.com...

Since it is in 90 nm, it is going to take some time to get a flash version! Didnt check the datasheet, but the 7,1 mA is probably the core power consumption without any peripherals (which is how things typically are specified) Correct me if I am wroing.

If it is executing from external memory, you are going to take a hit on the I/O power consumption.

As a comparision, the AT91R40008 will use about 10 mW at 13 Mhz when executing from the internal 256 kB SRAM which is a little bit higher

The ARM9 based SAM9261 uses 64 mA at 200 Mhz. A simple calculation (dont know how true it is) 64 mA/200 * 13 * 1,2V = 5 mW. The PLL would be turned off at 13 Mhz so it is probably a tiny bit lower. The SAM9261 has 160 kB internal RAM so you can run significant microcontroller applications internally

The 0,9V core operation seems to be quite useful. None of these chips has an FPU inside of course.

the original figure I reference

say peripherals on, cache off, text says .45 mA additional hit with cache on

I don't know either, generally the power curve is somewhat linear at the high end, but not linear all the way down at low speeds

The LPC3180 also has 64Kb of cache, on other embedded processors I have use (MPC5554) you can use cache for data/instructions if you turn off the caching, don't know if this is true for the 3180 (I don't think the cache would be useful anyway at low speeds)

yes, that was the most interesting feature, I could probably drop the speed down by 80% on some of my applications if I convert the integer math to single cycle float instructions, that is where the big power saving would come in for me(in addition to the reduction of coding time using float), the DMA would help too, sounds like I will get a eval board when they come out, should be very interesting

The link to the power numbers clearly stated "peripherals ON", and the

But you don't need to, as you would normally run from the caches mostly or on-chip SRAM (they are pretty large at 32+32+64 KBytes total). With caches on it is 7.55mA or 6.8mW.

You need to take static current into account, this is significant at such low frequencies. 13Mhz uses 9.9mA, 130Mhz uses 51.6mA. Ie. 1/10th of the frequency means 1/5th of the power! From this we can conclude the static current is 5.3mA (at 1.2V and presumably 85C).

The Atmel datasheet mentions 5.5mA static current at 85C, so the SAM9261 would use (64-5.5)/200*13+5.5= 9.3mA at 13Mhz. So without voltage scaling it is slightly better, with voltage scaling the Philips part wins.

The large static current means that it is inefficient to run for long periods at a low frequency unless you also use voltage scaling. At 1.2V and 130Mhz it is 0.48mW/Mhz, at 13Mhz it 0.91mW/Mhz. But with voltae scaling to 0.9V it becomes 0.49mW/Mhz.

Wilco

Checkout the blurb here on the lpc2800:

It can be powered by a single 1.5 volt battery!