PDA

View Full Version : Power consumption reduction


johnsmithx
03-02-03, 09:01 PM
The manual states the following:

'The total draw for the IsoPod™ under maximum speed is approximately 200 mA.

Sleeping or slowing the processor can substantially reduce current consumption.

The TD0 signal can shut down the RS-232 converter, saving about 30 mA, when not used for transmission, if the receiving unit will not sense this as noise.

The TD1 signal can shut down the RS-485 transceiver, U4, saving about 10 mA, when not used for transmission, if the other RS-485 receiving units will not sense this as noise. The other RS-485 transceiver, U3, cannot be shut down, but can be left uninstalled by arrangement with the factory.

Each digital pin is capable of sinking 4 mA and sourcing –4 mA. Each LED draws 1.2 mA when lit.'

The use of sleep modes is easy enough to figure, what I was curious about, was clock speed reduction, and how this is implemented. For example:

'The 68HC11 provides high performance at low power with supply voltages ranging from 3 V to 5.5 V. Further power reductions can be achieved by some devices which have a Phase-Locked Loop (PLL) clock synthesizer circuit. The PLL allows clock speed reduction by switching the internal clock to a lower, power-saving frequency. '

Since the ISOPOD has ample power for any reasonable applications I can imagine, I was wondering if there is an equivalent simple method by which I may reduce the clock speed of the ISOPOD controller, and what kind of current draw reduction might be achieved by this?

Basically, if I strip out everything I can, how low will this thing go in terms of net source draw? Lowering consumption is more important to me than flat out performance.

Thanks.

nmitech
03-03-03, 11:22 AM
The followings are yielded ~80mA less, from a quick test on IsoPod V2,

Half speed cpu, ~ 35mA less
All leds off, ~ 40mA less
RS-232 shutdown, ~ 5mA less