AP08056
Power Saving Features
Summary
Application Note
26
V1.0, 2006-12
9
Summary
•
Idle mode, slow-down mode and power-down mode are the three power saving
modes offered in the XC800 product family.
•
The combination of slow-down mode and idle mode may not necessarily consume
less power as compared to slow-down mode alone. It will depend on factors such as
the peripheral activities and the operating frequency.
•
One of main factors that affects the power consumption of a device is the system
frequency. Reducing the system frequency will reduce the power consumption of the
device.
•
Slow-down mode can be used to reduce the system frequency that is supplied to the
CPU and the peripherals thus reducing the power consumption of the devices.
However, flash programming and erasing operations are not guaranteed in slow-
down mode.
•
In PLL base mode, the system frequency can range between 5 MHz and 80 MHz
depending on the setting of CMCON.VCOSEL and the K factor. At the lower range,
the system frequency is very much reduced thus lowering the power consumption of
the device. The system frequency can be determined by outputting the system clock
signal on the CLKOUT pin. The base frequency is very sensitive to temperature and
therefore it could have an impact on the reliability on the system frequency. Flash
programming and erasing operations are not supported in this clock mode.
•
In prescaler mode, the system frequency is operating at half or equivalent of the
oscillator frequency depending on the K factor. Flash programming and erasing
operations are not supported in this clock mode.
•
Unused peripheral can be disabled by gating off it’s clock input to save power.
