AN725
Rev. 0.1
27
6. General Power-Saving Tips
6.1. Pins
Placing any unused pins in analog mode using the PBSTD module (PBMDSEL.x = 0) disables the drivers and
weak pull-ups on the pin. The pin will float and consume little power.
For pins that are connected to external hardware, place the pins in analog mode if possible. If this is not possible,
place the pins in a natural state that will consume no power. For example, if a pin has an external pull-down
resistor, putting a ‘0’ in the latch will draw no current from the external pull-down.
If the system configuration allows it, disabling weak pull-ups on a port-by-port basis may also help reduce
unnecessary power consumption in the pins.
6.2. Peripherals
Before entering the low power mode, disable any unwanted peripherals. Stopping the clock to the peripheral may
disable the peripheral, but if the peripherals operate on a clock independent from the AHB or APB clocks, only the
peripheral registers will be disabled. Disabling the module explicitly (DCDCEN = 0 for the DCDC0 module, for
example) will ensure the module does not draw extra power in the low power mode.
6.3. Biases
In addition to peripherals, disable any unneeded bias sources in the device before entering the low power mode.
These biases draw current to provide voltage references inside the chip. One example of a bias is the 1.2/2.4 V
VREF0 module or the ADC internal 1.65 V voltage reference.
6.4. Clocks
External oscillators require a bias to start and maintain oscillation. If possible, switching to the internal oscillators
and stopping the external oscillator will reduce the power consumption. The internal precision oscillator also
requires extra current to operate. In most cases, switching the AHB and APB clock to the Low Power Oscillator
(LPOSC0) or RTC0 oscillator before entering the low power mode will result in the lowest power consumption.
The SiM3L1xx devices feature programmable clocks for each peripheral. When entering a low power mode,
disabling the clocks to any unused peripherals will reduce the system power consumption.
