NRF51822-CEAC-R7 datasheet(26/130 Pages) NORDIC

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Page 26

nRF51822 Product Specification v3.3

3.4.2.2

System ON mode

In system ON mode the system is fully operational and the CPU and selected peripherals can be brought

into a state where they are functional and more or less responsive depending on the sub-power mode

selected.

There are two sub-power modes:

•Low power

• Constant latency

Low Power

In Low Power mode the automatic power management system is optimized to save power. This is done by

keeping as much as possible of the system powered down. The cost of this is that you will have varying CPU

wakeup latency and PPI task response.

The CPU wakeup latency will be affected by the startup time of the 1V7 regulator. The PPI task response will

vary depending on the resources required by the peripheral where the task originated.

The resources that could be involved are:

• 1V7 with the startup time t1V7

• 1V2 with the startup time t1V2

• One of the following clock sources

• RC16 with the startup time tSTART,RC16

• XO16M/XO32M with the startup time the clock management system tXO

Constant Latency

In Constant Latency mode the system is optimized for keeping the CPU latency and the PPI task response

constant and at a minimum. This is secured by forcing a set of base resources on while in sleep mode. The

cost is that the system will have higher power consumption.

The following resources are kept active while in sleep mode:

• 1V7 regulator with the standby current of I1V7

• 1V2 regulator. Here the current consumption is specified in combination with the clock

source.

• One of the following clock sources:

• RC16 with the standby current of I1V2RC16

• XO16M with the standby current of I1V2XO16

• XO32M with the standby current of I1V2XO32

1. For the clock source XO16M and XO32M we assume that the crystal is already running (standby). This will give an increase of the

power consumption in sleep mode given by ISTBY,X16M / ISTBY,X32M.

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