CC2520_11 Datasheet, PDF (40/133 Pages) Texas Instruments – 2.4 GHZ IEEE 802.15.4/ZIGBEE RF TRANSCEIVER

CC2520 DATASHEET
2.4 GHZ IEEE 802.15.4/ZIGBEE® RF TRANSCEIVER
SWRS068 – DECEMBER 2007
12 Power Modes
CC2520 has three power modes as described below. In all these power modes the supply voltage is applied
to the circuit.
In Low Power Mode 2 (LPM2) the digital voltage regulator is turned off (VREG_EN=0) and no clocks are
running. No data is retained. All analog modules are in power down state.
In Low Power Mode 1 (LPM1) the digital voltage regulator is on (VREG_EN=1), but no clocks are running.
Data is retained. The power down signals to the analog modules are controlled by the digital part.
In Active mode the digital voltage regulator is on (VREG_EN=1) and the crystal oscillator clock is running.
The power down signals to the analog modules are controlled by the digital part.
12.1 Switching Between Power Modes
When the device has been in LPM2, all register content is lost. To bring the device up to active mode, a
reset is required or the device will be in an unknown state. The reset can be applied either by setting the
RESETn pin low, or issuing a reset instruction (SRES) over the SPI. It is recommended that the RESETn
method is used, because it will give a controlled start and automatic start of the crystal oscillator.
Before entering LPM2, it is strongly recommended that the device is reset. This way, the configuration will
always be the same when the power to the digital part is removed, and it is less likely that there will be
issues with current spikes or other side effects of the power being removed.
LPM2
Set VREG_EN=0
Set GPIO5=0
Set RESETn=1
Set VREG_EN=1
Wait until regulator
has stabilized.
Use a timeout.
Set RESETn=0
Set VREG_EN=1
SRES
Wait until regulator
has stabilized.
Use a timeout.
SXOSCON
SNOP
Set RESETn=0
Set CSn=1
SRES
Set RESETn=1
Set CSn=0
Set CSn=0
Wait until SO=1
Set CSn=1
LPM1
SXOSCOFF
(Radio must be idle)
Active mode
SXOSCON
SNOP
Set CSn=0 and
wait until SO=1
Set CSn=1
Figure 7: Procedures for switching between power modes.
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