SI4455-B1A-FM Datasheet, PDF (26/40 Pages) Silicon Laboratories – EASY-TO-USE, LOW-CURRENT OOK/(G)FSK SUB-GHZ TRANSCEIVER

Si4455
TX = 19 mA
Tune = 100us@6.9 mA
Ready = 300 us@1.8 mA
Reg Inrush = 5 us@2 mA
Standby = 50 nA
Standby = 50 nA
Figure 13. Start-Up Timing and Current Consumption using Standby State
5.2.1. Shutdown State
The shutdown state is the lowest current consumption state of the device and is entered by driving SDN (Pin 2)
high. In this state, all register contents are lost and there is no SPI access. To exit this mode, drive SDN low. The
device will then initiate a power on reset (POR) along with internal calibrations. Once this POR period is complete,
the POWER_UP command is required to initialize the radio and the configuration can then be loaded into the
device. The SDN pin must be held high for at least 10 µs before driving it low again to insure the POR can be
executed correctly. The shutdown state can be used to fully reset the part. If POR timing and voltage requirements
cannot be met, it is highly recommended that SDN be controlled using the host processor rather than tying it to
GND on the board.
5.2.2. Standby State
The standby state has similar current consumption to the shutdown state but retains all register values, allowing for
a much faster response time. Because of these benefits, most applications will want to use standby mode rather
than shutdown. The standby state is entered by using the CHANGE_STATE API command. While in this state, the
SPI is accessible but any SPI event will automatically transition the chip to the SPI active state. After the SPI event,
the host will need to re-command the device to standby mode.
5.2.3. SPI Active State
The SPI active state enables the device to process any SPI events, such as API commands. In this state, the SPI
and boot up oscillator are enabled. The SPI active state is entered by using the CHANGE_STATE command or
automatically through an SPI event while in standby mode. If the SPI active state was entered automatically from
standby mode, a CHANGE_STATE command will be needed to return the device to standby mode.
5.2.4. Ready State
Ready state is designed to give a fast transition time to TX or RX state with minimized current consumption. In this
mode the crystal oscillator remains enabled to minimize the transition time. Ready state can be entered using the
CHANGE_STATE command.
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Rev 1.1