SI4463 Datasheet, PDF (20/53 Pages) Silicon Laboratories – HIGH-PERFORMANCE

Si4463/61/60-C
Table 11. POR Timing
Variable
t_PORH
t_PORL
V_RRH
V_RRL
t_SR
Description
High time for VDD to fully settle POR circuit
Low time for VDD to enable POR
Voltage for successful POR
Starting Voltage for successful POR
Slew rate of VDD for successful POR
Min
Typ
10
10
90% x Vdd
0
Max Units
ms
ms
V
150 mV
1
ms
3.3.2. Shutdown State
The shutdown state is the lowest current consumption state of the device with nominally less than 30 nA of current
consumption. The shutdown state may be entered by driving the SDN pin (Pin 1) high. The SDN pin should be held
low in all states except the shutdown state. In the shutdown state, the contents of the registers are lost and there is
no SPI access. When coming out of the shutdown state a power on reset (POR) will be initiated along with the
internal calibrations. After the POR the POWER_UP command is required to initialize the radio. The SDN pin
needs to be held high for at least 10us before driving low again so that internal capacitors can discharge. Not
holding the SDN high for this period of time may cause the POR to be missed and the device to boot up incorrectly.
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.
3.3.3. Standby State
Standby state has the lowest current consumption with the exception of shutdown but has much faster response
time to RX or TX mode. In most cases standby should be used as the low power state. In this state the register
values are maintained with all other blocks disabled. The SPI is accessible during this mode but any SPI event,
including FIFO R/W, will enable an internal boot oscillator and automatically move the part to SPI active state. After
an SPI event the host will need to re-command the device back to standby through the “Change State” API
command to achieve the 40 nA current consumption. If an interrupt has occurred (i.e., the nIRQ pin = 0) the
interrupt registers must be read to achieve the minimum current consumption of this mode.
3.3.4. Sleep State
Sleep state is the same as standby state but the wake-up-timer and a 32 kHz clock source are enabled. The
source of the 32 kHz clock can either be an internal 32 kHz RC oscillator which is periodically calibrated or a
32 kHz oscillator using an external XTAL.The SPI is accessible during this mode but an SPI event will enable an
internal boot oscillator and automatically move the part to SPI active mode. After an SPI event the host will need to
re-command the device back to sleep. If an interrupt has occurred (i.e., the nIRQ pin = 0) the interrupt registers
must be read to achieve the minimum current consumption of this mode.
3.3.5. SPI Active State
In SPI active state the SPI and a boot up oscillator are enabled. After SPI transactions during either standby or
sleep the device will not automatically return to these states. A “Change State” API command will be required to
return to either the standby or sleep modes.
3.3.6. Ready State
Ready state is designed to give a fast transition time to TX or RX state with reasonable current consumption. In this
mode the Crystal oscillator remains enabled reducing the time required to switch to TX or RX mode by eliminating
the crystal start-up time.
3.3.7. TX State
The TX state may be entered from any of the state with the “Start TX” or “Change State” API commands. A built-in
sequencer takes care of all the actions required to transition between states from enabling the crystal oscillator to
ramping up the PA. The following sequence of events will occur automatically when going from standby to TX state.
1. Enable internal LDOs.
2. Start up crystal oscillator and wait until ready (controlled by an internal timer).
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Rev 1.0