SI4022-A1-FT Silicon Laboratories Inc, SI4022-A1-FT Datasheet - Page 2

• Manufacturer Part Number: SI4022-A1-FT
• Description: IC TX FSK 915MHZ 3.8V 16-TSSOP
• Manufacturer: Silicon Laboratories Inc
• Type: ISM Band FSK Transmitterr

Specifications of SI4022-A1-FT

• Package / Case: 16-TSSOP
• Frequency: 868MHz, 915MHz
• Applications: ISM
• Modulation Or Protocol: FSK
• Data Rate - Maximum: 115.2kbps
• Power - Output: 6dBm
• Current - Transmitting: 24mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Voltage - Supply: 2.2 V ~ 3.8 V
• Operating Temperature: -40°C ~ 85°C
• Operating Frequency: 434 MHz to 915 MHz
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Operating Supply Voltage: 2.5 V, 3.3 V
• Supply Current: 24 mA
• Supply Voltage (max): 3.8 V
• Supply Voltage (min): 2.2 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Memory Size: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 336-1623-5

DETAILED FEATURE-LEVEL DESCRIPTION
The Si4022 FSK transmitter is designed to cover the unlicensed
frequency bands at 868, and 915 MHz. The device facilitates
compliance with FCC and ETSI requirements.
PLL
The programmable PLL synthesizer determines the operating
frequency, while preserving accuracy based on the on-chip
crystal-controlled reference oscillator. The PLL’s high resolution
allows the usage of multiple channels in any of the bands. The
FSK deviation is selectable (from 20 to 160 kHz with 20 kHz
increments) to accommodate various bandwidth, data rate and
crystal tolerance requirements, and it is also highly accurate
due to the direct closed-loop modulation of the PLL. The
transmitted digital data can be sent asynchronously through
the FSK pin or over the control interface using the appropriate
command.
The RF VCO in the PLL performs automatic calibration, which
requires only a few microseconds. To ensure proper operation
in the programmed frequency band, the RF VCO is automatically
calibrated upon activation of the synthesizer.
RF Power Amplifier (PA)
The power amplifier has an open-collector differential output
and can directly drive a loop antenna with a programmable output
power level. An automatic antenna tuning circuit is built in to
avoid costly trimming procedures and the so-called “hand
effect.”
Crystal Oscillator and Microcontroller Clock Output
The chip has a single-pin crystal oscillator circuit, which provides
a 10 MHz reference signal for the PLL. To reduce external parts
and simplify design, the crystal load capacitor is internal and
programmable. Guidelines for selecting the appropriate crystal
can be found later in this datasheet. The transmitter can supply
the clock signal for the microcontroller, so accurate timing is
possible without the need for a second crystal. In normal
operation it is divided from the reference 10 MHz. During sleep
mode a low frequency (typical 32 kHz) output clock signal can
be switched on.
When the microcontroller turns the crystal oscillator off by
clearing the appropriate bit using the Power Management
Command, the chip provides a certain number (default is 128)
of further clock pulses (“clock tail”) for the microcontroller to
let it go to idle or sleep mode.
Low Battery Voltage Detector
The low battery detector circuit monitors periodically (typ. 8 ms)
the supply voltage and generates an interrupt if it falls below a
programmable threshold level.
Wake-Up Timer
The wake-up timer has very low current consumption (4 μA max)
and can be programmed from 1 ms to several hours.
It calibrates itself to the crystal oscillator at every startup and
then at every 40 seconds with an accuracy of ±0.5%. When the
crystal oscillator is switched off, the calibration circuit switches
it back on only long enough for a quick calibration (a few
milliseconds) to facilitate accurate wake-up timing. The periodic
autocalibration feature can be turned off.
Event Handling
In order to minimize current consumption, the transmitter
supports the sleep mode. Switching between the various modes
is controlled by the appropriate bits in the Power Management
Command (page 11).
Si4022 generates an interrupt signal on several events (wake-
up timer timeout, low supply voltage detection, on-chip FIFO
almost empty). This signal can be used to wake up the
microcontroller, ef fectively reducing the period the
microcontroller has to be active. The cause of the interrupt can
be read out from the receiver by the microcontroller through the
SDO pin.
Interface and Controller
An SPI compatible serial interface lets the user select the
frequency band, center frequency of the synthesizer, and the
output power. Division ratio for the microcontroller clock, wake-
up timer period, and low supply voltage detector threshold are
also programmable. Any of these auxiliary functions can be
disabled when not needed. All parameters are set to default after
power-on; the programmed values are retained during sleep mode.
The interface supports the read-out of a status register, providing
detailed information about the status of the transmitter.
Si4022
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