SI4460-C2A-GM Datasheet, PDF (14/53 Pages) Silicon Laboratories – HIGH-PERFORMANCE, LOW-CURRENT TRANSCEIVER

Si4463/61/60-C
2. Functional Description
The Si446x devices are high-performance, low-current, wireless ISM transceivers that cover the sub-GHz bands.
The wide operating voltage range of 1.8–3.8 V and low current consumption make the Si446x an ideal solution for
battery powered applications. The Si446x operates as a time division duplexing (TDD) transceiver where the
device alternately transmits and receives data packets. The device uses a single-conversion mixer to downconvert
the 2/4-level FSK/GFSK or OOK modulated receive signal to a low IF frequency. Following a programmable gain
amplifier (PGA) the signal is converted to the digital domain by a high performance  ADC allowing filtering,
demodulation, slicing, and packet handling to be performed in the built-in DSP increasing the receiver’s
performance and flexibility versus analog based architectures. The demodulated signal is output to the system
MCU through a programmable GPIO or via the standard SPI bus by reading the 64-byte RX FIFO.
A single high precision local oscillator (LO) is used for both transmit and receive modes since the transmitter and
receiver do not operate at the same time. The LO is generated by an integrated VCO and  Fractional-N PLL
synthesizer. The synthesizer is designed to support configurable data rates from 100 bps to 1 Mbps. The
Si4463/61/60 operate in the frequency bands of 142–175, 283–350, 350–525, and 850–1050 MHz with a
maximum frequency accuracy step size of 28.6 Hz. The transmit FSK data is modulated directly into the  data
stream and can be shaped by a Gaussian low-pass filter to reduce unwanted spectral content.
The Si4463 contains a power amplifier (PA) that supports output power up to +20 dBm with very high efficiency,
consuming only 70 mA at 169 MHz and 85 mA at 915 MHz. The integrated +20 dBm power amplifier can also be
used to compensate for the reduced performance of a lower cost, lower performance antenna or antenna with size
constraints due to a small form-factor. Competing solutions require large and expensive external PAs to achieve
comparable performance. The Si4461 supplies output power up to +16 dBm. The Si4460 is designed to support
single coin cell operation with current consumption below 18 mA for +10 dBm output power. Two match topologies
are available for the Si4461 and Si4460, class-E and switched-current. Class-E matching provides optimal current
consumption, while switched-current matching demonstrates the best performance over varying battery voltage
and temperature with slightly higher current consumption. The PA is single-ended to allow for easy antenna
matching and low BOM cost. The PA incorporates automatic ramp-up and ramp-down control to reduce unwanted
spectral spreading. The Si446x family supports frequency hopping, TX/RX switch control, and antenna diversity
switch control to extend the link range and improve performance. Built-in antenna diversity and support for
frequency hopping can be used to further extend range and enhance performance. Antenna diversity is completely
integrated into the Si446x and can improve the system link budget by 8–10 dB, resulting in substantial range
increases under adverse environmental conditions. A highly configurable packet handler allows for autonomous
encoding/decoding of nearly any packet structure. Additional system features, such as an automatic wake-up
timer, low battery detector, 64 byte TX/RX FIFOs, and preamble detection, reduce overall current consumption and
allows for the use of lower-cost system MCUs. An integrated temperature sensor, power-on-reset (POR), and
GPIOs further reduce overall system cost and size. The Si446x is designed to work with an MCU, crystal, and a
few passive components to create a very low-cost system.
The application shown in Figure 1 is designed for a system with a TX/RX direct-tie configuration without the use of
a TX/RX switch. Most applications with output power less than 17 dBm will use this configuration. Figure 2
demonstrates an application for +20 dBm using an external T/R-switch.
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Rev 1.0