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SiW1721B
60 0076 R00F SiW1721B Radio Modem IC DS
Description
The following figure shows the SiW1721B Radio Modem functional block diagram. During the receive process, the radio
signal is taken from the single-ended RF input pin that feeds into the low noise amplifier (LNA). The signal from the LNA is
directly down-converted to I/Q baseband, filtered with an anti-aliasing filter, and converted to a digital signal with a high
resolution analog-to-digital converter. The critical channel filtering is done in the digital domain for stable and repeatable
performance. The signal is then processed by a high performance GFSK demodulator. The IC has multiple internal self-
calibration circuits to maintain stable and repeatable performance from part-to-part as well as over the full temperature
range.
The IC has two fully integrated regulators: one for the radio (analog regulator) and one for the digital logic (digital
regulator). The digital regulator can be used to supply a Bluetooth baseband controller. Both regulators can be bypassed if
external regulation is desired.
Note:
When bypassing the analog regulator, the VBATT_ANA and VCC_OUT pins must be tied together and the external analog
voltage (1.8 V) should be applied to the VBATT_ANA pin. When bypassing the digital regulator, the VBATT_DIG pin should be
left unconnected and the external digital voltage (1.8 V) should be applied to the VBB_OUT pin.
The IC also provides power on reset and glitch-free clock start-up. A reference PLL can be enabled to support a number of
different reference frequencies.
Digital control functions and a programming interface provide radio modem control and a flexible interface to external
Bluetooth link controllers.
Radio Interface
An internal power control loop maintains a very stable RF_IO signal level over the full temperature range and from part to
part. This means predictable and repeatable range at any temperature.
Modem Interface
The modem interface transfers the Bluetooth data between the SiW1721B Radio Modem and the ASIC. For reference
purposes, the pin description table (Table 1) provides a brief description of typical interface modes.
Clock Signals
Multiple reference clock frequencies can be used as a reference for the RF circuits, to synthesize clocks for most of the
internal digital circuits, and to supply external processors with timing signals.
Serial Programming Interface (SPI)
The serial programming interface (SPI) is used to access the internal registers of the SiW1721B Radio Modem. The SPI is
a synchronous serial interface that can be clocked to a nominal speed of 8MHz.
Power
The SiW1721B Radio Modem includes both analog and digital voltage regulators. Input options are based on factors such
as voltage source, where internal regulators are used, and I/O voltage.
LNA
90
0
ADC
PLL
Synthesizer
90
0
RF_IO
GFSK
Modem
DAC
ADC
DAC
Internal
50-Ohm
Match
Network
TX_BIAS
IDAC
Register
File
System
Control
HOP_STROBE
TX_RX_SWITCH
RX_TX_DATA
CD_TXEN
Power
Control
ENABLE_RM
PLL
Control
Voltage Regulators and
Power Distribution
Clock Distribution
SPI_SS
SPI_TXD
SPI_RXD
SPI_CLK
Serial
Programming
Interface
(SPI)
SiW1721B Block Diagram
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