Preliminary Data Sheet
6/30/09
BCM4325
Section 8: FM Receiver Subsystem
The BCM4325 includes a completely integrated FM radio receiver with RDS/RBDS, covering all FM bands from 76 MHz to
108 MHz. The receiver is controlled through commands on the BSC bus or the HCI. FM audio is available as stereo analog
output or in digital form through I2S or PCM. The FM subsystem can operate independently or in tandem with the Bluetooth
subsystem and can be powered up or down separately.
SENSITIVITY
The internal LNA has a noise figure (NF) of 6 dB, which helps achieve excellent sensitivity of –107 dBm, or 1 μV in 50Ω.
PLL TUNING
Clocks are locked to a reference clock or a 32.768 kHz external LPO, and no factory alignment is required.
DIGITAL FM OUTPUT
The FM radio audio is available digitally through the shared PCM and I2S pins and the sampling rate is nominally at 48 kHz.
The PCM interface runs off either the FM or the Bluetooth clock. The BCM4325 supports 3-wire I2S audio interface in either
master or slave configuration. The master or slave configuration is selected via HCI commands. In addition, multiple
sampling rates are supported, derived from either the FM or Bluetooth clocks.
ANALOG FM OUTPUT
The demodulated FM audio signal is available as line-level analog stereo output, generated by twin internal 16-bit DACs.
BROADCOM SERIAL CONTROL (BSC) BUS
The BCM4325 implements an I2C-compatible BSC slave bus interface to control the FM subsystem. The BSC bus interface
depends on the reference clock input being active. The interface supports a clock rate up to 400 kHz. The BSC slave address
is programmable using the UART HCI interface and requires a configuration download. The interface supports 7-bit
addressing mode and may require external pull-ups. Initial BSC communication has to be conducted at 100 kHz.
Broadcom Corporation
Document 4325-DS04-R
FM Receiver Subsystem
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