SI4825-A10 Datasheet, PDF (11/21 Pages) Silicon Laboratories – BROADCAST MECHANICAL TUNING AM/FM/SW RADIO RECEIVER

4. Functional Description
AM
ANT
FM
ANT
AMI
RFGND
FMI
LNA
AGC
0/90
XTALI
2.0~3.6V _VDD
AFC
REG
XTAL
OSC
Si4825-A10
Si4^S8ⁱ⁴3⁸²0⁵/34
ADC
DSP
DAC
ADC
AOUT
ADC
CONTROL INTERFACE
TUNE1/2
BAND
Figure 2. Si4825 Functional Block Diagram
4.1. Overview
The Si4825 is the entry level mechanical-tuned digital
CMOS AM/FM/SW radio receiver IC that integrates the
complete receiver function from antenna input to audio
output. The Si4825 extends Silicon Laboratories multi-
band tuner family, and further increases the ease and
attractiveness of design radio reception to audio
devices through small size and board area, minimum
component count, and superior, proven performance.
The Si4825 requires a simple application circuit, and
removes any requirements for manually tuning
components during the manufacturing process.
Leveraging Silicon Laboratories' proven and patented
digital low intermediate frequency (low-IF) receiver
architecture, the Si4825 delivers desired RF
performance and interference rejection in AM, FM, and
SW bands. The high integration and complete system
production test simplifies design-in, increases system
quality, and improves manufacturability.
4.2. FM Receiver
The Si4825 integrates a low noise amplifier (LNA)
supporting the worldwide FM broadcast band (64 to
109 MHz) and the TV audio stations within the
frequency range in China area are also supported.
Pre-emphasis and de-emphasis is a technique used by
FM broadcasters to improve the signal-to-noise ratio of
FM receivers by reducing the effects of high frequency
interference and noise. When the FM signal is
transmitted, a pre-emphasis filter is applied to
accentuate the high audio frequencies. All FM receivers
incorporate a de-emphasis filter which attenuates high
frequencies to restore a flat frequency response. Two
time constants are used in various regions. The de-
emphasis time constant can be chosen to be 50 or
75 µs.
Rev. 1.0
11