Rev.1.0 8/11 Copyright © 2011 by Silicon Labo ratories Si4840/44-A10
Si4840/44-A10
BROADCAST ANALOG TUNING DIGITAL DISPLAY AM/FM/SW
RADIO RECEIVER
Features
Applications
Description
The Si4840/44 is the first analog-tuned digital-display digital CMOS AM/FM/SW
radio receiver IC that integrates the complete receiver function from antenna input
to audio output. Working with Host MCU (I2C-compatible 2-wire control interface),
frequencies, and stereo/mono information can be displayed on LCD, while the
analog-tune features are kept. Leveraging Silicon Laboratories' proven and
patented digital low intermediate frequency (low-IF) receiver architecture, the
Si4840/44 deliver superior RF performance and interference rejection. The
superior control algorithm integrated in Si4840/44 provides easy and reliable
control interface while eliminating all the manual tuned external components used
in traditional solution.
Functional Block Diagram
Worldwide FM band support
(64–109 MHz)
Worldwide AM band support
(504–1750 kHz)
SW band support (Si4844 only)
(2.3–28.5 MHz)
Selectable support for all AM/FM
regional bands
2-wire control interface
Mono/Stereo and valid station
indicator
Digital volume support
Bass/Treble support
Minimal BOM components with no
manual alignment
Excellent real-world performance
Automatic frequency control (AFC)
EN55020 compliant
Two AAA batteries with 2.0 to 3.6 V
supply voltage (T = 25 °C)
Wide range of ferrite loop sticks and
air loop antenna support
24-pin SSOP package
RoHS compliant
Table and portable radios
Stereos
Mini/micro systems
Boom boxes
Clock radios
Modules for consumer electronics
Entertainment systems
Toys, lamps, and any application
needing an AM/FM radio
Mini HiFi
iPhone docking
Si4830/34
ADC
ADC
DSP
DAC
DAC ROUT
LOUT
AFC
Si484x
RFGND LNA
AMI
AGC
REG
VDD1/2
2.0~3.6V XTAL
OSC
FMI 0/90
AM
ANT
FM
ANT
CONTROL INTERFACE
SCLK
SDIO
TUNE1/2
BANDXTALI
RST
ADC
IRQ
This product, its features, and/or its
architecture is covered by one or more of
the following patents, as well as other
patents, pending and issued, both
foreign and domestic: 7,127,217;
7,272,373; 7,272,375; 7,321,324;
7,355,476; 7,426,376; 7,471,940;
7,339,503; 7,339,504.
Ordering Information:
See page 20.
Pin Assignments
Si4840/44-A10 (SSOP)
NC
FMI
RFGND
AMI
BAND
TUNE2
TUNE1
IRQ
LNA_EN
NC
NC
NC RST
LOUT
ROUT
DBYP
VDD2
SCLK
SDIO
XTALO
XTALI
VDD1
GND
GND
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
Si4840/44-A10
2 Rev.1.0
Si4840/44-A10
Rev.1.0 3
TABLE OF CONTENTS
Section Page
1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2. Typical Application Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
3. Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
4. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
4.2. FM Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
4.3. AM Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
4.4. SW Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
4.5. Frequency Tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.6. Band Select . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
4.7. Bass and Treble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
4.8. Volume Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
4.9. Stereo Audio Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
4.10. Stereo DAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
4.11. Soft Mute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
4.12. Reference Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
4.13. Memorizing Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
4.14. Programming with Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
5. Commands and Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
6. Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
6.1. Si4840/44-A10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
7. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
8. Package Outline: Si4840/44-A10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
9. PCB Land Pattern: Si4840/44-A10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
10. Top Markings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
10.1. Si4840/44-A10 Top Mark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
11. Additional Reference Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Si4840/44-A10
4 Rev.1.0
1. Electrical Specifications
Table 1. Recommended Operating Conditions1,2
Parameter Symbol Test Condition Min Typ Max Unit
Supply Voltage3VDD 2—3.6V
Power Supply Powerup Rise Time VDDRISE 10 µs
Notes:
1. Typical values in the data sheet apply at VDD = 3.3 V and 25 °C unless otherwise stated.
2. All minimum and maximum specifications in the data sheet apply across the recommended operating conditions for
minimum VDD =2.7V.
3. Operation at minimum VDD is guaranteed by characterization when VDD voltage is ramped down to 2.0 V. Part
initialization may become unresponsive below 2.3 V.
Table 2. DC Characteristics
(VDD = 2.7 to 3.6 V, TA = –15 to 85 °C)
Parameter Symbol Test Condition Min Typ Max Unit
FM Mode
Supply Current1IFM —21.0— mA
Supply Current2IFM Low SNR level 21.5 mA
AM/SW Mode
Supply Current1IAM —17.0— mA
Supplies and Interface
VDD Powerdown
Current
IDDPD —10— µA
Notes:
1. Specifications are guaranteed by characterization.
2. LNA is automatically switched to higher current mode for optimum sensitivity in weak signal conditions.
Si4840/44-A10
Rev.1.0 5
Figure 1. Reset Timing
Table 3. Reset Timing Characteristics
(VDD = 2.7 to 3.6 V, TA = –15 to 85 °C)
Parameter Symbol Min Typ Max Unit
RST Pulse Width tSRST 100 µs
30%
tSRST
RST 70%
Si4840/44-A10
6 Rev.1.0
Table 4. 2-Wire Control Interface Characteristics1,2,3
(VDD = 2.7 to 3.6 V, TA= –15 to 85 °C)
Parameter Symbol Test Condition Min Typ Max Unit
SCLK Frequency fSCLK 0—400kHz
SCLK Low Time tLOW 1.3 µs
SCLK High Time tHIGH 0.6 µs
SCLK Input to SDIO Setup
(START)
tSU:STA 0.6 µs
SCLK Input to SDIO Hold
(START)
tHD:STA 0.6 µs
SDIO Input to SCLK Setup tSU:DAT 100 ns
SDIO Input to SCLK Hold4,5 tHD:DAT 0—900ns
SCLK input to SDIO Setup
(STOP)
tSU:STO 0.6 µs
STOP to START Time tBUF 1.3 µs
SDIO Output Fall Time tf:OUT —250ns
SDIO Input, SCLK Rise/Fall Time tf:IN
tr:IN
—300ns
SCLK, SDIO Capacitive Loading Cb——50pF
Input Filter Pulse Suppression tSP 50 ns
Notes:
1. When VD= 0 V, SCLK and SDIO are low impedance.
2. When selecting 2-wire mode, the user must ensure that a 2-wire start condition (falling edge of SDIO while SCLK is
high) does not occur within 300 ns before the rising edge of RST.
3. When selecting 2-wire mode, the user must ensure that SCLK is high during the rising edge of RST, and stays high
until after the first start condition.
4. The Si484x delays SDIO by a minimum of 300 ns from the VIH threshold of SCLK to comply with the minimum tHD:DAT
specification.
5. The maximum tHD:DAT has only to be met when fSCLK = 400 kHz. At frequencies below 400 kHz, tHD:DAT may be
violated as long as all other timing parameters are met.
20 0.1 Cb
1pF
-----------
+
20 0.1 Cb
1pF
-----------
+
Si4840/44-A10
Rev.1.0 7
Figure 2. 2-Wire Control Interface Read and Write Timing Parameters
Figure 3. 2-Wire Control Interface Read and Write Timing Diagram
SCLK 70%
30%
SDIO 70%
30%
START STARTSTOP
tf:IN
tr:IN
tLOW tHIGH
tHD:STA
tSU:STA tSU:STO
tSP tBUF
tSU:DAT
tr:IN tHD:DAT tf:IN,
tf:OUT
SCLK
SDIO
START STOPADDRESS + R/W ACK DATA ACK DATA ACK
A6-A0,
R/W D7-D0 D7-D0
Si4840/44-A10
8 Rev.1.0
Table 5. FM Receiver Characteristics1,2
(VDD = 2.7 to 3.6 V, TA = –15 to 85 °C)
Parameter Symbol Test Condition Min Typ Max Unit
Input Frequency fRF 64 109 MHz
Sensitivity with Headphone
Network3
(S+N)/N = 26 dB 2.2 µV EMF
LNA Input Resistance4,5 —4— k
LNA Input Capacitance4,5 —5— pF
AM Suppression4,5,6,7 m = 0.3 50 dB
Input IP34,8 105 dBµV EMF
Adjacent Channel Selectivity4±200 kHz 50 dB
Alternate Channel Selectivity4±400 kHz 65 dB
Audio Output Voltage5,6,7,12 —80—mV
RMS
Audio Mono S/N5,6,7,9,10 —55— dB
Audio Stereo S/N3,4,5,7,9,10 —55— dB
Audio Frequency Response Low4–3 dB 30 Hz
Audio Frequency Response High4–3 dB 15 kHz
Audio Stereo Separation5,11 —40— dB
Audio THD5,6,11 —0.10.5 %
Audio Output Load Resistance4,10 RLSingle-ended 10 k
Audio Output Load Capacitance4,10 CLSingle-ended 50 pF
Powerup/Band Switch Time4——110ms
Notes:
1. Additional testing information is available in “AN603: Si4840/44 DEMO Board Test Procedure.” Volume = maximum
for all tests. Tested at RF = 98.1 MHz.
2. To ensure proper operation and receiver performance, follow the guidelines in “AN602: Si484x-A Antenna, Schematic,
Layout, and Design Guidelines.” Silicon Laboratories will evaluate schematics and layouts for qualified customers.
3. Frequency is 64~109 MHz.
4. Guaranteed by characterization.
5. VEMF =1 mV.
6. FMOD = 1 kHz, MONO, and L = R unless noted otherwise.
7. f = 22.5 kHz.
8. |f2 – f1| > 2 MHz, f0=2xf
1 – f2.
9. BAF = 300 Hz to 15 kHz, A-weighted.
10. At LOUT and ROUT pins.
11. f = 75 kHz.
12. Tested in Digital Volume Mode.
Si4840/44-A10
Rev.1.0 9
Table 6. AM/SW Receiver Characteristics1, 2
(VDD = 2.7 to 3.6 V, TA = –15 to 85 °C)
Parameter Symbol Test Condition Min Typ Max Unit
Input Frequency fRF Medium Wave (AM) 504 1750 kHz
Short Wave (SW) 2.3 28.5 MHz
Sensitivity3,4,5 (S+N)/N = 26 dB 30 µV EMF
Large Signal Voltage Handling5THD < 8% 300 mVRMS
Power Supply Rejection Ratio5VDD =100 mV
RMS, 100 Hz 40 dB
Audio Output Voltage3,6,8 — 60 mVRMS
Audio S/N3,4,6 — 55 dB
Audio THD3,6 — 0.1 0.5 %
Antenna Inductance5,7 180 450 µH
Powerup/Band Switch Time5From powerdown 110 ms
Notes:
1. Additional testing information is available in “AN603: Si4840/44 DEMO Board Test Procedure.” Volume = maximum
for all tests. Tested at RF = 520 kHz.
2. To ensure proper operation and receiver performance, follow the guidelines in “AN602: Si484x-A Antenna, Schematic,
Layout, and Design Guidelines.” Silicon Laboratories will evaluate schematics and layouts for qualified customers.
3. FMOD = 1 kHz, 30% modulation, 2 kHz channel filter.
4. BAF = 300 Hz to 15 kHz, A-weighted.
5. Guaranteed by characterization.
6. VIN =5mVrms.
7. Stray capacitance on antenna and board must be < 10 pF to achieve full tuning range at higher inductance levels.
8. Tested in Digital Volume Mode.
Table 7. Reference Clock and Crystal Characteristics
(VDD = 2.7 to 3.6 V, TA = –15 to 85 °C)
Parameter Symbol Test Condition Min Typ Max Unit
Reference Clo c k
XTALI Supported Reference Clock
Frequencies
32.768 kHz
Reference Clock Frequency
Tolerance for XTALI
–100 100 ppm
Crystal Oscillator
Crystal Oscillator Frequency 32.768 kHz
Crystal Frequency Tolerance –100 100 ppm
Board Capacitance ——3.5pF
Si4840/44-A10
10 Rev.1.0
Table 8. Thermal Conditions
Parameter Symbol Min Typ Max Unit
Thermal Resistance* JA —80°C/W
Ambient Temperature TA–15 25 85 °C
Junction Temperature TJ——92°C
*Note: Thermal resistance assumes a multi-layer PCB with the exposed pad soldered to a topside PCB pad.
Table 9. Absolute Maximum Ratings1,2
Parameter Symbol Value Unit
Supply Voltage VDD –0.5 to 5.8 V
Input Current3IIN 10 mA
Operating Temperature TOP –40 to 95 °C
Storage Temperature TSTG –55 to 150 °C
RF Input Level40.4 VPK
Notes:
1. Permanent device damage may occur if the above Absolute Maximum Ratings are exceeded. Functional operation
should be restricted to the conditions as specified in the operational sections of this data sheet. Exposure beyond
recommended operating conditions for extended periods may affect device reliability.
2. The Si4840/44-A10 devices are high-performance RF integrated circuits with certain pins having an ESD rating of
< 2 kV HBM. Handling and assembly of these devices should only be done at ESD-protected workstations.
3. For input pins RST, SDIO, SCLK, XTALO, XTALI, BAND, TUNE2, TUNE1, IRQ, and LNA_EN.
4. At RF input pins, FMI, and AMI.
Si4840/44-A10
Rev.1.0 11
2. Typical Application Schematic
Notes:
1. Place C4 close to VDD2 and DBYP pins.
2. All grounds connect directly to GND plane on PCB.
3. Pin 6 and 7 leave floating.
4. To ensure proper operation and receiver performance, follow the guidelines in “AN602: Si484x-A Antenna, Schematic,
Layout, and Design Guidelines.” Silicon Labs will evaluate the schematics and layouts for qualified customers.
5. Pin 8 connects to the FM antenna interface and pin 12 connects to the AM antenna interface.
6. Place Si484x as close as possible to antenna jack and keep the FMI and AMI traces as short as possible.
5
RFGND
Optional: AM air loop antenna
2.0 TO 3.6V
2.0 TO 3.6V
Optional
(Si4844 only)
2.5k/100M
FM
AM
BAND
Optional
To host MCU
To host MCU
Y1
32.768KHz
C2
22p
C3
22p
1
LNA_EN
2
IRQ
3
TUNE1
4
TUNE2
5
BAND
6
NC
7
NC
8
FMI
9
RFGND
10
NC
11
NC
12
AMI
13 GND
14 GND
15 RST
16 SDIO
17 SCLK
18 XTALO
19 XTALI
20 VDD1
21 VDD2
22 DBYP
23 ROUT
24 LOUT
U1
C5
0.47u
ANT1
AM antenna
ANT2
T1
C
0.47u
C4
0.1u
C1
0.1u
VR1
100k
B1
12
3
S1
R2
253k
R3
180k
R4
67k
IRQ
LNA_EN
FMI
LOUT
ROUT
AMI
AMI
VDD
VDD
BAND
TUNE1
TUNE1
SCLK
SDIO
RESET
Si4840/44-A10
12 Rev.1.0
3. Bill of Materials
Table 10. Si4840/44-A10 Bill of Materials
Component(s) Value/Description Supplier
C1 Reset capacitor 0.1 µF, ±20%, Z5U/X7R Murata
C4 Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R Murata
C5 Coupling capacitor, 0.47 µF, ±20%, Z5U/X7R Murata
B1 Ferrite bead 2.5 k/100 MHz Murata
VR1 Variable resistor (POT), 100 k, ±10% Kennon
U1 Si484x AM/FM/SW Analog Tune Digital Display Radio Tuner Silicon Laboratories
ANT1 Ferrite stick,180–450 μH Jiaxin
Optional Components
C2, C3 Crystal load capacitors, 22 pF, ±5%, COG
(Optional: for crystal oscillator option) Venkel
Y1 32.768 kHz crystal (Optional: for crystal oscillator option) Epson or equivalent
ANT2 Air loop antenna, 10-20 μHvarious
S1 Band switch Any, depends on customer
R2 Resistor, 253 k, ±1%, Venkel
R3 Resistor, 180 k, ±1% Venkel
R4 Resistor, 67 k, ±1% Venkel
Si4840/44-A10
Rev.1.0 13
4. Functional Description
Figure 4. Si4840/44-A10 Functional Block Diagram
4.1. Overview
The Si4840/44-A10 is the first analog-tuned digital-
display digital CMOS AM/FM/SW radio receiver IC that
integrates the complete receiver function from antenna
input to audio output. Working with an external MCU
with LCD/LED driver, Si4840/44-A10 can output the
AM/FM/SW frequencies, band, Bass/Treble and
stereo/mono information to display on LCD/LED, while
using a simple potentiometer at the front end for analog-
tune. Leveraging Silicon Laboratories' proven and
patented digital low intermediate frequency (low-IF)
receiver architecture, the Si4840/44 delivers superior
RF performance and interference rejection in AM, FM
and SW bands. Additionally, the digital core provides
advanced audio conditioning for all environments,
removing pops, clicks, and loud static in variable signal
conditions. The superior control algorithm integrated in
Si4840/44-A10 provides easy and reliable control
interface while eliminating all the manual tuned external
components used in traditional solutions.
Like other successful audio products from Silicon Labs,
Si4840/44-A10 offers unmatched integration and PCB
space savings with minimum external components and
small board area on a single side PCB. The high
integration and complete system production test
simplifies design-in, increases system quality, and
improves manufacturability. The receiver has very low
power consumption, runs off two AAA batteries, and
delivers the performance benefits of high performance
digital radio experience with digital display to the legacy
analog-tuned radio market.
The Si4840/44-A10 provides good flexibility in using the
chip. The frequency range of FM/AM/SW bands,
mono/stereo threshold, de-emphasis value, AM tuning
step, AM soft mute level/rate, and Bass/Treble can be
either configured by the MCU or by using external
hardware to make a selection. The reference clock of
the FM tuner can be either provided by the crystal, or by
the host MCU within tolerance.
Si4840/44-A10 also has flexibility in selecting bands
and configuring band properties, enabling masked Host
MCU for multiple projects, and reducing the cost of
development. Four tuning preferences are available to
meet different tuning preference requirements.
Si4840/44-A10
14 Rev.1.0
4.2. FM Receiver
The Si4840/44-A10 integrates a low noise amplifier
(LNA) supporting the worldwide FM broadcast band (64
to 109 MHz).
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. Refer to "AN602: Si484x-A Antenna, Schematic,
Layout, and Design Guidelines."
The Si4840/44-A10 also has advanced stereo blending
that employs adaptive noise suppression. As a signal
quality degrades, the Si4840/44-A10 gradually
combines the stereo left and right audio channels to a
mono audio signal to maintain optimum sound fidelity
under varying reception conditions. The Si4840/44-A10
can output a stereo signal to MCU with LCD/LED driver
to display on the LCD/LED so that the user can easily
discern the signal quality.
The stereo on signal is defined using both RSSI and the
Left and Right separation levels as these two
specifications are the primary factors for stereo
listening. The criteria can be set between two
conditions: the Left and Right channels are separated
by more than 6 dB with RSSI at >20 dB or Left and
Right channels are separated by more than 12 dB with
RSSI at >28 dB. The selection can be set up using
different values of the external resistor or configured by
the host MCU. Refer to "AN602: Si484x-A Antenna,
Schematic, Layout, and Design Guidelines." The user
can also refer to the “AN610: Si484x-A Programming
Guide” for those who want to configure the value by
host MCU.
4.3. AM Receiver
The highly integrated Si4840/44-A10 supports
worldwide AM band reception from 504 to 1750 kHz
with five sub-bands using a digital low-IF architecture
with a minimum number of external components and no
manual alignment required. This patented architecture
allows for high-precision filtering, offering excellent
selectivity and SNR with minimum variation across the
AM band. Similar to the FM receiver, the Si4840/44-A10
optimizes sensitivity and rejection of strong interferers,
allowing better reception of weak stations.
To offer maximum flexibility, the receiver supports a
wide range of ferrite loop sticks from 180–450 μH. An
air loop antenna is supported by using a transformer to
increase the effective inductance from the air loop.
Using a 1:5 turn ratio inductor, the inductance is
increased by 25 times and easily supports all typical AM
air loop antennas, which generally vary between 10 and
20 μH.
A 9, 10 kHz tuning step can be chosen by the external
resistor or host MCU according to the different regions,
and AM soft mute level can be programmed by the host
MCU to have different tuning experiences. Refer to
“AN610: Si484x-A Programming Guide” and "AN602:
Si484x-A Antenna, Schematic, Layout, and Design
Guidelines" for more details.
4.4. SW Receiver
The Si4844 supports short wave band receptions from
2.3 to 28.5 MHz in 5 kHz step size increments. Si4844
supports extensive short wave features such as minimal
discrete components and no factory adjustments. The
Si4844 supports using the FM antenna to capture short
wave signals. Refer to “AN610: Si484x-A Programming
Guide” and "AN602: Si484x-A Antenna, Schematic,
Layout, and Design Guidelines."for more details.
4.5. Frequency Tuning
A valid channel can be found by tuning the
potentiometer that is connected to the TUNE1 and
TUNE2 pin of the Si4840/44-A10 chip.
To offer easy tuning, the Si4840/44-A10 also outputs the
tuned information to the MCU with LCD/LED driver to
display. It will light up the icon on display if the RF signal
quality passes a certain threshold when tuned to a valid
station. Four tuning preferences are available. The user
can choose to have the best performance (volume,
stereo/mono effect) only at the exact channel, or the
best performance in a larger range. Refer to "AN610:
Si484x-A Programming Guide" for more details.
4.6. Band Select
The Si4840/44-A10 supports worldwide AM band with
five sub-bands, US/Europe/Japan/China FM band with
five sub-bands, and SW band with 16 sub-bands.
Si4840/44-A10 provides the flexibility to configure the
band and band properties at either the MCU side or the
Tuner side, enabling masked MCU for multiple projects.
For details on band selection, refer to "AN602: Si484x-A
Antenna, Schematic, Layout, and Design Guidelines"
and "AN610: Si484x-A Programming Guide".
Si4840/44-A10
Rev.1.0 15
4.7. Bass and Treble
The Si4840/44-A10 further supports Bass/Treble tone
control for superior sound quality. The Si4840/44-A10
can be set to be default normal, or programmed by the
host MCU I2C-compatible 2-wire mode. FM has nine
levels Bass/Treble effect and AM/SW has seven levels
Bass/Treble effect.For further configuration details, refer
to "AN610: Si484x-A Programming Guide."
4.8. Volume Control
The Si4840/44-A10 not only allows users to use the
traditional PVR wheel volume control through an
external speaker amplifier, it also supports digital
volume control programmed by the host MCU.
Si4840/44-A10 can be programmed to be Bass/Treble
mode only or digital volume mode only; it can also be
programmed to have the digital volume coexist with
Bass/Treble in two modes. Refer to "AN610: Si484x-A
Programming Guide" and "AN602: Si484x-A Antenna,
Schematic, Layout, and Design Guidelines" for more
details.
4.9. Stereo Audio Processing
The output of the FM demodulator is a stereo
multiplexed (MPX) signal. The MPX standard was
developed in 1961, and is used worldwide. Today's
MPX signal format consists of left + right (L+R) audio,
left – right (L–R) audio, a 19 kHz pilot tone.
Figure 5. MPX Signal Spectrum
4.9.1. Stereo Decoder
The Si4840/44-A10's integrated stereo decoder
automatically decodes the MPX signal using DSP
techniques. The 0 to 15 kHz (L+R) signal is the mono
output of the FM tuner. Stereo is generated from the
(L+R), (L–R), and a 19 kHz pilot tone. The pilot tone is
used as a reference to recover the (L–R) signal. Output
left and right channels are obtained by adding and
subtracting the (L+R) and (L–R) signals respectively.
4.9.2. Stereo-Mono Blending
Adaptive noise suppression is employed to gradually
combine the stereo left and right audio channels to a
mono (L+R) audio signal as the signal quality degrades
to maintain optimum sound fidelity under varying
reception conditions. Three metrics, received signal
strength indicator (RSSI), signal-to-noise ratio (SNR),
and multipath interference, are monitored
simultaneously in forcing a blend from stereo to mono.
The metric which reflects the minimum signal quality
takes precedence and the signal is blended
appropriately.
All three metrics have programmable stereo/mono
thresholds and attack/release rates. If a metric falls
below its mono threshold, the signal is blended from
stereo to full mono. If all metrics are above their
respective stereo thresholds, then no action is taken to
blend the signal. If a metric falls between its mono and
stereo thresholds, then the signal is blended to the level
proportional to the metric’s value between its mono and
stereo thresholds, with an associated attack and
release rate.
4.10. Stereo DAC
High-fidelity stereo digital-to-analog converters (DACs)
drive analog audio signals onto the LOUT and ROUT
pins. The audio output may be muted.
4.11. Soft Mute
The soft mute feature is available to attenuate the audio
outputs and minimize audible noise in very weak signal
conditions. Advanced algorithm is implemented to get a
better analog tuning experience. The soft mute feature
is triggered by the SNR metric. The SNR threshold for
activating soft mute is programmable, as are soft mute
attenuation levels and attack and decay rates.
4.12. Reference Clock
The Si4840/44-A10 supports RCLK input (to XTALI pin)
with the spec listed in Table 7. It can be shared with the
host MCU to save extra crystal.
An onboard crystal oscillator is available to generate the
32.768 kHz reference when an external crystal and
load capacitors are provided. Refer to "AN602: Si484x-
A Antenna, Schematic, Layout, and Design Guidelines"
for more details.
4.13. Memorizing Statu s
The Si4840/44-A10 provides the feature to memorize
status from the last power down with a simple design on
PCB, including frequency of the FM/AM/SW station.
Refer to "AN602: Si484x-A Antenna, Schematic,
Layout, and Design Guidelines" for details.
0575338231915
Frequency (kHz)
Modulation Le vel
Stereo Audio
Left - Right
RDS/
RBDS
Mono Audio
Left + Right Stereo
Pilot
Si4840/44-A10
Rev.1.0 16
4.14. Programming with Commands
To ease development time and offer maximum
customization, the Si484x provides a simple yet
powerful software interface to program the receiver. The
device is programmed using commands, arguments,
properties, and responses.
To perform an action, the user writes a command byte
and associated arguments, causing the chip to execute
the given command. Commands control an action such
as powerup the device, shut down the device, or get the
current tuned frequency. Arguments are specific to a
given command and are used to modify the command.
Properties are a special command argument used to
modify the default chip operation and are generally
configured immediately after powerup. Examples of
properties are de-emphasis level, RSSI seek threshold,
and soft mute attenuation threshold.
Responses provide the user information and are
echoed after a command and associated arguments are
issued. All commands provide a 1-byte status update,
indicating interrupt and clear-to-send status information.
For a detailed description of the commands and
properties for the Si484x, see "AN610: Si484x-A
Programming Guide".
Si4840/44-A10
Rev.1.0 17
5. Commands and Properties
Table 11. Si4840/44-A10 FM Receiver Command Summary
Cmd Name Description
0xE0 ATDD_GET_STATUS Get tune freq, band and etc status of the device
0xE1 ATDD_POWER_UP Power up device, band selection and band properties setup
0xE2 ATDD_AUDIO_MODE Audio output mode: get/set audio mode and settings
0x10 GET_REV Returns the revision information of the device.
0x11 POWER_DOWN Power down device.
0x12 SET_PROPERTY Sets the value of a property.
0x13 GET_PROPERTY Retrieve a property's value.
Note: The si4840/44 has its own power up and get status commands which is different from previous si47xx tuner parts. To
differentiate, we use “ATDD_POWER_UP” and ATDD_GET_STATUS to denote the ATDD specific commands instead
of the general si47xx “POWER_UP” and “STATUS” commands
Table 12. Si4840/44-A10 FM Receiver Property Summary
Prop Name Description Default
0x1100 FM_DEEMPHASIS Sets deemphasis time constant. Default is 75 μs. 0x0002
0x1300 FM_SOFT_MUTE_RATE Sets the attack and decay rates when entering and leaving
soft mute.
0x0040
0x1301 FM_SOFT_MUTE_SLOPE Configures attenuation slope during soft mute in dB attenua-
tion per dB SNR below the soft mute SNR threshold. Default
value is 2.
0x0002
0x1302 FM_SOFT_MUTE_
MAX_ATTENUATION
Sets maximum attenuation during soft mute (dB). Set to 0 to
disable soft mute. Default is 16 dB.
0x0010
0x1303 FM_SOFT_MUTE_
SNR_THRESHOLD
Sets SNR threshold to engage soft mute. Default is 4 dB. 0x0004
0x1207 FM_STEREO_IND
_BLEND_THRESHOLD
Sets the blend threshold for stereo indicator. Default value is
band dependent (either 0x9F or 0xB2)
0x9F
0xB2
0x1800 FM_BLEND_RSSI_
STEREO_THRESHOLD
Sets RSSI threshold for stereo blend. (Full stereo above
threshold, blend below threshold.) To force stereo, set this to
0. To force mono, set this to 127. Default value is 49 dBμV.
0x0031
0x1801 FM_BLEND_RSSI_
MONO_THRESHOLD
Sets RSSI threshold for mono blend (Full mono below
threshold, blend above threshold). To force stereo, set this to
0. To force mono, set this to 127. Default value is band
dependent (either 8 or 7).
0x0008
0x0007
0x4000 RX_VOLUME Sets the output volume. 0x003F
0x4001 RX_HARD_MUTE Mutes the audio output. L and R audio outputs may be
muted independently.
0x0000
0x4002 RX_BASS_TREBLE Sets the output bass/treble level 0x0004
0x4003 RX_ACTUAL_VOLUME Read the actual output volume 0x003F
Si4840/44-A10
18 Rev.1.0
Table 13. Si4840/44-A10 AM/SW Receiver Command Summary
Cmd Name Description
0xE0 ATDD_GET_STATUS Get tune freq, band and etc status of the device
0xE1 ATDD_POWER_UP Power up device, band selection and band properties setup
0xE2 ATDD_AUDIO_MODE Audio output mode: get/set audio mode settings.
0x10 GET_REV Returns the revision information of the device.
0x11 POWER_DOWN Power down device.
0x12 SET_PROPERTY Sets the value of a property.
0x13 GET_PROPERTY Retrieve a property's value.
Note: The si4840/44 has its own power up and get status commands which is different from previous si47xx tuner parts. To
differentiate, we use “ATDD_POWER_UP” and ATDD_GET_STATUS to denote the ATDD specific commands instead
of the general Si47xx “POWER_UP” and “STATUS” commands.
Table 14. Si4840/44-A10 AM/SW Receiver Property Summary
Prop Name Description Default
0x4000 RX_VOLUME Sets the output volume. 0x003F
0x4001 RX_HARD_MUTE Mutes the audio output. L and R audio outputs may be
muted independently.
0x0000
0x4002 RX_BASS_TREBLE Sets the output bass/treble level 0x0003
0x4003 RX_ACTUAL_VOLUME Read the actual output volume 0x003F
0x3300 AM_SOFT_MUTE_RATE Sets the attack and decay rates when entering and leaving
soft mute.
0x0040
0x3301 AM_SOFT_MUTE_SLOPE Configures attenuation slope during soft mute in dB attenu-
ation per dB SNR below the soft mute SNR threshold.
0x0002
0x3302 AM_SOFT_MUTE_
MAX_ATTENUATION
Sets maximum attenuation during soft mute (dB). Set to 0
to disable soft mute.
0x0010
0x3303 AM_SOFT_MUTE_
SNR_THRESHOLD
Sets SNR threshold to engage soft mute. 0x0008
Si4840/44-A10
Rev.1.0 19
6. Pin Descriptions
6.1. Si4840/44-A10
Pin Number(s) Name Description
1 LNA_EN Enabling SW external LNA
2 IRQ Interrupt Request
3 TUNE1 Frequency tuning
4 TUNE2 Frequency tuning
5 BAND Band selection and De-emphasis/Stereo separation selection
6,7 NC No connect. Leave floating.
8 FMI FM RF inputs. FMI should be connected to the antenna trace.
9 RFGND RF ground. Connect to ground plane on PCB.
10, 11 NC Unused. Tie these pins to GND.
12 AMI AM RF input. AMI should be connected to the AM antenna.
13, 14 GND Ground. Connect to ground plane on PCB.
15 /RST Device reset (active low) input
16 SDIO Serial data input/output
17 SCLK Serial clock input
18 XTALO Crystal oscillator output
19 XTALI Crystal oscillator input
20 VDD1 Supply voltage. May be connected directly to battery.
21 VDD2 Supply voltage. May be connected directly to battery.
22 DBYP Dedicated bypass for VDD
23 ROUT Right audio line output in analog output mode
24 LOUT Left audio line output in analog output mode
NC
FMI
RFGND
AMI
BAND
TUNE2
TUNE1
IRQ
LNA_EN
NC
NC
NC RST
LOUT
ROUT
DBYP
VDD2
SCLK
SDIO
XTALO
XTALI
VDD1
GND
GND
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
Si4840/44-A10
20 Rev.1.0
7. Ordering Guide
Part Number* Description Package Type Operating
Temperature/Voltage
Si4840-A10-GU AM/FM Broadcast Radio Receiver 24L SSOP Pb-free –15 to 85 °C
2.0 to 3.6 V
Si4844-A10-GU AM/FM/SW Broadcast Radio Receiver 24L SSOP Pb-free –15 to 85 °C
2.0 to 3.6 V
*Note: Add an “(R)” at the end of the device part number to denote tape and reel option. The devices will typically operate at
25 °C with degraded specifications for VDD voltage ramped down to 2.0 V.
Si4840/44-A10
Rev.1.0 21
8. Package Outline: Si4840/44-A10
The 24-pin SSOP illustrates the package details for the Si4840/44-A10. Table 15 lists the values for the dimensions
shown in the illustration.
Figure 6. 24-Pin SSOP
Table 15. Package Dimensions
Dimension Min Nom Max
A—1.75
A1 0.10 0.25
b0.200.30
c0.100.25
D 8.65 BSC
E 6.00 BSC
E1 3.90 BSC
e 0.635 BSC
L0.401.27
θ
aaa 0.20
bbb 0.18
ccc 0.10
ddd 0.10
Notes:
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.
3. This drawing conforms to the JEDEC Solid State Outline MO-137, Variation AE.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification
for Small Body Components.