SI4825-A10 Datasheet, PDF (12/21 Pages) Silicon Laboratories – BROADCAST MECHANICAL TUNING AM/FM/SW RADIO RECEIVER

Si4825-A10
4.3. AM Receiver
The highly integrated Si4825-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.
The Si4825 supports the worldwide AM band with five
sub-bands. One of the bands is a universal AM band
(AM4, 520–1730 kHz) supporting both 9 kHz and
10 kHz channel spaces for all regional AM standards of
the world. Similar to the FM receiver, the Si4825-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.
4.4. SW Receiver
The Si4825 supports 36 short wave (SW) band
receptions from 2.3 to 28.5 MHz, 18 of which are meter
wave band (Narrow), and the rest of the SW bands are
with wider frequency range that can be used in SW
radio with 1 or 2 SW bands. Si4825 supports extensive
short wave features such as minimal discrete
components and no factory adjustments. The Si4825
supports using the FM antenna to capture short wave
signals.
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 Si4825-A10 chip.
4.6. Band Select
The Si4825-A10 supports worldwide AM band with five
sub-bands, US/Europe/Japan/China FM band with five
sub-bands, and SW band with 36 sub-bands. For details
on band selection, refer to “AN738: Si4825/36-A
Antenna, Schematic, Layout, and Design Guidelines."
4.7. Volume Control
The Si4825 not only allows customers to use the
traditional PVR wheel volume control through an
external speaker amplifier, it also supports direct digital
volume control through pins 10 and pin 11 by using
volume up and down buttons. Refer to "AN738:
Si4825/36-A Antenna, Schematic, Layout, and Design
Guidelines."
4.8. Reset, Powerup, and Powerdown
Setting the RSTB pin low will disable analog and digital
circuitry, reset the registers to their default settings, and
disable the bus. Setting the RSTB pin high will bring the
device out of reset.
Figure 1 shows typical reset, startup, and shutdown
timings for the Si4825. RSTB must be held low
(asserted) during any power supply transitions and kept
asserted as specified in Figure 1 after the power
supplies are ramped up and stable. Failure to assert
RSTB as indicated here may cause the device to
malfunction and may result in permanent device
damage.
A powerdown mode is available to reduce power
consumption when the part is idle. Putting the device in
powerdown mode will disable analog and digital circuitry
while keeping the bus active.
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Rev. 1.0