BCM3440 Datasheet, PDF (2/2 Pages) Broadcom Corporation. – DIRECT CONVERSION SATELLITE TUNER

BCM3440 OVERVIEW
TQFP-48
950-2150 MHz
RF in
AF AGC
LNA
IF AGC
0^o
90^o
PLL
16 MHz ref.
I
+ I out
- I out
Q
+ Q out
- Q out
The BCM3440 is a highly integrated CMOS tuner for the direct
broadcast satellite (DBS) market. It is designed to operate with
Broadcom's Advanced Modulation Receiver, the BCM4500, which
supports 8PSK modulation with turbo code FEC. The BCM3440 also
operates with the BCM4201 QPSK satellite receiver. It is designed to
support the full 1–45 Mbaud DVB operating range with support for 950
to 2150 MHz input frequencies.
The BCM3440 is based on a direct conversion architecture to reduce
external component count and increase performance. The chip has
integrated LNA, VCO and PLL and has both RF and IF AGCs. The
BCM3440 uses a single 16-MHz crystal that it shares with the
BCM4500 for reduced system cost.
The BCM3440 is a single-chip satellite tuner implemented in low-cost
CMOS technology. The tuner takes in a differential L-band signal from
standard consumer-grade LNB devices. An on-chip LNA is controlled
by an internal AGC to provide wide tuner dynamic range. A direct
conversion architecture is used to convert the L-band signal to in-phase
and quadrature baseband signals. The signals required for direct
conversion are all generated within the chip by a fully integrated PLL
and a quadrature LO generator. These signals are mixed with the L-band
input and then filtered by low-pass filters to remove the upper image
produced by the mixer. A variable gain amplifier is then used to adjust
the baseband signal levels before processing by the channel selection
filters to optimize noise performance and prevent distortion within the
filters. The channel select filters are digitally programmable 5th order
low-pass Butterworth filters. The filters are controlled with BCM3440
register writes through the I²C interface in 1 MHz steps from 2-MHz to
36-MHz. The device output is a buffered signal capable of driving a
1k ohm differential load 1 Vpp. An on-chip DC servo loop is included
to to correct DC offsets inherent in direct conversion mixers and to
minimize the offsets through the channel select filters and output
buffers.
The BCM93440 reference design is available to simplify testing and
design using the BCM3440. Schematics, Gerber files and test and
evaluation software are available.
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