U4255BM-M Datasheet, PDF (3/32 Pages) ATMEL Corporation – AM / FM RECEIVER IC

U4255BM-M
Figure 2. Block Diagram
MX1OA
IF1FMI IF1AMI
V3 MX2OB
IF2IN
AMPLPF
MX1OB IF1REF
IF1OUT MX2IN
MX2OA
V3P
8
43 44 38 39 33
30 29 26 23 24
28 27
AMAGC ⁷
AMVREG ⁶
AGC
AM
FM
MX1AMA ⁴¹
AM
MX1AMB ³
V3
GNDMX ⁴
MX1FMB ²
FM
MX1FMA ¹
AGC
IF2OUT
20
AM
dem.
OPLPF
32
AGC
IFAGCL
36
IFAGCCH
35
Automatic
adjustment ₃₇ FILADJ
16
OSCOUT
Divider
GNDOSC ¹⁵
OSCE ¹⁴ OSC
OSCB ¹³
V3
Bus
Bandgap
17 18 19 5
12 25 42 9
EN DATA FMAGC GND METER
CLK
V57 VS
Adj.
chan
.
Multi-
path
Stop
FM
dem.
Soft
mute
11
MPX
22
MX2LO
10
ADJAC
INT
21 40
INT MULTIP
Dev.
ana.
34 31
SMUTE DEV
Functional
Description
Reception Mode
The U4255BM-M implements an AM up/down-conversion reception path from the RF
input signal to the AM-demodulated audio frequency output signal, and for FM reception
a double-conversion reception path from the RF input signal to the FM-demodulated
multiplex signal (MPX). A VCO and an LO prescaler for AM are integrated to generate
the LO frequency for the 1^st mixer. Automatic gain control (AGC) circuits are imple-
mented to control the preamplifier and IF stages in the AM and FM reception path.
For improved FM performance, an integrated IF filter with adjustable bandwidth, a soft-
mute feature and an automatic multipath noise cancellation (MNC) circuit are fully
integrated. A powerful set of sensors is provided for receiving condition analysis and
stop signal generation.
Several register bits (Bit 0 to Bit 93) are used to control circuit operation and to adapt
certain circuit parameters to the specific application. The control bits are organized in
two 8-bit and three 24-bit registers that can be programmed by the 3-wire bus protocol.
The bus protocol and the bit-to-register mapping is described in the section ’3-wire Bus
Description’. The meaning of the control bits is mentioned in the following sections.
The IC can be operated in four different modes. Mode AM, FM, WB, Standby are
selected by means of Bit 92 and Bit 93 according to Table 1.
In AM mode the AM mixer, the AM RF-AGC and the 1^st IF AM amplifier at Pin 33 are
activated. The input of the 2^nd IF amplifier is connected to Pin 28 and the output of the
2^nd IF amplifier is fed to the AM demodulator. The output of the AM demodulator is
available at MPX output Pin 11.
3
4519C–AUDR–07/02