U4256BM
Frequency Synthesizer for Radio Tuning
Description
The U4256BM is a single chip frequency synthesizer in
BICMOS technology. Together with the AM/FM IC
U4255BM, it performs a complete AM/FM car radio front
end, which is recommended also for RDS (Radio Data
System) applications. It is controlled by 3-wire bus and
contains also Digital to Analog Converters (DACs) for
automatic alignment of the AM/FM tuner.
Features
D
D
D
D
D
D
Reference oscillator up to 15 MHz (tuned)
Oscillator buffer output (for AM up/down conversion)
Two programmable 16-bit dividers
Fine-tuning steps: AM
≥
1 kHz, FM
≥
2 kHz
Fast response time due to integrated loop push-pull stage
D
Four programmable switching outputs (open drain)
D
Three DACs for software controlled tuner alignment
D
Low power consumption
D
High S/N ratio
D
Integrated band gap
necessary
3-wire bus (enable, clock and data; 3 V and 5 V micro-
controllers acceptable)
*
only one supply voltage
Block Diagram
SWO1 SWO2 SWO3 SWO4
7
Tuning
13
OSCIN
12
OSCOUT
15
8
9
10
Oscillator
R–
divider
Switching outputs
DAC3
3–bit
VRef
DAC2
5
DAC3
MX2LO
OSC
buffer
CLK
DATA
EN
17
16
18
4
DAC2
3W–
bus
interface
DAC1
3
DAC1
AM/FM
VRef
6
VS
PDO
1
FMOSCIN
19
FM–
preamp
N–
divider
Phase
detector
Band-gap
Current
sources
2
11
GND
96 11799
PD
20
GNDan
V5
14
Figure 1. Block diagram
Ordering Information
Extended Type Number
U4256BM-AFS
U4256BM-AFSG3
Package
SSO20
SSO20
Remarks
Taped and reeled
Rev. A2, 03-Nov-98
1 (14)
Preliminary Information
TEMIC [ TEMIC SEMICONDUCTORS ]
