U4256BM Datasheet, PDF(2/14 Page) TEMIC Semiconductors – Frequency Synthesizer for Radio Tuning

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U4256BM Datasheet, PDF (2/14 Pages) TEMIC Semiconductors – Frequency Synthesizer for Radio Tuning

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U4256BM

Pin Description

PDO 1

20 GNDan

PD 2

DAC1 3

19 FMOSCIN

18 EN

DAC2 4

17 CLK

DAC3 5

VS 6

U4256BM

16 DATA

15 MX2LO

SWO1 7

SWO2 8

14 V5

13 OSCIN

SWO3 9

12 OSCOUT

SWO4 10

11 GND

96 11944

Figure 2. Pinning

Pin Symbol

Function

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 1

PDO Analog output

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 2

PD Current output

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 3

DAC1 Output 1,

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ digital to analog converter

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 4

DAC2 Output 2,

digital to analog converter

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 5

DAC3 Output 3,

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ digital to analog converter

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 6

VS Supply voltage analog part

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 7

SWO1 Switching output 1

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 8

SWO2 Switching output 2

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 9

SWO3 Switching output 3

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 10 SWO4 Switching output 4

GND Ground, digital part

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 12 OSCOUT Oscillator output

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 13 OSCIN Oscillator input

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 14

V5 Capacitor band gap

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 15 MX2LO Oscillator buffer output

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 16 DATA Data input

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 17

CLK Clock

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 18

EN Enable

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 19 FMOSCIN FM-oscillator input

ÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃÃ 20 GNDan Ground, analog part

Circuit Description

The U4256BM is a single chip PLL circuit, designed for

AM/FM RDS (Radio Data System) applications. The

special design allows to build automatic alignment tuner

systems. Two programmable DACs (Digital to Analog

Converter) support the computer controlled alignment.

The U4256BM has a very fast response time of maximum

800 ms (at 2 mA, fref = 100 kHz, measured on MPX

signal). It performs a high signal to noise ratio.

Only one supply voltage is necessary, due to a

integrated band gap.

The U4256BM is controlled via 3-wire bus.

Functional Description

The U4256BM is especially designed for AM up/down

converter systems, together with the tuner U4255BM.

Due to the integrated DACs, an automatic tuner

alignment is possible. All the functions of the U4256BM

can be software controlled via a serial 3-wire bus,

consisting of Enable, Clock and Data. The format and

procedure for the data transfer from the microcontroller

is shown in figures 3, 4 and table Data Transfer. All

requested data have to be transferred via 16-bit or 24-bit

commands. Due to the 8-bit structure, the serial output

interface of a microcontroller can be used for the data

transfer. The PLL functions can be controlled by 24-bit

commands, while the alignment functions are controlled

by 16-bit commands. The alignment function control

normally is set once by switching on the tuner. Then the

tuner automatically will be aligned. The data for

alignment are stored in a separate EPROM. Via integrated

capacitors it is possible to tune the reference oscillator

(this function is controlled via the 3-wire bus).

2 (14)

Rev. A2, 03-Nov-98

Preliminary Information

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