M491B datasheet(10/16 Pages) STMICROELECTRONICS

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38MHz

38.8

40MHz

NORMAL AFC POSITION

TRANSMITTER

IDENTIFICATION

Pin 6

Pin 2

DIRECTION

SIGNALS

TDA4433

START

FAST UP

MEDIUM UP

S2 = 0.5 S1

MEDIUM DOWN

S3 = 0.25 S1

SLOW UP

S3 = 67Hz

38.8

VARICAP VOLTAGE

139.0MHz

38.8MHz

AFC

THESHOLD

DIGITAL

INFORMATION

STOP

RESPONSE

NORMAL AFC

OPERATION

38.8

MHz

Figure 10

PIN 14 : SWEEP SEARCH DISPLAY OUTPUT

This output, which is normally Low, goes High

during automatic search automatic preset et inter-

vals of 160ms for about 40ms to blank the LED of

band display.

BAND

LEDS

Figure 11

PIN 15 : VOLUME D/A OUTPUT

This output delivers a square wave signal of 7.8

kHz and duty cycle variable in 63 steps. In case of

a continuous command for varying the volume, the

duty cycle is changed at the rate of the transmitted

signal (approximately every 102ms with fref =

500kHz) or every 112ms if issued locally.

Overflow and underflow protection are provided.

The volume output can be switched to VSS and

reset to the previous level by means of the Mute

On/Off command. It is also reset by the Volume

Up/Down and the Mains On/Off commands.

The volume is muted for about 1s at each mains

on and off command during the power on reset time

and program change (0.5s).

At the first power on reset of VDD the volume D/A

is set at the level 21/64. The last level is preserved

until VDD is not removed.

M491B

10/16

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