M491B Datasheet, PDF(7/16 Page) STMicroelectronics – SINGLE-CHIP VOLTAGE SYNTHESIS TUNING SYSTEM WITH 1 ANALOG CONTROL

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M491B Datasheet, PDF (7/16 Pages) STMicroelectronics – SINGLE-CHIP VOLTAGE SYNTHESIS TUNING SYSTEM WITH 1 ANALOG CONTROL

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Figure 6

M491B

D/A

Converter

Varicap

down-up

PIN 6 : DIGITAL AFT STATUS OUTPUT

(see Figure 7)

This output shows the status of the digital AFT. It is

low when the digital AFT is enabled and it can

directly drive a LED.

The output consists of an open drain transistor.

PINS 7 & 8 : OSCILLATOR INPUT/OUTPUT

(see Figure 8)

The frequency of the clock oscillator should be

between 445 and 510kHzusing a low-cost ceramic

resonator. In these conditions the value of the

reference frequency of the transmitter can be in the

same range. In other words the transmitter and the

receiver can operate with different reference fre-

quencies.

Figure 7

max. 13.2V

Figure 8

455 to

510kHz

100pF

PIN 9 : VDD

The supply voltage has to be comprised in the

range 4.75 to 5.25V. When it is applied an internal

power on reset of 0.5s is generated.

The memory position 1 is automatically read if the

mains on option input (Pin 25) is grounded.

PIN 10 : TEST

This pin is used for testing and has to be connected

to VSS.

PIN 11 : I.R. SIGNAL INPUT (see Figure 9)

The integrated receiver decodes signals transmit-

ted by M708, address 9.

The minimum signal to be applied is 0.5V peak-to-

peak. (AC-coupled).

The receiver input section performs the following

tests on the incoming signal to achieve the neces-

sary noise immunity :

- measurement of the pulse distance (time base

synchronization)

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