LA76818 Просмотр технического описания (PDF) - SANYO -> Panasonic

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LA76818

The BUS Control Functions of LA76818 (Tentative)

SANYO -> Panasonic 

Technical Note of LA76818

2002/01/23

PIN 4 (RF AGC OUTPUT)

This is a RF AGC output pin. The reference voltage, which is controlled by RF AGC

D/A, and the IF AGC voltage is input into differential amplifier, then the output can be

achieved at the open collector. The time constant is determined by the value of the

external R & C. The maximum drive current of Q1 is 1mA. The maximum DC voltage

of pin 4 is 9V. Please change the value of R, which is depending on the specification of

tuner, to decide the DC voltage output.

４

100

RF

AGC

D/A

2nd

IF.AGC

Filter

Output

To BUS

Status

A) The circumference circuit of pin 4

A comparator, which is used for BUS statue, is built-in this IC. The reference voltage

of this comparator is set as Vcc*(6/7) and compare with voltage below:

Vcc – {Io*(1/5)*70kΩ}

* Io is the output current of pin 4.

RF.A

IF.VC

４

８

100

Io

1 Io

70k

5

Q1

Q2

Ra

＋

To

−

BUS

Rb

Ra:Rb=1:6

Io: max 1mA

B)The circumference circuit of pin 4

18/ 46

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