ML3371EP datasheet(12/19 Pages) LANSDALE

12 / 19 page

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Page 12 of 19

Issue A

LANSDALE Semiconductor, Inc.

ML3371, ML3372

Figure 11a. Typical Application for ML3371 at 10.7 MHz

–

0.022

VR1 (Squelch Control)

10 k

VR2

10 k

AF Out

to Audio

Power Amp

3.3 k

C10

10.245

MHz

TKANS9443HM

6.8

µH ±6%

1N5817 R5

4.7 k

560

4.7 k

510 k

53 k

51 k

8.2

µH

1st IF 10.7 MHz

from Input

Front End

T2: Toko

2A6597 HK (10 mm)

7MC–8128Z (7 mm)

VCC = 4.0 Vdc

RSSI Output

10 k

0.22

R11

560

51 k

0.01

C17

0.1

0.001

C11

220

C13

0.1

R10

39 k

C14

0.1

Oscillator

muRata

CFU455D2

equivalent

Demodulator

Filter

Mixer

Squelch Trigger

with Hysteresis

Limiter

Amp

1.8 k

C12

0.1

4.7

µF

C15

100 k

1.0 k

Amp

An external positive bias to Pin 12 sets up the squelch trig-

ger circuit such that the audio mute (Pin 14) is open or con-

nected to ground. If Pin 12 is pulled down to 0.9 V or below

by the noise or tone detector, Pin 14 is internally shorted to

ground. There is about 57 mV of hyteresis at Pin 12 to prevent

jitter. Audio muting is accomplished by connecting Pin 14 to

the appropriate point in the audio path between Pin 9 and an

audio amplifier. The voltage at Pin 14 should not be lower than

–0.7 V; this can be assured by connecting Pin 14 to the point

that has no DC component.

Another possible application of the squelch switch may be as

a carrier level triggered squelch circuit, similar to the

MC3362/MC3363 FM receivers. In this case the meter output

can be used directly to trigger the squelch switch when the RF

input at the input frequency falls below the desired level. The

level at which this occurs is determined by the resistor placed

between the meter drive output (Pin 13) and ground (Pin 15).

Figure 11b shows a typical application using the

ML145170/ML145170 PLL device to obtain multiple channel

operation.

Legacy Applications Information

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