PIN DESCRIPTION

5V

Fmod

D5

D6

Figure 2

5V

Fmod

D5

D6

5V

Fmod

Figure 1

D1 - D2

These pins input the AC signal modulated at Fmod

coming from ST75951 through the capacitive iso-

lation barrier.

D3 - D4

These pins output the AC signal modulated at Fmod

in off-hook mode and at Fmod/2 in CLID mode to

ST75951 through the capacitive isolation barrier.

In ring mode, these pins output the ring information,

D5 - D6

ing from ST75951 through the capacitive isolation

barrier.

These signals control the off-hook and CLID exter-

nal transistor switches and are sent to the internal

transmit demodulator and receive modulator.

sent on D5 and D6 inputs with an opposite phase

(see Figure 1). With a dedicated application it is

sent on D5 input only (see Figure 2). With a dedi-

cated application it is possible to reduce the input

LINE

DC positive line connection and line AC signal output.

LCOM

Negative line connection.

LINI

Line AC signal input in off-hook mode.

AIN - AOUT

The transmit signal coming from AIN pin is injected

in AOUT pin to the 2W/4W internal converter stage.

The line echo is minimized if R3, connected be-

tween LINE and VDR pins is equal to 620

Ω.

GAIN

R1 connected on this pin fixes the transmit gain.

The R1 recommanded value, on a 600

Ω AC line

termination, is 82

Ω.

RIN

During the ring burst, a 1MHz oscillator is powered

and D4 to indicate the ring presence.

IREF

Internal reference current source setting, R4 must

be equal to 82k

Ω.

VDR

Power supply for the transmit and receive paths in

Off-Hook mode.

VDREF

Internal resistor reference.

SET

Line gyrator AC/DC filter.

OHC

opposite phase, this pin puts ON the hook switch

external Q1/Q2 transistor stage.

IDC

ON the CLID external Q3/Q4 transistor stage.

R2 limits the line current in CLID mode at 1mA

max.

COM

Commun output for off-hook and CLID external

transistor stages

TER1 - TER2

These pins control the external Q5 transistor, in

which the main part of the line current goes

requirements.

IDI

Line AC signal input in CLID mode.

IDG

Power supply for the receive path in CLID mode.

LIM1 - LIM2

200mA over current detection for device protection.

TOFF

Internal Reference Supply.

ST952

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