2-12

MH88400

Preliminary Information

Figure 2 - Pin Connections

Pin Description

Pin #

Name

Description

1VDD

Positive Power Supply Voltage. +5V.

2AGND

Analog Ground. 4-Wire Ground. Normally connected to System Ground,

3LC

Loop Control (Input). A logic low activates internal circuitry which provides a dc

termination across Tip and Ring. Used for seizing the line and dial pulsing

4

RVLC

Ring Voltage and Current Detect (Output). A logic low indicates that loop current is

detected. The loop current can be due to the external monitor phone or the MH88400 in

the off- hook mode. The RVLC outputs pulses when the external monitor phone is dial

pulsing or when the MH88400 is dial pulses via the LC input. In addition, when the

MH88400 is in the on-hook mode, a pulsing output indicates that ringing voltage is

across the Tip and Ring leads; the pulsing outputs frequency is twice the ringing

frequency.

5SHK

Switch Hook Detect (Output). This is an optional output which can be used with the

PHS input and an external phone. When loop current flows from PHS to TIP, SHK goes

to logic low.

6VX

Transmit (Output). 4-Wire ground(AGND) referenced audio output, biased at 2.5V.

Outputs for both off-hook and on-hook.

7VR

Receive (Input). 4-Wire ground (AGND) referenced audio input, biased at 2.5V. LC

must be activated low and loop current must be flowing.

8NC

No Connection. This pin is not connected internally

9

RING

Ring Lead. Connects to the “Ring” lead of the central office through a relay contact. The

central office “Tip” and “Ring” leads may be interchanged

10

TXIN

Transmit (Input). Connects to the “Ring” lead of the central office through a coupling

capacitor.

11

TF

Tip Feed. Connects to the “Tip” lead of the central office through an internal resistor and

an optional external resistor.

12

PHS

Monitor Phone Sense (Input). This is an optional input which can be used with the

SHK output and an external phone. When loop current flows from PHS to TIP, SHK goes

to logic low.

13

RLS

Ring Loop Sense (Input). Sense node for ringing voltage detector and the loop current

detector.

14

TIP

Tip Lead. Connects to the “Tip” lead of the central office through an optional relay

contact. The central office “Tip” and “Ring” leads may be interchanged.

RLS

PHS

TF

TXIN

LC

NC

TIP

AGND

RING

RVLC

SHK

VX

VR

VDD

1

2

3

4

5

6

78

9

10

11

12

13

14