CMX644A Просмотр технического описания (PDF) - CML Microsystems Plc

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CMX644A

V.22 and Bell 212A Modem

CML Microsystems Plc 

V22 and Bell 212A Modem

CMX644A

1.3 Signal List (Continued)

CMX644A

D2/D5/P4

Pin No.

Signal

Name

Type

Description

12

VSS

POWER The negative supply rail (ground).

13

VBIAS

O/P A bias line for the internally circuitry, held at ½

VDD. This pin must be decoupled by a

capacitor mounted close to the device pins.

14

RLYDRV

O/P An open-drain output for controlling a relay.

15

RXP

I/P The non-inverting input of the receive op-amp.

16

RXN

I/P The inverting input of the receive op-amp.

17

RXO

O/P The output of the receive op-amp.

18

RT

BI

Open-drain output and Schmitt trigger input

forming part of the Ring or Line Polarity

Reversal detector. An external resistor to VDD

and a capacitor to VSS should be connected to

RT to filter and extend the RD input signal.

19

RD

I/P Input to the Ring or Line Polarity Reversal

Detector.

20, 21,

22

-

N/C No connections should be made to these pins.

23

ATODCAP

O/P The reference voltage for the internal A to D of

the receiver. This pin must be decoupled by a

capacitor mounted close to the device pins.

24

VDD

POWER The positive supply rail. Levels and thresholds

within the device are proportional to this

voltage. Should be decoupled to VSS by a

capacitor mounted close to the device pins.

Notes: I/P = Input

O/P = Output

N/C = No (external) Connections

B/I = Bidirectional

T/S = Tristate

This device is capable of detecting and decoding small amplitude signals. It is recommended that the printed

circuit board is laid out with a ground plane in the CMX644A area to provide a low impedance connection

between the VSS pin and the VDD and VBIAS decoupling capacitors. The receive path should be protected

as much as possible from extraneous signals.

© 2000 Consumer Microcircuits Limited

5

D/644A/6

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