V22 and Bell 212A Modem
CMX644A
1.3
Signal List
(Continued)
CMX644A
D2/D5/P4
Pin No.
12
13
Signal
Name
VSS
VBIAS
Type
P
OWER
O/P
The negative supply rail (ground).
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.
An open-drain output for controlling a relay.
The non-inverting input of the receive op-amp.
The inverting input of the receive op-amp.
The output of the receive op-amp.
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.
Input to the Ring or Line Polarity Reversal
Detector.
No connections should be made to these pins.
Description
14
15
16
17
18
RLYDRV
RXP
RXN
RXO
RT
O/P
I/P
I/P
O/P
BI
19
RD
I/P
20, 21,
22
23
-
N/C
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.
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.
24
VDD
P
OWER
Notes:
I/P
O/P
N/C
B/I
T/S
=
=
=
=
=
Input
Output
No (external) Connections
Bidirectional
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
CMLMICRO [ CML MICROCIRCUITS ]
