MH88422
Data Sheet
This country passes equipment approved to CTR21. The MH88422 will not meet this specification. See the
MH88437 data sheet for a CTR21 Product.
Dummy Ringer
This device supports a dummy ringer option which can be configured by the inclusion of external components.
Further details relating to component values and configuration can be obtained from MSAN-154. For example,
Figure 3 shows capacitor C2 which if set to 1.8µF would meet the New Zealand dummy ringer requirements.
MH88422
R2
TIP
26
24
Protection
Circuit
C2
TIP
RLS
VR
20
TF
RVLC
TXIN
5
LC
VDD
1
C1
AGND
3
7
Ring Voltage & Loop
Current Detect Output
11
VX
R3
R1
C3
Audio
Output
Audio
Input
13
C4
18
RING
Notes:
1) R1, R2: Transmit Gain Resistors
2) R3: Receive Gain Resistor
3) C1: 10µF 6V Tantalum
4) C2: Dummy Ringer Capacitor 250V
5) C3, C4: 10µF AC coupling Capacitors
16
RING
Loop Control Input
+
+5V
Figure 3 - Typical Application Circuit
2-4 Wire Conversion
The device converts the balanced 2-Wire input, presented by the line at Tip and Ring, to a ground referenced signal
at VX, as required by modem/fax chip sets.
Conversely the device converts the ground referenced signal input at VR, to a balanced 2-Wire signal across Tip
and Ring.
During full duplex transmission, the signal at Tip and Ring consists of both the signal from the device to the line and
the signal from the line to the device. The signal input at VR, being sent to the line, must not appear at the output
VX. In order to prevent this, the device has an internal cancellation circuit. The measure of attenuation is
Transhybrid Loss (THL).
The Transmit (VX) and Receive (VR) signals are ground referenced (AGND), and biased to 2.5V. The device must
be in the off-hook condition for transmission or reception to take place.
Transmit Gain
The Transmit Gain of the MH88422 is the gain from the differential signal across Tip and Ring to the ground
referenced signal at VX. The internal Transmit Gain of the device is fixed and depends on the variant as shown in
the AC Electrical Characteristics table. For the correct gain, the Input Impedance of the MH88422 variant used,
must match the specified line impedance.
4
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
