MH88437-P
gain, the Input Impedance of the MH88437 must
match the specified line impedance.
With an internal series input resistance of 47kΩ at
the VR+ and VR- pins, external series resistors can
be used to reduce the overall gain.
Overall Receive
(47kΩ+R5)).
Gain
=
0dB+20log
(47kΩ/
Advance Information
For differential applications R6 must be equal to R5
in Figure 5.
Example: If R5 = R6 = 47k in Figure 3, the overall
gain would reduce by 6.0dB.
Supervisory Features
The device is capable of monitoring the line
conditions across Tip and Ring, this is shown in
Figure 5. The Loop Condition Detect pin (LCD),
indicates the status of the line. The LCD output is at
logic 1 when loop current flows, indicating that the
MH88437 is in an off hook state. LCD will also go
high if a parallel phone goes off-hook. Therefore, line
conditions can be determined with the LC and the
LCD pins.
The LOOP pin output voltage VLOOP is proportional
to the line voltage across Tip and Ring scaled down
by a factor of 50 and offset by 2.0V(t-r). With the aid
of a simple external detector the LC, LCD and LOOP
pins can be used to generate the signals necessary
for parallel phone operation, e.g. with a Set Top Box.
See MSAN-154 for further details.
When the device is generating dial pulses, the LCD
pin outputs TTL pulses at the same rate. The LCD
output will also pulse if a parallel phone is used to
dial and when ringing voltage is present at Tip and
Ring.
Mechanical Data
See Figures 12, 13 and 14 for details of the
mechanical specification.
6
MITEL [ MITEL NETWORKS CORPORATION ]
