MH88437AS-PI datasheet(6/16 Pages) MITEL

6 / 16 page

MH88437-P

Advance Information

gain, the Input Impedance of the MH88437 must

match the speciﬁed line impedance.

With an internal series input resistance of 47k

Ω at

the VR+ and VR- pins, external series resistors can

be used to reduce the overall gain.

Overall

Receive

Gain

0dB+20log

(47k

Ω/

(47k

Ω+R5)).

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.

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