MH88422
Data Sheet
By adding an external potential divider to VX, it is possible to reduce the overall gain in the application. The output
impedance of VX is approximately 10Ω and the minimum resistance from VX to ground should be 2kΩ.
Example: If R1 = R2 = 2kΩ, in Figure 3, the gain would reduce by 6.0dB.
Receive Gain
The Receive Gain of the MH88422 is the gain from the ground referenced signal at VR to the differential signal
across Tip and Ring. The internal Receive Gain of the device is fixed 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.
The input impedance to ground of VR is 47kΩ and this can be used with an external series resistor to form a
potential divider and reduce the overall gain in the application.
Example: If R3 = 100kΩ, in Figure 3, the Gain would reduce by 3.0dB.
Supervisory Features
The device is capable of monitoring the line conditions across Tip and Ring, this is shown in Figure 3. The Ringing
Voltage Loop Current detect pin (RVLC), indicates the status of the device. The RVLC output is at logic 0 when loop
current flows, indicating that the MH88422 is in an off hook state.
When the device is generating dial pulses, the RVLC pin outputs a TTL pulse at the same rate.
An AC ringing voltage across Tip and Ring will cause RVLC to output a TTL pulse at double the ringing frequency
with an envelope determined by the ringing cadence.
Mechanical Data
See Figure 10, for details of the mechanical specification.
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