MITEL MH88510, MH88511 Datasheet
MH88510/11
Subscriber Line Interface Circuit (SLIC)
Preliminary Information
Features
• High Gain v ersio n MH88 511
• Compatible with popul ar MH8 8500
• Operates wi th a wide rang e of bat tery vol tag es
• Constant current battery feed
• Dry line comp atib le
• Overvoltag e and s hort circuit pro tect ion
• Ringing Feed
• Off-hook detection and LED indicator drive
• Dial pulse detection
• Ring trip filter with auto ring trip
• Relay drive r
• Transformerless 2-2 wire conversion
• Low power co nsu mptio n
• Mute of inco ming aud io
• Few externa l com pon ents
Applications
• Line Interface for:
• PABX
• Intercoms
• Key System s
ISSUE 1 April 1995
Ordering Information
MH88510 20 Pin SIL Pa ckag e
MH88511 20 Pin SIL Pa ckag e
0°C to 70°C
Descript io n
The Mitel MH88510/11 Subscriber Line Interface
Circuit provides a complete interface between the
telephone line and a speech switch requiring only
single bidirectional switch per crosspoint. The
functions provided by the MH88510/11 include
bidirectional differential to single ended conversion
in the speech path, line battery feed, ringing feed
and loop and dial pulse detection. The device is
fabricated as a thick film hybrid which incorporates
various technologies for optimum circuit board and
very high reliability.
TF
TIP
RING
RF
VBAT
Tip
Drive
2-2 Wire
Hybrid
Current &
Voltage
Sensing
Ring Short
Protection
AGND
VDD VEE
Figure 1 - Functional Block Diagram
Ring Trip
Line
Super vi si on
SHK
Current/Vo lt age
Filter
RRC
LED
Constant
Control
RRD
Relay
Driver
VRLY
MUTE
JUNC
RGND
2-53
MH88510/11 Preliminary Information
TIP
VDD
RING
RF
TF
VBAT
AGND
VEE
LED
SHK
IC
VDD
AGND
VBAT
MUTE
JUNCTOR
RRD
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Figure 2 - Pin Connections
Pin Description
Pin # Name Description
1TIPTip Lead. Connects to the “Tip” lead (A-wire) of the telephone line .
2VDDPositive Power Supply Voltage. Normally +5V. This provides current for both internal
circuitry as well as the loop. Not internally connected to pin 12.
3 RING Ring Lead. Connects to the “Ring” lead (B-wi re) of the telephon e line.
4RFRing Feed. Connect t o the Ring Relay contact. See Figure 5.
5 TF Leave open circuit
6 VBAT Battery Voltage Supply. Normally -24V or -48V. Not internally connected to pin 14.
7AGNDAnalog Ground. Supply and batte ry ground. Internally conne cted to pin 13. For
optimum perform ance connect pin 7 to pin 13.
8V
EE
9LED
10 SHK
Negative Pow er Su pp ly Voltage. Normally -5V.
LED Drive (Output). Drives an LED directly. A logic low indicates an off-hook condition.
Switch Hook Detect (Output). A logic low indicate s an off-hook condition.
11 IC Internal Connection . This pin is connected internally
12 V
DD
Positive Power Supply Voltage. Normally +5V. This provides current for both internal
circuitry as well as the loop.
13 AGND Analog Gro und. Supply and battery ground. Internally connected to pin 13. For
optimum perform ance connect pin 13 to pin 7.
14 V
BAT
15 MUT E
Battery Voltage Supply. Normally -24V or -48V. Not internally connected to pin 6.
MUTE (Input). A logic low will mute signals coming from Tip-Ring to the JUNC.
16 JUNC Recei ve/ trans mit aud io speech path. (Referen ced to 0V GND).
17 RRD
Ring Relay Drive (Outpu t). Connects to the ring relay coil. A logic low activates the
relay.
18 RGND Relay Gro und . Return path for relay supply votlage. Normally connected to AGND.
19 RRC Ring Relay Control (Input). A logic high activates the Ring Relay Drive (RRD
) outputs.
20 VRLY Relay Positi ve Supply Voltage. Normally +5V. Connects to the relay coil and the relay
supply voltage. An internal clamp diode from VR LY to RGND is provided.
2-54
Preliminary Information MH88510/11
Functional Description
The BORSH Functions
The MH88510/11 performs all of the Borsh functions
of Battery Feed, Overvoltage Protection, Ringing,
Supervision and Hybrid (2-2 Wire).
Battery Feed
The MH88510/11 powers the telephone set with
constant DC loop current for shortlines and
automatically reverts to constant voltage for long
lines. Since the Tip drive is powered down from the
supply, loop current flows through both the V
V
DD
BAT
supply and the VDD supply.
Overvoltage Protection
The MH88510/11 is protected from short ter m (20ms)
transients (+250V) between Tip and Ring, Tip and
ground, and Ring and Ground. However additional
protection circuitry may be needed depending on the
requirements which must be met. Normally, simple
external shunt protection as shown in Figures 5 and
6 is all that is required.
switches ringing voltage on to the line via the
external ring relay. The SLIC provides two internal
300W battery feed resistors through which the
ringing current will flow. A clamp diode is included
which suppresses voltage transients during relay
switching caused by the relay coil. In addition, the
circuit prevents connection of the ringing source
during off-hook conditions. See figure 5 for typical
application.
Hybrid
The 2-2 Wire hybrid circuit converts the incoming
balanced signal at Tip and Ring of the telephone line
into a ground referenced output signal at JUNC of
the SLIC, and converts the ground referenced input
signal at JUNC of the SLIC into a non-balanced
output signal at Tip and Ring of the telephone line.
Line Impedance
The MH88510/11’s Tip-Ring(Zin) impedance is fixed
at 600Ω. For correct SLIC impedance, JUNC must
be appropriately terminated. See AC Electrical
Characteristics.
Supervision
Ringing
The ringing insertion circuitry has the capability to
provide ringing voltage to the telephone set by
simply adding an external relay, ring generator and a
200Ω limiting resistor. The internal relay driver
MH88510/11
SLIC 1
TIP
RING
TIP
RING
1
TIP
3
RING
1
TIP
3
RING
JUNC
MH88510/11
SLIC 2
JUNC
The loop detection circuit determines whether a low
enough impedance is across Tip and Ring to be
recognised as an Off-Hook condition. When an offhook condition occurs, the SHK
and LED outputs
toggle to a logic low level. These outputs also toggle
during incoming dial pulses.
75Ω
16
CROSSPOINT
SWITCH
75Ω
16
CROSSPOINT
SWITC H
Figure 3 - SLIC Crosspoi nt S witc h Connecti on
2-55
Loading...