2-53
Features
High Gain version MH88511
Compatible with popular MH88500
Operates with a wide range of battery voltages
Constant current battery feed
Dry line compatible
Overvoltage and short circuit protection
Ringing Feed
Off-hook detection and LED indicator drive
Dial pulse detection
Ring trip filter with auto ring trip
Relay driver
Transformerless 2-2 wire conversion
Low power consumption
Mute of incoming audio
Few external components
Applications
Line Interface for:
PABX
Intercoms
Key Systems
Description
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 AGND VDD VEE
SHK
LED
RRC
RRD VRLY RGND
MUTE
JUNC
Tip
Drive
Current &
Voltage
Sensing
Ring Short
Protection
2-2 Wire
Hybrid
Constant
Current/Voltage
Control
Ring Trip
Filter
Line
Supervision
Relay
Driver
ISSUE 1
April 1995
Ordering Information
MH88510
20 Pin SIL Package
MH88511
20 Pin SIL Package
0
C to 70
C
Figure 1 - Functional Block Diagram
MH88510/11
Subscriber Line Interface Circuit (SLIC)
Preliminary Information
2-54
MH88510/11
Preliminary Information
Figure 2 - Pin Connections
Pin Description
Pin #
Name
Description
1
TIP
Tip Lead. Connects to the "Tip" lead (A-wire) of the telephone line.
2
VDD
Positive 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-wire) of the telephone line.
4
RF
Ring Feed. Connect to 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.
7
AGND
Analog Ground. Supply and battery ground. Internally connected to pin 13. For
optimum performance connect pin 7 to pin 13.
8
V
EE
Negative Power Supply Voltage. Normally -5V.
9
LED
LED Drive (Output). Drives an LED directly. A logic low indicates an off-hook condition.
10
SHK
Switch Hook Detect (Output). A logic low indicates 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 Ground. Supply and battery ground. Internally connected to pin 13. For
optimum performance connect pin 13 to pin 7.
14
V
BAT
Battery Voltage Supply. Normally -24V or -48V. Not internally connected to pin 6.
15
MUTE
MUTE (Input). A logic low will mute signals coming from Tip-Ring to the JUNC.
16
JUNC
Receive/transmit audio speech path. (Referenced to 0V GND).
17
RRD
Ring Relay Drive (Output). Connects to the ring relay coil. A logic low activates the
relay.
18
RGND
Relay Ground. 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 Positive Supply Voltage. Normally +5V. Connects to the relay coil and the relay
supply voltage. An internal clamp diode from VRLY to RGND is provided.
TIP
VDD
RING
TF
VBAT
AGND
VEE
LED
SHK
IC
VDD
AGND
VBAT
MUTE
JUNCTOR
RRD
RF
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
2-55
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
V
DD
supply, loop current flows through both the V
BAT
supply and the V
DD
supply.
Overvoltage Protection
The MH88510/11 is protected from short term (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.
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
200
limiting resistor. The internal relay driver
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 600
. For correct SLIC impedance, JUNC must
be appropriately terminated. See AC Electrical
Characteristics.
Supervision
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 off-
hook condition occurs, the SHK and LED outputs
toggle to a logic low level. These outputs also toggle
during incoming dial pulses.
Figure 3 - SLIC Crosspoint Switch Connection
MH88510/11
MH88510/11
TIP
RING
TIP
RING
TIP
RING
TIP
RING
JUNC
JUNC
75
75
CROSSPOINT
SWITCH
CROSSPOINT
SWITCH
16
16
1
3
1
3
SLIC 1
SLIC 2
MH88510/11
Preliminary Information
2-56
The SHK output has low drive capability while the
LED output can drive an LED directly. The detection
circuit engages a ringing filter during applied ringing.
The ringing filter ensures that the SHK output toggles
at the ringing cadence and not at the ringing
frequency. The ring trip detection circuit also
prevents false off-hook detection due to the current
associated with the AC ringing voltage as well as
current transients when the ringing votlage is
switched in and out.
Hybrid
The 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.
Return Loss at Tip-Ring
To maximise return loss, the impedance at Tip-Ring
should match the SLIC's impedance (600
).
However, the SLIC's input impedance is dependent
on the JUNC termination resistance. For a 600
SLIC input impedance, the JUNC must be
terminated with 754
.
Figure 2 illustrates a typical connection between two
SLICs through two crosspoint switches. Optimum
return loss occurs when JUNC is terminated with
754
. Since the JUNC input/output is 604
and the
crosspoint switches resistance are 75
+ 75
, this
configuration gives optimum return loss as shown in
Figure 3.
MUTE
A logic low at the MUTE input results on, muted
signals coming from Tip and Ring to the JUNC
terminal while allowing signals from the JUNC
terminal to Tip and Ring to be transmitted.
Tip-Ring Drive Circuit
The audio input ground referenced signal at JUNC is
converted to a differential output signal at Tip and
Ring. The output signal consists of the audio signal
superimposed on the DC battery feed current. The
Tip-Ring drive circuit is optimsed for good 2-Wire
longitudinal balance.
In addition, the Tip-Ring Drive Circuit has the
capability to drive a dry line (a line with no DC
current flowing); the AC Electrical Characteristics
apply (except for longitudinal balance), even when
the loop current drops to zero. Therefore, the
MH88510 has the capability to drive a line much
longer than 2000
providing the user is not
concerned with loop current, SHK detection or
ringing generator current.
Short Circuit Protection
The MH88510 is protected from long term (infinite)
short circuit conditions occurring between Tip and
Ring, Tip and AGND, and Ring and AGND.
Line Impedance
The MH88510's Tip-Ring (Zin) impedance is fixed at
600
. For correct SLIC impedance, JUNC must be
appropriately terminated. See AC Electrical
Characteristics.
Transmit and Receive Gain
Transmit Gain (JUNC to Tip-Ring) and Receive Gain
(Tip-Ring to JUNC) are fixed. For correct gain, the
SLIC input impedance must match the line
impedance and JUNC must be appropriately
terminated.
2-57
Preliminary Information
MH88510/11
Figure 4 - Return Loss VS Junctor Load Impedance
Figure 5 - Typical Application Circuit
10
20
30
40
50
60
550
600
650
700
750
800
850
900
950
TYPICAL
RETURN
LOSS
LOAD IMPEDANCE ON JUNCTOR (
)
(dB)
TIP
RING
RINGING
GENERATOR
90VRMS
OPTIONAL
PROTECTION
CIRCUIT
K1
R1
-48V
-5V
C1
C2
+5V
K1
DS1
AUDIO
INPUT/OUTPUT
MUTE CONTROL
INPUT
SWITCH HOOK
OUTPUT
OFF-HOOK LED
RING CONTROL
INPUT
TIP
RING
RF1
VBAT
VEE AGND VDD RGND
VRLY
RRD
LED
SHK
MUTE
JUNC
RRC
1
3
4
6,14
8
13
12
18
20
17
19
9
10
15
16
MH88510/11
Notes:
R1= 200
, 1/4W, 5%
K1= Relay E/M 5V, 1 form C
C1, C2 = 0.1uF, 50V, Ceramic
~
2-58
MH88510/11
Preliminary Information
Absolute Maximum Ratings
Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied.
Typical figures are at 25
C with nominal+ 5V supplies and are for design aid only: not guaranteed and not subject to production testing.
DC Electrical Characteristics are over recommended operating conditions with V
DD
at +5.0V and V
EE
at -5V 5% unless otherwise stated.
Typical figures are at 25
C with nominal+ 5V supplies and are for design aid only: not guaranteed and not subject to production testing.
x
Supply Current and Power Consumption characteristics are over recommended operating conditions with V
DD
at 5.0V, V
EE
at -5.0V and V
BAT
at -48V.
Note that
loop current flows through both the V
BAT
and the V
DD
supply.
y
SHK output consists of a 100k
resistor in series with an op-amp with a minimum output voltage swing of 3.25V.
z
LED outputs consists of a 2.5k
resistor in series with SHK op-amp output.
RRC input consists of a 5kW resistor in series with the base lead of the relay driver transistor (grounded emitter).
{
The MUTE input is internally pulled up. With no input connection, the voltage level at the MUTE input is typically at 1.5V.
Parameter
Symbol
Min
Max
Units
1
DC Supply Voltage
V
DD
V
EE
-0.3
0.3
15
-15
V
V
2
DC Battery Voltage
V
BAT
0.3
-60
V
3
DC Relay Voltage
V
RLY
-0.3
20
V
4
AC Ring Generator Voltage
150
V
RMS
5
Storage Temperature
T
S
-55
125
C
Characteristics
Sym
Min
Typ
Max
Units
Test Conditions
1
DC Supply Voltage
V
DD
V
EE
4.75
-4.75
5.0
-5.0
7.35
-8.40
V
V
2
DC Battery Voltage
V
BAT
-23
-48
-56
V
3
DC Relay Voltage
V
RLY
5.0
15
V
4
AC Ring Generator Voltage
Ringing Generator Frequency
17
90
105
33
V
RMS
Hz
5
Operating Temperature
T
OP
0
70
C
DC Electrical Characteristics
Characteristics
Sym
Min
Typ
Max
Units
Test Conditions
1
Supply Current: Open Loop
Normal Loop
Short Loop
I
DD
I
EE
I
BAT
I
DD
I
EE
I
BAT
I
DD
I
EE
I
BAT
15
15
15
43
15
43
43
15
43
mA
mA
mA
mA
mA
mA
mA
mA
mA
R
LOOP
= Open
R
LOOP
= 1000
R
LOOP
= 0
2
Power Consumption
x
: Open Loop
Normal Loop
Short Loop
PC
PC
PC
880
2360
2360
mW
mW
mW
R
LOOP
= Open
R
LOOP
= 1000
R
LOOP
= 0
3
Low Level Output Voltage
y
High Level Output Voltage
V
OL
V
OH
-3.0
3.0
V
V
I
OL
= 2
A
I
OH
= 2
A
4
Sink Current, LED to AGND
y
Sink Current, LED to VDD
I
OL
I
OH
0.6
2.5
mA
mA
V
OL
= -1.5V
V
OL
= 3.25V
5
Sink Current, Relay to VDD
Clamp Diode Current
I
OL
I
CD
100
150
mA
mA
V
OL
= 0.35V
6
High Level Input Voltage
z
V
IH
3.5
V
I
IL
= 1.0mA
7
Low Level Input Voltage
{
V
IL
0.8
V
I
IL
= 0.5mA
2-59
Preliminary Information
MH88510/11
AC and DC Loop Electrical Characteristics*
*
AC and DC Loop Electrical Characteristics are over recommended operating conditions unless otherwise stated.
Typical figures are at 25
C with nominal + 5V supplies and are for design aid only.
x
The SLIC can be loaded with an AC impedance as low as 2200
without generating a false SHK output. Since each REN represents 8k
,
the SLIC can drive a REN of 3.6 without generating a false SHK output.
y
See section on Tip-Ring Drive Circuit for driving longer lines.
AC Electrical Characteristics
Typical figures are at 25
C with nominal + 5V supplies and are for design aid only.
Characteristics
Sym
Min
Typ
Max
Units
Test Conditions
1
Maximum AC Ringing
Current Rejection
x
44
mA
2
Ring Trip Detect Time
125
ms
3
Operating Loop Current
V
BAT
= -48V
V
BAT
= -23V
I
IP
18
18
23
23
28
28
mA
mA
R
Loop
< 2000
R
Loop
< 600
4
Maximum Operating Loop
Resistance
y
V
BAT
= -48V
V
BAT
= -23V
R
IP
2000
600
I
Loop
= 18mA
I
Loop
= 18mA
5
Loop Current at
Off-Hook Detect Threshold
I
SH
8
9
10
11
12
13
A
A
V
DD
= 5.0V, V
EE
= -5.0V
V
DD
= 7.0V, V
EE
= -8.0V
Characteristics
Sym
Min
Typ
Max
Units
Test Conditions
1
Return Loss at 2-Wire
20
30
dB
Reference 600
@ 1kHz
2
Impedance at Junctor
604
3
Longitudinal to Metallic Balance
50
60
dB
40Hz - 4kHz
4
Longitudinal to Junctor Balance
50
60
dB
40Hz - 4kHz
5
Signal Output Overload Level
at 2-Wire
at Junctor
3.5
3.5
dBm
dBm
% THD < 5%
Reference: 600
Reference: 754
6
Total Harmonic Distortion
at 2-Wire
at Junctor
THD
1.0
1.0
%
%
Input 0.5V 1kHz
7
Idle Channel Noise
at 2-Wire
at Junctor
Nc
12
12
dBrnc
dBrnc
Reference: 600
Reference: 754
8
Power Supply Rejection Ratio at
2-Wire and Junctor
V
DD
V
EE
V
BAT
PSRR
25
25
25
dB
dB
dB
Ripple 0.1V 1kHz
9
Mute Attenuation
30
dB
Input 0.5V MUTE
= 0.0V @1kHz
2-60
MH88510/11
Preliminary Information
AC Gains Table - MH88510
Typical figures are at 25
C with nominal + 5V supplies and are for design aid only.
AC Gains Table - MH88511
AC Electrical Characteristics are over recommended operating conditions unless otherwise stated.
Typical figures are at 25
C with nominal + 5V supplies and are for design aid only.
Note1: All of the above test conditions use 754
connected between JUNC and GRD, and 600W connected between Tip and Ring unless
otherwise stated.
Note 2: All of the above test conditions use 200Hz to 6400Hz unless otherwise stated.
Figure 6 - Typical Protection Circuit
Characteristics
Sym
Min
Typ
Max
Units
Test Conditions
1
Gain 2-Wire to Junctor
1.05
0.42
1.12
0.98
1.19
1.51
V/V
dBV
Input 0.5V 1kHz
Input 0.5V 1kHz
2
Frequency Response Gain
(relative to gain at 1kHz)
-0.3
0.3
dB
200Hz - 3400Hz
3
Gain Junctor to 2-Wire
0.96
-0.35
1.00
0.0
1.04
0.35
V/V
dBV
Input 0.5V 1kHz
Input 0.5V 1kHz
4
Frequency Response Gain
(relative to gain at 1kHz)
-0.3
0.3
dB
200
z - 3400Hz
Characteristics
Sym
Min
Typ
Max
Units
Test Conditions
1
Gain 2-Wire to Junctor
1.15
0.21
1.19
1.50
1.22
1.72
V/V
dBV
Input 0.5V 1kHz
Input 0.5V 1kHz
2
Frequency Response Gain
(relative to gain at 1kHz)
-0.3
0.3
dB
200Hz - 3400Hz
3
Gain Junctor to 2-Wire
1.04
0.34
1.08
0.67
1.11
0.91
V/V
dBV
Input 0.5V 1kHz
Input 0.5V 1kHz
4
Frequency Response Gain
(relative to gain at 1kHz)
-0.3
0.3
dB
200Hz - 3400Hz
TIP
RING
MH88510/11
AGND
PROTECTION CIRCUIT
TIP
RING
RV3
RV2
RV1
EARTH GROUND
SYSTEM
GROUND
1
3
7
Notes
RV1,2,3 = 175VAC, 225VAC, 15J
GE V175LA2 or similar
2-61
Preliminary Information
MH88510/11
Figure 7 - MH88511 as a Trunk Interface Application
Figure 8a - Line to Line
MH88511
J
T
R
T1
C2
R1
R2
Q1
R3
C4
D3
D6
D4
D5
Q2
C3
Q3
R7
+5V
D8
C5
R4
C6
R6
R5
D7
+5V
R9
VAR1
TIL111
RING
DET
VAR2
R8
VAR3
2
6
4
5
1
TIP
RELAY
LINE SEIZE
RING
D9
COMPONENTS
D1,D2,=IN4732
D3,D4,D5,D6,D7=IN4003
D8=IN4148
D9=IN5246B
VAR1,VAR2,VAR3-V130LA20A
C1,C3=10
F,60V,5%
C2=1.0
F,100V,5%
C4=0.1
F,100V,5%
C5=0.01
F,100V,5%
C6=0.33
F,200V,5%
R1=1/4W,1%,6.8k
R2,R5=1/4W,10%,10k
R3=1/2W,10%,50
R4=1/4W,10%,680
R6=1/4W,10%,100k
R7=1/4W,10%,1k
R8,R9=1/2W,10%,10
Q1=MPSA90
Q2=ZN6716
Q3=BC238
T1=FILTRAN TPF712 (or EQUIVALENT) 600
:1
1
3 C1
D2
D1
MH88510
MT8816
MH88510
1dB
-2dB
0dB
0dB
1dB
-1dB
-1dB
2-62
MH88510/11
Preliminary Information
Figure 8b- Line to Line
Figure 9 - Mechanical Data
MH88511
MT8816
MH88510
1dB
-2dB
0dB
1.2dB
-0.7dB
-0.7dB
-0.2dB
0dB
-0.2dB
C.O.
T1
2.00 + 0.020
(50.8 + 0.5)
0.58+0.02
(14.7+0.5)
0.12 Max
(3.1 Max)
0.010 + 0.002
(0.25 + 0.05)
0.080 Max
(2.0 Max)
Side View
0.05 + 0.01
(1.3 + 0.5)
*
*
*
0.05 + 0.02
(1.3 + 0.05)
0.020 + 0.05
(0.51 + 0.13)
0.100 + 0.10
(2.54 + 0.13)
0.18 + 0.02
(4.6 + 0.5)
1 2 3 4
19 20
Notes:
1) Not to scale
2) Dimensions in inches).
3) (Dimensions in millimetres).
*Dimensions to centre of pin &
tolerance non accumulative.
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