2-73
Features
Full duplex operation
Two complete circuits per package
Transformerless 2-4 Wire (4-2 Wire) conversion
+ 5V operation
Wide bandwidth (50kHz)
Small Package Size
Applications
4-2 Wire and 2-4 Wire conversion for:
MH88630/631, MH88632, MH88500 & MT8840
PBX
Key Telephone System
Channel bank
Voice Mail
Terminal Equipment
Digital Loop Carrier
Modem
Intercom
Description
The Mitel MH88524 (Dual 2-4 wire Circuit) provides
two independent interfaces between4-Wire devices
such as the MH88631 COIC (Central Office Interface
CIrcuit) and a speech switch such as the MT8814
(Analog Switch Array), requiring only a single
bidirectional switch per crosspoint. The MH88524
can accommodate two full duplex audio links. The
device is fabricated as a thick film hybrid which
incorporates various technologies for optimum circuit
design and very high reliability.
Receive Gain
Circuit1
Transmit Gain
Circuit 1
Receive Gain
Circuit 2
2-4 Wire
Circuit 1
2-4 Wire
Circuit 2
Transmit Gain
Circuit 2
RX1
TX1
RX2
TX2
JUN1
JUN2
VDD
VEE
AGND
ISSUE 4
April 1995
Ordering Information
MH88524
10 Pin SIL Package
0
C to 70
C
Figure 1 - Functional Block Diagram
MH88524
Dual 2-4 Wire Circuit
Preliminary Information
2-74
MH88524
Preliminary Information
Figure 2 - Pin Connections
Absolute Maximum Ratings
*
* Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied.
Recommended Operating Conditions
* Typical figures are at 25
C with nominal
+
5V supplies and are for design aid only.
Pin Description
Pin #
Name
Description
1
RX1
Receive 1 (Input). 4-Wire ground (AGND) referenced audio output.
2
JUN1
Junctor 1 (Transmit and Receive). Ground referenced transmit and receive speech path.
3
TX1
Transmit 1. 4-Wire ground (AGND) referenced audio output.
4
VDD
Positive Supply Voltage. Typically +5V.
5
AGND
Analog Ground. 2-Wire and 4-Wire ground. Normally connected to System Ground.
6
VEE
Negative Supply Voltage. Typically -5V.
7
IC
Internal Connection. This pin is internally connected.
8
TX2
Transmit 2 (Output). 4-Wire ground AGND) referenced audio output.
9
JUN2
Junctor 2 (Transmit and Receive). Ground referenced transmit and receive speech path.
10
RX2
Receive 2 (Input). 4-Wire ground (AGND) referenced audio output.
Parameter
Sym
Min
Max
Units
Comments
1
DC Supply Voltage
V
DD
V
EE
-0.3
+0.3
15
-15
V
V
With respect LGND
2
Storage Temperature
T
S
-55
125
C
Parameter
Sym
Typ*
Min
Max
Units
Comments
1
DC Supply Voltage
V
DD
V
EE
5.0
-5.0
4.75
-4.75
10
-10
V
V
2
Operating Temperature
T
OP
0
70
C
1
2
3
4
5
6
7
8
9
10
RX1
JUN1
TX1
VDD
AGND
VEE
IC
TX2
JUN2
RX2
2-75
Preliminary Information
MH88524
DC Electrical Characteristics
DC 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.
AC Electrical Interdependence Characteristics
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.
Characteristics
Sym
Min
Typ*
Max
Units
Test Conditions
1
Supply Current
I
DD
P
EE
4
4
mA
V
DD
= +5.0
V
EE
= 5.0
2
Power Dissipation
PC
40
mW
V
DD
= +5.0
V
EE
= 5.0
Characteristics
Sym
Min
Typ*
Max
Units
Test Conditions
1
Cross, Circuit 1 or 2
JUN1 to JUN2
JUN1 to TX2
RX1 to JUN2
RX1 to TX2
80
80
80
80
dB
dB
dB
dB
Input 1.0V
200Hz-3400Hz
JUN1 to JUN2
JUN1 to TX2
RX1 to JUN2
RX1 to TX2
60
60
60
60
dB
dB
dB
dB
200Hz-50kHz
2
Crosstalk, Circuit 1 or 2
JUN1 to JUN2
JUN1 to TX2
RX1 to JUN2
RX1 to TX2
80
80
80
80
dB
dB
dB
dB
Input 1.0V
200Hz-3400Hz
JUN1 to JUN2
JUN1 to TX2
RX1 to JUN2
RX1 to TX2
60
60
60
60
dB
dB
dB
dB
200Hz-50kHz
2-76
MH88524
Preliminary Information
AC Electrical Characteristics
* Typical figure are at 25
C with nominal
+
5V supplies and are for design aid only.
AC Electrical Characteristics are over recommended operating conditions unless otherwise stated.
Both of the 2-4 Wire circuits are tested. TX, RX and Junctor actually refer to TX1, RX1 and JUN1; and TX2, RX2 and JUN2.
All of the above test conditions use 754
connected between Junctor and AGND, unless otherwise stated.
All the above test conditions use 200Hz to 3400Hz unless otherwise stated.
Notes:
x
RX is connected to AGND, see Figure 3.
y
See Figure 5.
z
See Figure 4.
Characteristics
Sym
Min
Typ*
Max
Units
Test Conditions
1
Return Loss at junctor
x
(Ref. = 604
)
46
40
dB
dB
200-3400Hz
200-50kHz
2
Impedance at Junctor
604
3
Transhybrid Loss
y
(Junctor - 754
)
42
36
dB
dB
200-3400Hz
200-50kHz
4
Transhybrid Loss
z
(Frequency = 1kHz)
18
21
dB
dB
Junctor = 600
Junctor = 900
5
Transhybrid Loss
(Frequency = 50kHz)
15
18
dB
dB
Junctor = 600
Junctor = 900
6
Input Impedance at RX
10k
7
Output Impedance at TX
5
8
Gain RX to Junctor
ARJ
0.99
-0.1
1.00
0.0
1.01
0.1
V/V
dBV
Input 0.5V 1kHz
9
Frequency Response Gain
(relative to gain at 1kHz)
-0.1
-0.1
0.1
1.0
dB
dB
200-3400Hz
200-50kHz
10
Gain junctor to TX
AJT
0.99
-0.1
1.00
0
1.01
0.1
V/V
dBV
Input 0.5V 1kHz
11
Frequency Response Gain
relative to gain at 1kHz
-0.1
-0.1
0.1
0.1
dB
dB
200-3400Hz
200Hz-50kHz
12
Signal Output Overload Level
at TX
at Junctor
6.0
6.0
dBm
dBm
%THD<5%
Reference: 600
Reference: 754
13
Total Harmonic Distortion
RX to Junctor
Junctor to TX
RX to Junctor
Junctor to TX
THD
0.4
0.4
1.0
1.0
%
%
%
%
Input 0.5V 1kHz
200-3400Hz
200-3400Hz
200-50kHz
200-50kHz
14
Idle Channel Noise
at TX
at Junctor
Nc
2
2
dBrnC
dBrnC
Reference: 600
Reference 754
15
Power Supply Rejection Ratio
at TX and Junctor
V
DD
V
EE
PSRR
40
40
dB
dB
Ripple 0.1V 1kHz
Preliminary Information
MH88524
2-77
Functional Description
The MH88524 is a Dual 2-4 Wire Circuit used to
interface between ground reference 2-Wire circuitry
and ground referenced 4-Wire circuitry. The device
can accommodate two full duplex audio links.
Hybrid
The 2-4 Wire hybrid circuit separates the ground
reference full duplex signal at JUNi (where i=1 or 2)
of the switched line into receive and transmit ground
referenced signals the RXi (Receive) and TXi
(Transmit). The hybrid also prevents the input signal
at RXi from appearing at TXi. The degree to which
the hybrid minimises the contribution to the RXi
signal at the TXi output is specified as transhybrid
loss. For maximising transhybrid loss, see the
Transhybrid Loss section.
The 4-Wire side can be interfaces to a COIC such as
the MH88631 for use in analog voice switched
systems; or a filter/codec, such as the Mitel MT896X,
for use in digital voice switched systems.
The 2-wire side can be interfaces to a crosspoint
switch such as the MT8816 or a junctor SLIC such
as the MH88510 for use in analog voice switched
systems.
Return Loss at Junctor
The MH88524's Junctor impedance (Zin) is fixed at
604
nominal when RXi and TXi in a feedback loop
as shown in Figure 6, the JUNi impedance will
change, see Return Loss with Interface Circuit.
Return Loss with Interface Circuit
To maximise return loss at Tip-Ring of the Interface
Circuit, the termination impedance at Tip-Ring of the
Interface Circuit (COIC or SLIC) should match the
Interface Circuit's input impedance (600
, 900
or
complex). However, with the inclusion of the
MH88524, the interface circuit's input impedance is
dependent on the JUNi termination resistance. For
optimum return loss the JUNi should be terminated
with 754
.
Figure 6, shows, illustrates a typical connection
between an Interface Circuit (MH88631) and the
MH88524. Note how the return loss occurs when
JUNi is terminated with 754
.
Figure 8 illustrates a typical connection between two
interface circuits (MH88631), through an MH88524
and two crosspoint switches. Optimum return loss
occurs when JUNi is terminated with 754
. Since the
JUNi input/output impedance is 604
, the MH88510
JUNC input/output impedance is 604
, and the
crosspoint switches resistance are 75W + 75
, this
configuration gives optimum return loss.
Transhybrid Loss
THL = log (VRX/VTX)
Transhybrid loss is maximised when the JUNi
termination impedance is 754W. In addition, good
transhybrid loss is indicated in Figure 4 and AC
Electrical Characteristics.
Fixed Transmit and Receive Gain
Transmit Gain (JUNi to TXi, TXi/JUNi) and receive
Gain (RXi to JUNi, JUNi/RXi) are both fixed at 0dBV
providing the MH88524 JUNi impedance is 754
.
Application with MT8840, MH88500 and
MH88524
Figure 11 illustrates an application for the
MH88524's wide bandwidth. The MT8840 requires a
2-4 Wire converter which has good transhybrid loss
at 32kHz. Since the MH88524 operates to 50kHz, it
is ideal for this application. In addition, if a SLIC
(Subscriber Line Interface Circuit) is required, the
MH88500 can also be used since it also has a 604
Junctor and a wide bandwidth.
Mechanical Data See Figure 12.
2-78
MH88524
Preliminary Information
Figure 3 - Return Loss at Junctor vs Frequency with MH88524
Figure 4 - Transhybrid Loss vs Junctor Resistance with MH88524
Figure 5 - Transhybrid Loss vs Frequency with MH88524
100
10,000
50
40
30
20
10
0
Frequency (Hz)
1000
100,000
TYPICAL
RETURN
LOSS
(dB)
RETURN
LOSS
JUN1
AGND
TX1
TX1
MH88524
Ref: 604
550
60
50
40
30
20
10
Frequency (Hz)
800
TYPICAL
TRANSHYBRID
LOSS (dB)
JUNCTOR
RESISTANCE
JUN1
AGND
TX1
TX1
MH88524
600
650
700
750
850
900
950
TRANSHYBRID LOSS
Frequency (Hz)
TYPICAL
TRANSHYBRID
LOSS (dB)
JUNCTOR
RESISTANCE
JUN1
AGND
TX1
TX1
MH88524
100
10,000
50
40
30
20
10
0
1000
100,000
754
2-79
Preliminary Information
MH88524
Figure 6 - Return Loss vs Junctor Resistance with MH88631 and MH88524
Figure 7 - MH88524 Application Circuit
550
60
50
40
30
20
10
800
TYPICAL
RETURN
LOSS
(dB)
JUNCTOR
RESISTANCE
JUN1
AGND
TX1
TX1
MH88524
600
650
700
750
850
900
950
JUNCTOR
RESISTANCE
(
)
RETURN LOSS
FREQ = 1000Hz
MH88631
RX1
TX1
TIP
RING
RX1
TX1
RX2
TX2
V
DD
AGND
V
EE
JUN2
JUN1
1
2
3
10
8
9
4
5
6
+5V
-5V
RECEIVE 1 INPUT
TRANSMIT 1 OUTPUT
RECEIVE 1 INPUT
TRANSMIT 2 OUTPUT
JUNCTOR1
INPUT/OUPUT
JUNCTOR 2
INPUT/OUTPUT
2-80
MH88524
Preliminary Information
Figure 8 - Application Circuit with MH88631, Crosspoint Switch and MH88524
Figure 9 - Application Circuit with MH88631, MH88510, Crosspoint Switch and MH88524
MH88631
MH88524
MH88631
MH88524
TO CO LINE
TIP 1
RING 1
TO CO LINE
TIP 2
RING 2
T
R
VX
VR
T
R
VX
VR
RX1
TX1
JUN1
AGND
JUN2
RX1
RECEIVE 1 INPUT
RX2
TX2
e.g.
MT8804
MT8816
etc.
Notes:
See MH88631, MT8804
and MT8816 data
sheets for device
details.
(1/2)
(1/2)
MH88631
MH88524
MH88510
TO CO LINE
TIP 1
RING 1
TO CO LINE
TIP 2
RING 2
T
R
VX
AGND
T
R
JUNC
VR
RX1
TX1
JUN1
AGND
RX1
RECEIVE 1 INPUT
e.g
MT8804
MT8816
etc.
Notes:
See MH88631, MT8804
and MT8816 data
sheets for device
details.
(1/2)
2-81
Preliminary Information
MH88524
Figure 10 - Application Circuit for Crosstalk Test
Figure 11 - Application Circuit with MT8840, MH88500 and MH88524
RX1
TX1
RX2
TX2
V
DD
AGND
V
EE
JUN2
JUN1
+5V
-5V
754
VOUT
JUN2
754
VIN RX1
VOUT
TX2
Notes
1) In addition to the above test circuit:
Apply VIN JUN1 and measure VOUT TX2 and VOUT JUN1.
Apply VIN JUN2 and measure VOUT TX1 and VOUT JUN1
Apply VIN RX2 and measure VOUT TX1 and VOUT JUN1.
CT (Crosstalk) calculation
Examples:
CT = 20xlog (VIN RX1/VOUT JUN2)
CT = 20xlog (VIN RX1/VOUT TX2)
2) All ground connections are star configured (i.e., single
point ground).
MH88524
Analog Signal Input
Digital Data Input
(2kHz max)
Digital Data Output
Analog Signal Output
32kHz ASK plus
Analog Input/Output
To Telephone Station
Set Input/Output
MH88524
MH88500
High Pass
Filter
Low Pass
Filter
MT8840
TXD1
RXD0
TX0
RX1
VSS
RX1
TX1
JUN1
AGND
JUNCTOR
TIP
RING
GND
Notes:
1) See MT8840 data sheet for device details.
2) See MH88500 data sheet for device details. Note that
this device is optional in this applications circuit.
3) High Pass Filter is typically 2nd order 15kHz
4) Low Pass Filter is typically 2nd order 4kHz
2-82
MH88524
Preliminary Information
Figure 12 - Mechanical Data
1.00 + 0.03
(25.4 + 0.0.08)
0.56+0.02
(14.2+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
9 10
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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