Datasheet MT89761 Datasheet (MITEL)

Page 1
4-93
Features
Compatible with th e MH8 9760B
Transmit equal izer an d 6d B loop ar oun d circ uit
6dB pad for easier loopback testing
Programmable for varying degrees of equalizat io n
The MH89761 is a programmable transmit equalizer for use with a T1 line interface, specifically the MH89760B. The MH89761 contains a three setting transmit equalizer, and a 6 dB pad for external loop around. The input and output impedance of the circuit is 100. The device is fabricated in thick film hybrid technology and is 2 inches high by 0.5 inches wide. The MH89761 is designed to drive 22 gauge twisted pair from the multiplex equipment to the crossconnect point. Figure 1 shows how the MH89761 is connected to the transmit side of a T1 interface.
Figure 1 - Connection Diagram
MH89761
TR1
MH89760B
OUTA
OUTB
RxT
RxR
+12V
L2
C2
TR2
1:
1:
1:
:0.5
R1
L1
C1
••
S1 S2 S3
S4 S5
S6 S7
EIT EIR
EA EB
EC SW
RCLT RCHT
RCLR RCHR
Ti Ri
TxT
TxR
TL
RL
R1 = 150 C1 = .01µF C2 = .47µF L1 = 33µH L2 = 33µH
1:
1:
Ordering Information -40°C to 85°C
MH89761 20 Pin SIP Hybrid
TL TL
TI
Ri RL RL
TxT
EIT
EA
L1
EB
EC
L2
RCHT
RCLT
TxR
EIR
SW
RCHR
RCLR
Pin Connections
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
ISSUE 4 May 1995
MH89761
T1 Transmit Equalizer
Advance Information
Page 2
4-94
MH89761 Advance Information
Applications
The MH89761 can be connected to the MH89760B as illustrated in Figure 1. All pins on the MH89761 not shown connected in Figure 1 should be left open. The internal circuit of the equalizer is shown in Figure 2. The MH89761 has two separate circuits; a 6dB pad and an equalizer.
Ti and Ri are inputs to the 6dB pad on the device. The outputs of the pad are brought out on TL and RL. The 6dB pad is provided to loopback the transmit signal back to the receive without altering the equalizer settings. The 4 pole double throw relay shown in Figure 1 per m its connection of the output of the transformer TR1 to either the equalizer or the fixed 6dB pad. For normal operation and transmission out to the line, the transformer should be connected to the equalizer inputs EIT and EIR. Enabling the relay will switch the connection through the 6dB pad for loopback diagnostics.
The MH89761 is designed to accept output from the secondary of the T1 transmit transformer and condition it for transmission over twisted pair. The seven switche s (S1 to S7) permit con fi gura tion o f the equalizer for different line lengths. The pulse amplitude at the secondary of TR1 is approximately 6V. Passing this signal through the equalizer with zero line length setting on the switches will result in attenuation of the pulse by 6dB. This will ensure that the pulse fits in the tem plate shown in Figure 3 a nd meets DSX-1
requirements. By switching in different C and L components, the frequency and phase response of the equalizer can be altered as shown in Figures 4 and 5. Note that the circuit attenuates lower frequencies more than higher frequencies. Consequently, when a pulse is passed through the equalizer, lower frequency componen ts in the signal are a tte nu ated m or e tha n higher fre quency components. The intention is to compensate for the attenuation properties of twisted pair cable, which tends to attenuate higher frequencies more than lower frequencies. The net result is that a pre­equalized pulse will meet DSX pulse requirements after traversing a specific length of cable.
The cable length indicated along withthe equalizer switch settings in Figure 4 are specific to 22 awg ABAM cable interfaced to an MH89760B equipped with a Filtran➁ TFS2573 transformer. Different equalizer settings may be more appropriate for other cable and transformer types. Figure 6 shows the generic switch settings for different levels of equalization.
Reference: ANSI T1.102 - 1987, Section 2.2
Manufacturer: Filtran Ltd.
(613) 226-1626
Figure 2 - 6dB Pad and Equalizer Pin
Ti
50
6dB Pad
S5
S4
4870pF
2150pF
TxT
EiT
EQUALIZER
TL
Ri
RL
50 50
50 50
100
50
200
50
50 50
100
12
S1
S2
S3
10µH
22µH
50
50
50
200
EiR
TxR
2150pF
S6
S7
4870pF
27
••
••
390
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Advance Information MH89761
Figure 3 - DSX -1 Line Pulse Template (Refer ence : ANSI T 1.102-1 987 )
Figure 4 - Typical Frequency Response of the Equalizers
AAA
AAAA
t1t
2
t
3
t
4
t
5t6
t
8
t
9
t
10
t
11
t
12t13
t
7
115% 105%
95% 90%
80%
50%
5%
-7%
-5%
-20%
-45%
Nominal
Pulse Shape
SYMBOL TIME
t
1
100 ns
t
2
75 ns
t
3
175 ns
t
4
50 ns
t
5
100 ns
t
6
100 ns
t
7
75 ns
t
8
50 ns
t
9
50 ns
t
10
375 ns
t
11
150 ns
t
12
130 ns
t
13
175 ns
Note 1: Template is not to scale
0
1
2
3
4
5
6
A T T E N U A T I O N
d B
100K 200K 500K 1000K 2000K 5000K 10M 20M 50M 100M
Frequency (Hz)
Note: 100Resistive Load
LONG
MEDIUM
SHORT
Short
0-150’
Medium
150-450’
Long
450-65 5’
S1 CLOSE OPEN OPEN S2 OPEN CLOSE OPEN S4 OPEN OPEN CL OSE S4 OPEN CLOS E OPEN S5 OPEN OPEN CL OSE S6 OPEN CLOS E OPEN S7 OPEN OPEN CL OSE
Equalizer settings
Note: The equalizer shown here is optimum for 22 gauge ABAM cable and Filtran TFS2573 transformer. The distance settings are approximate and may vary with cable and transformer type
Attenuation Versus Frequency
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A
Page 4
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MH89761 Advance Information
Figure 5 - Typical Phase Response of the Equalizers
Figure 6 - Switch Settings for Different Levels of Equalization
24
20
16
12
8
4
0
100K 200K 500K 1000K 2000K 5000K 10M 20M 50M 100M
Frequency (Hz)
Phase Angle Versus Frequenc y
LONG
MEDIUM
SHORT
Note: 100 Resistive Load
D E G R E E S
- = SWITCH OPENED X = SWITCH CLOSED
S1
S2 S3 S4
S5 S6 S7
X
X
X
XXX
XX
X
XXX
XXX
XX
XXX
XXX
XXX
XXX
XXXXX X
INCREASING EQUALI ZATION
MAX. EQUALIZATIO N
Long Cables
NO EQUALIZATION
Short Cables
-
-
-
-
-
-
-
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X
-
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Page 5
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Advance Information MH89761
Figure 7 - Mechanical Data
AA
0.03 Ma x.
(0.8 Max.)
Side View
Pin 1
0.01 0 +
0.00 2
(0.25 +
0.05)
0.2 Max.
(5.1 Max.)
0.40 +
0.02
(10.2 +
0.5)
0.18 +
0.02
(4.6 +
0.5)
0.05 +
0.02
(1.3 + 0.5 )
0.020 + 0.005 (0.51 + 0.13)
0.10 + 0.01 (2.5 + 0.2)
Front View
Notes:
1) Not to scale.
2) Dimensions in inches
3) (Dimensions in millimeters) * Dimension to center of pin
2.00 + 0.02
(50.8 + 0.5)
1 5 10 15 20
15
*
0.05 ± 0.01 (1.3 ± 0.3)
*
Page 6
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MH89761 Advance Information
NOTES:
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