Datasheet MT89761 Datasheet (MITEL)

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

Description

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 100Ω. 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:

: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 = 150Ω C1 = .01µF C2 = .47µF L1 = 33µH L2 = 33µH

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

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

➀

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.

➀

Reference: ANSI T1.102 - 1987, Section 2.2

➁

Manufacturer: Filtran Ltd.

(613) 226-1626

Figure 2 - 6dB Pad and Equalizer Pin

Ti

50Ω

6dB Pad

S5

S4

4870pF

2150pF

TxT

EiT

EQUALIZER

TL

Ri

RL

50Ω 50Ω

100Ω

50Ω

200Ω

50Ω

50Ω 50Ω

100Ω

12Ω

S1

S2

S3

10µH

22µH

50Ω

200Ω

EiR

TxR

2150pF

S6

S7

4870pF

27Ω

•

••

•

••

•

390Ω

4-95

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: 100Ω Resistive 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

AAAA

A

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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: 100Ω Resistive Load

D E G R E E S

- = SWITCH OPENED X = SWITCH CLOSED

S1

S2 S3 S4

S5 S6 S7

X

XXX

XX

X

XXX

XX

XXX

XXXXX X

INCREASING EQUALI ZATION

MAX. EQUALIZATIO N

Long Cables

NO EQUALIZATION

Short Cables

-

X

-

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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)

*

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MH89761 Advance Information

NOTES: