MT88E46 查看數據表（PDF） - Zarlink Semiconductor Inc

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MT88E46

Bellcore Compliant Calling Number Identification Circuit

Zarlink Semiconductor Inc 

Data Sheet

MT88E46

In Table 3 (talkoff results) column 3, the result was

obtained using pre-emphasized speech as both the near

end and far end speech sources. It is pessimistic, as

recognized in SR-TSV-002476, because in reality the pre-

emphasis originally imparted on the far end speech by the

far end CPE’s microphone would have been equalized by

the subscriber loop, so that at the near end CPE Tip/Ring

terminals the far end speech would have no pre-emphasis.

Table 3 column 4 shows the result for the same situation

as column 3 except that pre-emphasized speech was used

only as the near end speech source and normal speech was

used as the far end speech source, as allowed in SR-TSV-

002476.

In Table 3 column 5 and Table 4 column 4, the MT88E46

performance with a telephone hybrid / speech IC was

simulated during testing by attenuating the pre-

emphasized near end speech equally at all frequencies.

The actual performance will depend on the telephone

hybrid / speech IC design.

Functional Description

3 to 5 V Operation

The MT88E46 is designed to operate from a fixed voltage

power supply between 3 and 5 V nominal. A ±10%

variation from the nominal voltage is allowed. Its FSK

and CAS reject levels are proportional to Vdd. When

operated at Vdd equals 3 V ± 10%, to keep the FSK and

CAS reject levels as at 5 V ± 10%, and for optimal speech

immunity, the GS1 and GS2 op-amp gains should be

reduced from those of 5V. Gains for nominal Vdd’s

between 3 and 5 V can be obtained by interpolation

between the 3 V and 5 V values shown in Figure 9.

Input Configuration

The MT88E46 provides an input arrangement comprised

of two op-amps and a bias source (VREF). VREF is a low

impedance voltage source which is used to bias the op-

amp inputs at Vdd/2. The GS1 op-amp (IN1+, IN1-, GS1

pins) is for connecting to Tip and Ring. The GS2 op-amp

(IN2+, IN2-, GS2 pins) is for connecting to the receive

pair of the telephone hybrid or speech IC in the telephone

set application.

Either FSK demodulation or ‘on hook mode’ CAS

detection can be selected for the GS1 signal. Only ‘off

hook mode’ CAS detection is available for the GS2

signal. ‘On hook mode’ CAS detection at the GS1 op-amp

is intended for the MEI on hook CPE situation. ‘Off hook

mode’ CAS detection at the GS2 op-amp is intended for

the off hook CPE situation.

The feedback resistor connected between IN1- and GS1

can be used to adjust the Tip/Ring path input gain, and the

feedback resistor between IN2- and GS2 can be used to

adjust the hybrid / speech IC path input gain. When the

GS1 op-amp is selected, the GS2 signal is ignored. When

the GS2 op-amp is selected, the GS1 signal is ignored.

Either or both op-amps can be configured in the single

ended input configuration shown in Figure 3, or in the

differential input configuration shown in Figure 4.

IN+

C

RIN

IN-

RF

Passband Voltage Gain

AV = RF / RIN

Highpass Corner Frequency

f-3dB= 1/(2πRINC)

GS

VREF

Figure 3 - Single Ended Input Configuration

C1 R1

IN+

IN-

C2 R2

R3

GS

R4

R5

VREF

Differential Input Amplifier

C1 = C2

R2 = R1 (For unity gain R3= R1)

R4 = (R3R5) / (R3 + R5)

Passband Voltage Gain

(AVdiff) = R3/R1

Highpass Corner Frequency

f-3dB= 1/(2πR1C1)

Input Impedance

(ZINdiff) = 2 R12 + (1/ωC1)2

Figure 4 - Differential Input Configuration

In a telephone adjunct box application where there is no

hybrid or speech IC, if the GS2 gain with respect to Tip/

Ring is to be set to the same as that of GS1, the GS2 op-

amp can be connected as a voltage follower to the GS1

op-amp output as shown in Figure 5.

7

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