MT88E46AS Zarlink, MT88E46AS Datasheet - Page 7

• Manufacturer Part Number: MT88E46AS
• Description: Caller ID CMOS 3.58MHz 3.3V/5V 20-Pin SOIC Tube
• Manufacturer: Zarlink

Specifications of MT88E46AS

• Package: 20SOIC
• Telecommunication Standards Supported: Bellcore GR-30-CORE|SR-TSV-002476|TIA/EIA-716|TIA/EIA-777
• Fabrication Technology: CMOS
• Maximum Data Rate: 1.212 KBd
• Typical Operating Supply Voltage: 3.3|5 V
• Typical Supply Current: 4.3 mA
• Minimum Operating Temperature: -40 °C
• Maximum Operating Temperature: 85 °C
• Operating Frequency: 3.58 MHz

Data Sheet
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 (V
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.
REF
). V
REF
is a low
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 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.
Passband Voltage Gain
A
Highpass Corner Frequency
f
Differential Input Amplifier
Passband Voltage Gain
(A
C1 = C2
R2 = R1 (For unity gain R3= R1)
R4 = (R3R5) / (R3 + R5)
Input Impedance
(Z
-3dB
V
Figure 3 - Single Ended Input Configuration
V
IN
Figure 4 - Differential Input Configuration
= R
diff) = R3/R1
diff) = 2
= 1/(2πR
C
C1
C2
F
/ R
IN
IN
R1
R2
R
R4
IN
C)
R
1
2
+ (1/ωC
R
F
1
R5
)
2
Highpass Corner Frequency
f
-3dB
R3
= 1/(2πR
GS
IN+
IN-
V
V
GS
IN+
IN-
REF
REF
MT88E46
1
C
1
)
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