MT88E45
IN+
Data Sheet
C
R
IN
IN-
Voltage Gain
(A
V
) = R
F
/ R
IN
Highpass Corner Frequency
f
-3dB
= 1/(2πR
IN
C)
R
F
GS
V
REF
Figure 3 - Single Ended Input Configuration
C1
R1
IN+
IN-
C2
R4
R5
GS
R3
R2
Differential Input Amplifier
C1 = C2
R1 = R4 (For unity gain R5= R4)
R3 = (R2R5) / (R2 + R5)
Voltage Gain
Highpass Corner Frequency
(A
V
diff) = R5/R1
f
-3dB
= 1/(2πR1C1)
Input Impedance
(Z
IN
diff) = 2
R1
2
+ (1/ωC)
2
V
REF
Figure 4 - Differential Input Configuration
CAS Detection
In North America, CAS is used in off-hook signalling only. In Europe (ETSI) it is used in off-hook signalling, and by
BT in both on and off-hook signalling. ETSI calls it the Dual Tone Alerting Signal (DT-AS). Although the ETSI on-
hook standard contains a DT-AS specification, BT is the only administration known to employ CAS in on-hook
signalling. (BT calls it Tone Alert Signal.) The CAS/DT-AS characteristics are summarized in Table 3.
2130 Hz and 2750 Hz
CAS/DT-AS Characteristics
Frequency Tolerance
Signal Level (per tone)
Reject Level (per tone)
Maximum Twist (V
2130Hz
/V
2750Hz
)
Bellcore
(Off-hook only)
+/-0.5%
-14 to -32 dBm
d
-45 dBm
+/-6 dB
a
ETSI
(Off-hook)
+/-0.5%
-9.78 to -32.78 dBm
(-12 to -35 dBV
e
)
b
BT
c
(Off-hook = ‘Loop State’)
(On-hook = ‘Idle State’)
Off-hook: +/-0.6%
On-hook: +/-1.1%
+0.22 to -37.78 dBm
(-2 to -40 dBV)
On-hook: -43.78 dBm
(-46 dBV)
+/-6 dB
+/-7 dB
8
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
