MC33121 Datasheet, PDF (27/32 Pages) Motorola, Inc – LOW VOLTAGE SUBSCRIBER LOOP INTERFACE CIRCUIT

CIRCUIT PERFORMANCE
The following three circuits are presented as typical ap-
plication examples, and the accompanying graphs indicate
their measured performance. The first circuit (Figure 46) has
a 600 Ω pure resistance as the AC load. The second circuit
(Figures 47) has as an AC load a 900 Ω resistor in series with
a 2.16 µF capacitor. The third circuit (Figure 48) has as an
AC load, a complex network composed of an 820 Ω resistor
in parallel with 0.115 µF, and those in series with a 220 Ω re-
sistor. In the graphs of Figures 49 – 51, RL = Return Loss,
THR = Transhybrid Rejection, GTX = Transmit Gain, GRX =
Receive Gain.
20 _VCC
19 _EP
0.01
TIP ^VEE
RAC
600 Ω
VL _RING
MJD253 18 _BP
1.0 k, 2%
100
9.1 k
17 _CP
16 _TSI
9.1 k
5 _RSI
1.0 k, 2%
0.01 ¹⁰⁰
4 _CN
MJD243 3 _BN
VEE
2 _EN
– 28 V
1 _VEE
0.1
MC33121
VDD ¹⁵
PDI ¹²
ST1 ¹³
+ 5.0 V
0.1
5.0 µF
ST2/PDI
ST1
VDG ¹⁴
VAG ⁹
RXI ¹⁰
RFO ⁸
TXO ¹¹
4.7 k
1.0 µF
CF ^{7 300}
VQB ^{6 20}
30.6 k
20.3 k 600
0.005
15.8 k
600
10 k
1.0 µF
1.0 µF
10 µF
31.6 k
–
+
Figure 46. 600 Ω System
RECEIVE
IN (VRX)
TRANSMIT
OUT (VTX)
20 _VCC
19 _EP
0.01
RAC
900 Ω
2.16 µF
TIP ^VEE
VL _RING
0.01
VEE
MJD253 18 _BP
1.0 k, 2%
100
9.1 k
17 _CP
16 _TSI
9.1 k
5 _RSI
1.0 k, 2%
100
4 _CN
MJD243 3 _BN
2 _EN
– 28 V
1 _VEE
0.1
MC33121
VDD ¹⁵
PDI ¹²
ST1 ¹³
+ 5.0 V
0.1
5.0 µF
ST2/PDI
ST1
VDG ¹⁴
VAG ⁹
RXI ¹⁰
RFO ⁸
TXO ¹¹
4.7 k
62 nF
CF ^{7 300}
VQB ^{6 20}
45.9 k ^{42 nF}
31.2 k
10 k
1.0 µF
10 µF
31.6 k
1.0 µF
31.6 k
–
+
RECEIVE
IN (VRX)
TRANSMIT
OUT (VTX)
MOTOROLA
Figure 47. 900 Ω and 2.16 µF System
MC33121
27