Datasheet

DS2148/DS21Q48
49 of 73
Figure 7-1. Basic Interface
NOTES:
1) All resistor values are ±1%.
2) In E1 applications, the Rt resistors are used to increase the transmitter return loss (Table 7-1). No return loss is required for T1
applications.
3) The Rr resistors should be set to 60Ω each if the internal receive-side termination feature is enabled. When this feature is disabled, Rr
= 37.5Ω for 75Ω, 60Ω for 120Ω E1 systems, or 50Ω for 100Ω T1 lines.
4) See Table 7-1 and Table 7-2 for the appropriate transmit transformer turns ratio (N).
RTIP
RRING
TTIP
TRING
Receive
Line
N:1
(larger winding
toward the network)
DS2148
0.47µF
(non
polarized)
V
DD
(21)
V
SS
(22)
0.1µF
V
DD
(36)
V
SS
(35)
0.1µF
+V
DD
0.01µF
2.048MHz
(this clock can also
be 1.544MHz for T1
only applications)
MCLK
1:1
0.1µF
R
r
R
r
Rt
Rt
Transmit
Line
10µF
10µF