Datasheet

DS21348/DS21Q348
51 of 76
7.4 G.703 Synchronization Signal
The DS21348 can receive a 2.048MHz square-wave synchronization clock as specified in Section 13 of
ITU G.703(10/98). To use the DS21348 in this mode, set the Receive Synchronization Clock Enable
(CCR5.3) = 1. The DS21348 can also transmit the 2.048MHz square-wave synchronization clock as
specified in Section 10 of G.703. To transmit the 2.048MHz clock, set the Transmit Synchronization
Clock Enable (CCR5.2) = 1.
Table 7-1. Line Build-Out Select for E1 in Register CCR4 (ETS = 0)
L2 L1 L0
V
DD
(V)
APPLICATION N
RETURN LOSS
(dB)
Rt (Ω)
0 0 0 3.3
75Ω normal
1:2 N.M. 0
0 0 1 3.3
120Ω normal
1:2 N.M. 0
1 0 0 3.3
75Ω with high return loss
1:2 21 6.2
1 0 1 3.3
120Ω with high return loss
1:2 21 11.6
Note: See Figure 7-1, Figure 7-2, and Figure 7-3. N.M. = Not meaningful.
Table 7-2. Line Build-Out Select for T1 in Register CCR4 (ETS = 1)
L2 L1 L0
V
DD
(V)
APPLICATION N
RETURN LOSS
(dB)
Rt (Ω)
0 0 0 3.3
DSX-1 (0 to 133 feet)/
0dB CSU
1:2 N.M. 0
0 0 1 3.3 DSX-1 (133 to 266 feet) 1:2 N.M. 0
0 1 0 3.3 DSX-1 (266 to 399 feet) 1:2 N.M. 0
0 1 1 3.3 DSX-1 (399 to 533 feet) 1:2 N.M. 0
1 0 0 3.3 DSX-1 (533 to 655 feet) 1:2 N.M. 0
1 0 1 3.3 -7.5dB CSU 1:2 N.M. 0
1 1 0 3.3 -15dB CSU 1:2 N.M. 0
1 1 1 3.3 -22.5dB CSU 1:2 N.M. 0
Note: See Figure 7-1, Figure 7-2, and Figure 7-3. N.M. = Not meaningful.
Table 7-3. Transformer Specifications for 3.3V Operation
SPECIFICATION RECOMMENDED VALUE
Turns Ratio 3.3V Applications 1:1 (receive) and 1:2 (transmit) ±2%
Primary Inductance
600µH minimum
Leakage Inductance
1.0µH maximum
Intertwining Capacitance 40pF maximum
Transmit Transformer DC Resistance
Primary (Device Side)
Secondary
1.0Ω maximum
2.0Ω maximum
Receive Transformer DC Resistance
Primary (Device Side)
Secondary
1.2Ω maximum
1.2Ω maximum