CS61305A-IL1 Cirrus Logic, Inc., CS61305A-IL1 Datasheet - Page 10

• Manufacturer Part Number: CS61305A-IL1
• Description: T1/E1 line interface
• Manufacturer: Cirrus Logic, Inc.

Transmitter
The transmitter takes digital T1 or E1 input data
and drives appropriately shaped bipolar pulses
onto a transmission line. The transmit data (TPOS
& TNEG or TDATA) is supplied synchronously
and sampled on the falling edge of the input
clock, TCLK.
Either T1 (DSX-1 or Network Interface) or E1
CCITT G.703 pulse shapes may be selected.
Pulse shaping and signal level are controlled by
"line length select" inputs as shown in Table 3.
The output options in Table 3 are specified with a
1:1.15 transmitter transformer turns ratio for T1
and a 1:1 turns ratio for E1 without external se-
ries resistors. Other turns ratios may be used if
approriate resistors are placed in series with the
TTIP and TRING pins. Table A1 in the applica-
tions section lists other combinations which can
be used to provide transmitter impedance match-
ing.
For T1 DSX-1 applications, line lengths from 0 to
655 feet (as measured from the transmitter to the
DSX-1 cross connect) may be selected. The five
partition arrangement in Table 3 meets ANSI
T1.102-1993 and AT&T CB-119 requirements
when using #22 ABAM cable. A typical output
pulse is shown in Figure 8. These pulse settings
can also be used to meet CCITT pulse shape re-
quirements for 1.544 MHz operation.
For T1 Network Interface applications, two addi-
tional options are provided. Note that the optimal
pulse width for Part 68 (324 ns) is narrower than
the optimal pulse width for DSX-1 (350 ns). The
CS61305A automatically adjusts the pulse width
based upon the "line length" selection made.
The E1 G.703 pulse shape is supported with line
length selections LEN2/1/0 = 0/0/0 and 0/0/1.
The pulse width will meet the G.703 pulse shape
template shown in Figure 9, and specified in Ta-
ble 4.
10
The CS61305A transmitter provides short-circuit
current limiting protection and meets OFTEL
OTR-001 short-circuit current limiting require-
ments for E1 applications.
The CS61305A will detect a static TCLK, and
will force TTIP and TRING low to prevent trans-
mission when data is not present. When any
transmit control pin (TAOS, LEN0-2 or LLOOP)
is toggled, the transmitter outputs will require ap-
proximately 22 bit periods to stabilize. The
transmitter will take longer to stabilize when
RLOOP is selected because the timing circuitry
must adjust to the new frequency.
-0.5
Figure 8. Typical Pulse Shape at DSX-1 Cross Connect
LEN2 LEN1 LEN0
1.0
0.5
0
0
1
1
1
1
0
0
0
0
0
NORMALIZED
AMPLITUDE
1
0
0
1
1
0
0
1
1
Table 3. Line Length Selection
250
1
0
1
0
1
0
1
0
1
PULSE SHAPE
FCC PART 68, OPT. A
OUTPUT
120 twisted-pair
TIME (nanoseconds)
Option Selected
500
ANSI T1.403
133-266 ft
266-399 ft
399-533 ft
533-655 ft
75 coax
0-133 ft
CS61305A
ANSI T1.102,
AT&T CB 119
SPECIFICATIONS
750
CCITT G.703
Application
(AT&T 600B
DS157PP3
or 600C)
Interface
Network
DSX-1
ABAM
E1
1000