Le58083
Data Sheet
14. The supervision debounce time is set to 8 ms.
15. The chopper clock frequency is set to 256 kHz, but the chopper clock is turned off.
16. The E1 Multiplex state is turned off (E1 is Hi-Z) and the polarity is set for high-going pulses.
17. No signaling on the PCM highway (PCM/MPI mode).
SIGNAL PROCESSING
Overview of Digital Filters
Several of the blocks in the signal processing section are user programmable. These allow the user to optimize the performance
of the Le58083 Octal SLAC device for the system. Figure 23 shows the Le58083 Octal SLAC device signal processing and
indicates the programmable blocks.
The advantages of digital filters are:
■ High reliability
■ No drift with time or temperature
■ Unit-to-unit repeatability
■ Superior transmission performance
■ Flexibility
■ Maximum possible bandwidth for V.90 modems
Figure 23. Le58083 Octal SLAC Transmission Block Diagram
Cutoff
Transmit
Path
High Pass Filter (HPF)
(CTP)
VIN
*
Deci-
mator
Deci-
mator
LPF &
HPF
Com-
pressor
+
Digital
TX
AX
ADC
GX
*
X
*
TSA
GIN
TSA Loopback
(TLB)
AISN
Full
*
Z
B
*
*
Digital
Loopback
(FDL)
Cutoff Receive
Path (CRP)
*
Inter-
polator
Inter-
polator
Ex-
pander
+
+
AR DAC
GR
*
R
*
LPF
TSA
Digital
RX
VOUT
VREF
Lower Receive
Gain (LRG)
1 kHz Tone
(TON)
0
* programmable blocks
Two-Wire Impedance Matching
Two feedback paths on the Le58083 Octal SLAC device synthesize the two-wire input impedance of the SLIC device by providing
a programmable feedback path from VIN to VOUT. The Analog Impedance Scaling Network (AISN) is a programmable analog
gain of
−0.9375 • GIN to +0.9375 • GIN from VIN to VOUT. (See GIN in Electrical Characteristics, on page 13.) The Z filter is a
programmable digital filter providing an additional path and programming flexibility over the AISN in modifying the transfer
function from VIN to VOUT. Together, the AISN and the Z-Filter enable the user to synthesize virtually all required SLIC device
input impedances.
Frequency Response Correction and Equalization
The Le58083 Octal SLAC device contains programmable filters in the receive (R) and transmit (X) directions that may be
programmed for line equalization and to correct any attenuation distortion caused by the Z filter.
Transhybrid Balancing
The Le58083 Octal SLAC device’s programmable B filter is used to adjust transhybrid balance (MPI Commands 86/87h and 96/
97h, GCI Commands COP 5 and COP 8). The filter has a single pole IIR section (BIIR) and an eight-tap FIR section (BFIR), both
operating at 16 kHz.
38
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
