IDT82P2816 Datasheet, PDF (34/146 Pages) Integrated Device Technology – 16(+1) Channel High-Density T1/E1/J1 Line Interface Unit

IDT82P2816
16(+1) CHANNEL HIGH-DENSITY T1/E1/J1 LINE INTERFACE UNIT
3.3.5 LINE DRIVER
The Line Driver can be set to High-Z for protection or in redundant
applications.
The following two ways will set the Line Driver to High-Z:
• Setting the OE pin to low will globally set all the Line Drivers to
High-Z;
• Setting the OE bit (b6, TCF0,...) to ‘0’ will set the corresponding
Line Driver to High-Z.
By these ways, the functionality of the internal circuit is not affected
and TTIPn and TRINGn will enter High-Z state immediately.
3.3.5.1 Transmit Over Current Protection
The Line Driver monitors the Transmit Over Current (TOC) on the
line interface. When TOC is detected, the driver’s output (i.e., output on
TTIPn/TRINGn) is determined by the THZ_OC bit (b4, TCF0,...). If the
THZ_OC bit (b4, TCF0,...) is ‘0’, the driver’s output current (peak to
peak) is limited to 100 mA; if the THZ_OC bit (b4, TCF0,...) is ‘1’, the
driver’s output will enter High-Z. TOC is indicated by the TOC_S bit (b4,
STAT0,...). A transition from ‘0’ to ‘1’ on the TOC_S bit (b4, STAT0,...) or
any transition (from ‘0’ to ‘1’ or from ‘1’ to ‘0’) on the TOC_S bit (b4,
STAT0,...) will set the TOC_IS bit (b4, INTS0,...) to ‘1’, as selected by the
TOC_IES bit (b4, INTES,...). When the TOC_IS bit (b4, INTS0,...) is ‘1’,
an interrupt will be reported by INT if not masked by the TOC_IM bit (b4,
INTM0,...).
TOC may be indicated by the TMFn pin. Refer to Section 3.5.7.2
TMFn Indication for details.
Table-15 Impedance Matching Value in Transmit Differential Mode
3.3.6 T_X TERMINATION
The transmit line interface supports Transmit Differential mode and
Transmit Single Ended mode, as selected by the T_SING bit (b3,
TCF0,...). In Transmit Differential mode, both TTIPn and TRINGn are
used to transmit signals to the line side. In Transmit Single Ended mode,
only TTIPn is used to transmit signal.
The line interface can be connected with T1 100 Ω, J1 110 Ω or E1
120 Ω twisted pair cable or E1 75 Ω coaxial cable.
The transmit impedance matching is realized by using internal
impedance matching or external impedance matching for each channel
in different applications.
3.3.6.1 Transmit Differential Mode
In Transmit Differential mode, different applications have different
impedance matching. For T1/J1 applications, only Internal Impedance
Matching is supported. For E1 applications, both Internal and External
Impedance Matching are supported.
Internal Impedance Matching circuit uses an internal programmable
resistor (IM) only.
External Impedance Matching circuit uses an external resistor (Rt)
only.
A twisted pair cable can be connected with a 1:2 (step up) trans-
former or without a transformer (transformer-less), while a coaxial cable
must be connected with a 1:2 transformer.
The T_TERM[2:0] bits (b2~0, TCF0,...) should be set according to
different cable conditions, whether a transformer is used, and what kind
of Impedance Matching is selected.
Table-15 lists the recommended impedance matching value in
different applications. Figure-15 to Figure-17 show the connection for
one channel in different applications.
The transformer-less connection will offer a termination option with
reduced cost and board space. However, the waveform amplitude is not
standard compliant, and surge protection and common mode depres-
sion should be enhanced depending on equipment environment..
Cable Condition
T1 100 Ω twisted pair (with transformer)
J1 110 Ω twisted pair (with transformer)
E1 120 Ω twisted pair (with transformer), PULS[3:0]=0001
E1 75 Ω coaxial (with transformer), PULS[3:0]=0000
T1 100 Ω twisted pair (transformer-less)
J1 110 Ω twisted pair (transformer-less)
E1 120 Ω twisted pair (transformer-less), PULS[3:0]=0001
Internal Impedance Matching
T_TERM[2:0]
Rt
000
001
010
011
0
100
101
110
External Impedance Matching
T_TERM[2:0]
Rt
(not supported)
111
10 Ω
(not supported)
Functional Description
34
January 11, 2007