IDT82P2284 Datasheet, PDF (26/384 Pages) Integrated Device Technology – Quad T1/E1/J1 Long Haul / Short Haul Transceiver

IDT82P2284
QUAD T1/E1/J1 LONG HAUL / SHORT HAUL TRANSCEIVER
3.2 RECEIVER IMPEDANCE MATCHING
The receiver impedance matching can be realized by using internal
impedance matching circuit or external impedance matching circuit.
When the R_TERM[2] bit is ‘0’, the internal impedance matching
circuit is enabled. 100 Ω, 110 Ω, 75 Ω or 120 Ω internal impedance
matching circuit can be selected by the R_TERM[1:0] bits.
When the R_TERM[2] bit is ‘1’, the internal impedance matching
circuit is disabled, and different external resistors should be used to real-
ize different impedance matching.
Figure 2 shows the appropriate components to connect with the
cable for one link. Table 3 lists the recommended impedance matching
value for the receiver.
Table 3: Impedance Matching Value For The Receiver
Cable
Configuration
75 Ω (E1)
120 Ω (E1)
100 Ω (T1)
110 Ω (J1)
Internal Termination
R_TERM[2:0]
000
001
010
011
R_R
120 Ω
External Termination
R_TERM[2:0]
1XX
R_R
75 Ω
120 Ω
100 Ω
110 Ω
A
RX Line
B
TX Line
• ^1:1•
•^2:1•
VDDAR
D8
•
· _RTIP
D7
RR ^VDDAR
D6
• _D5 ^· _VDDAX RRING
RT
D4
· TTIP
D3
Cp
VDDAX
D2
· TRING
RT
D1
VDDAR
0.1µF
GNDA
•
VDDAX
0.1µF
GNDA
•
3.3 V
68µF ¹
3.3 V
68µF ¹
Note: 1. Common decoupling capacitor
2. Cp 0-560 (pF)
3. D1 - D8, Motorola - MBR0540T1;
International Rectifier - 11DQ04 or 10BQ060
Figure 2. Receive / Transmit Line Circuit
In short haul applications, after the data stream passes through the
receive internal impedance circuitry, the non-intrusive monitoring can be
performed between two devices. The monitored link of one device is in
normal operation, and the monitoring link of the other device taps the
monitored one through a high impedance bridging circuit (refer to
Figure 3 and Figure 4). Because of the high resistance bridging circuit,
the signal arriving at the RTIPn/RRINGn of the monitoring link is dramat-
ically attenuated. To compensate this attenuation, the Monitor Gain can
be used to boost the signal by 22 dB, 26 dB and 32 dB selected by the
MG[1:0] bits. For normal operation, the Monitor Gain should be set to 0
dB, i.e. the Monitor Gain of the monitored link should be 0 dB.
Functional Description
15
March 22, 2004