LT1711IMS8 Ver la hoja de datos (PDF) - Linear Technology
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LT1711IMS8 Datasheet PDF : 12 Pages
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APPLICATIO S I FOR ATIO
Q
50k
VIN
+
LT1711
50Ω
VIN
+
Q
50Ω
VIN+
–
50k
50Ω
LT1711
Q
VREF
–
VIN– 50Ω
V+ = 5V
Q
V– = –5V
VHYST = 5mV
(ALL 3 CASES)
Figure 2. Various Configurations for Introducing Hysteresis
LT1711/LT1712
100k
+
LT1711
–
100k
Q
Q
171112 F02
TYPICAL APPLICATIO S
Simultaneous Full Duplex 75Mbaud Interface
with Only Two Wires
The circuit of Figure 3 shows a simple, fully bidirectional,
differential 2-wire interface that gives good results to
75Mbaud, using the LT1712. Eye diagrams under condi-
tions of unidirectional and bidirectional communication
are shown in Figures 4 and 5. Although not as pristine as
the unidirectional performance of Figure␣ 4, the perfor-
mance under simultaneous bidirectional operation is still
excellent. Because the LT1712 input voltage range ex-
tends 100mV beyond both supply rails, the circuit works
with a full ±3V (one whole VS up or down) of ground
potential difference.
The circuit works well with the resistor values shown, but
other sets of values can be used. The starting point is the
characteristic impedance, ZO, of the twisted-pair cable.
The input impedance of the resistive network should
match the characteristic impedance and is given by:
RIN
=
2
•
RO
•
RO
R1||(R2 + R3)
+ 2 • [R1||(R2 +
R3)]
750k
3V
4
2
14
RxD
1/2
LE LT1712 1
13 16
3
15
750k
100k
3V
49.9Ω 7 +
5
11
TxD
49.9Ω
1/2
8
LT1712
– LE
10
12
6
9
100k
R2A
2.55k
R3A
124Ω
R3B
124Ω
R2B
2.55k
3V
R1A
499Ω
ROA
140Ω
R1B
499Ω
6-FEET
TWISTED PAIR
ZO ≈ 120Ω
DIODES: BAV99
×4
3V
R1C
499Ω
ROB
140Ω
R1D
499Ω
R2C
2.55k
R3C
124Ω
R3D
124Ω
R2D
2.55k
750k
3V
2+
4
14
1/2
1
LT1712 LE
–
16
13
RxD
15
3
750k
100k
3V
5
11
7 49.9Ω
1/2
LT1712 8 49.9Ω TxD
12 6 LE
10
9
100k
171112 F03
Figure 3. 75Mbaud Full Duplex Interface on Two Wires
9
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