LTC1543IG Linear Technology, LTC1543IG Datasheet - Page 13

• Manufacturer Part Number: LTC1543IG
• Description: IC TXRX SOFTWARE SELECTBL 28SSOP
• Manufacturer: Linear Technology
• Type: Transceiverr

Specifications of LTC1543IG

• Number Of Drivers/receivers: 3/3
• Voltage - Supply: 4.75 V ~ 5.25 V
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Protocol: -

APPLICATIO S I FOR ATIO
impedance of the receiver is placed in parallel with the T
network termination, but does not affect the overall input
impedance significantly.
The generator differential impedance must be 50
150 and the impedance between shorted terminals (A
and B) and ground C must be 150
generator termination, switches S1 and S2 are both on and
the top side of the center resistor is brought out to a pin so
it can be bypassed with an external capacitor to reduce
common mode noise as shown in Figure 21.
Any mismatch in the driver rise and fall times or skew in
the driver propagation delays will force current through
the center termination resistor to ground, causing a high
frequency common mode spike on the A and B terminals.
The common mode spike can cause EMI problems that are
reduced by capacitor C1 which shunts much of the com-
mon mode energy to ground rather than down the cable.
Figure 21. V.35 Driver Using the LTC1344A
V.35 DRIVER
U
LTC1344A
U
124
C1
100pF
W
ON
S2
S1
ON
51.5
51.5
15 . For the
U
1543 F21
A
B
C
to
No-Cable Mode
The no-cable mode (M0 = M1 = M2 = 1) is intended for the
case when the cable is disconnected from the connector.
The charge pump, bias circuitry, drivers and receivers are
turned off, the driver outputs are forced into a high
impedance state, and the supply current drops to less than
200 A.
Charge Pump
The LTC1543 uses an internal capacitive charge pump to
generate V
doubler generates about 8V on V
generates about – 7.5V for V
tantalum or ceramic capacitors are required for C1, C2, C3
and C4. The V
3.3 F. All capacitors are 16V and should be placed as close
as possible to the LTC1543 to reduce EMI.
Receiver Fail-Safe
All LTC1543/LTC1544 receivers feature fail-safe opera-
tion in all modes. If the receiver inputs are left floating or
shorted together by a termination resistor, the receiver
output will always be forced to a logic high.
5V
DD
C3
1 F
and V
EE
C1
1 F
C4
1 F
capacitor C5 should be a minimum of
Figure 22. Charge Pump
EE
3
2
1
4
V
C1
C1
V
as shown in Figure 22. A voltage
DD
CC
+
–
LTC1543
EE
. Four 1 F surface mounted
DD
GND
C2
C2
V
and a voltage inverter
EE
+
–
28
27
26
25
LTC1543
+
1543 F22
C2
1 F
C5
3.3 F
sn1534 1543fas
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