LTC1544IG#TRPBF Linear Technology, LTC1544IG#TRPBF Datasheet - Page 13

• Manufacturer Part Number: LTC1544IG#TRPBF
• Description: IC TXRX SOFTWARE SELECTBL 28SSOP
• Manufacturer: Linear Technology
• Type: Transceiverr

Specifications of LTC1544IG#TRPBF

• Number Of Drivers/receivers: 4/4
• Voltage - Supply: 4.75 V ~ 5.25 V
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Protocol: -

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 20.
APPLICATIONS
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.
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.
Figure 20. V.35 Driver Using the LTC1344A
V.35 DRIVER
U
LTC1344A
INFORMATION
U
124
C1
100pF
ON
W
S2
S1
ON
51.5
51.5
15 . For the
U
1544 F20
A
B
C
to
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.
DTE vs DCE Operation
The DCE/DTE pin acts as an enable for Driver 3/Receiver
1 in the LTC1543, and Driver 3/Receiver 1 and Driver 4/
Receiver 4 in the LTC1544. The INVERT pin in the LTC1544
allows the Driver 4/Receiver 4 enable to be high or low true
polarity.
5V
C3
1 F
DD
and V
EE
C1
1 F
C4
1 F
capacitor C5 should be a minimum of
Figure 21. Charge Pump
3
2
1
4
EE
V
C1
C1
V
DD
CC
+
–
as shown in Figure 21. A voltage
LTC1543
EE
. Four 1 F surface mounted
GND
DD
C2
C2
V
EE
+
–
and a voltage inverter
28
27
26
25
+
LTC1544
1544 F21
C2
1 F
C5
3.3 F
13