LTC2844CG#PBF Linear Technology, LTC2844CG#PBF Datasheet - Page 14

• Manufacturer Part Number: LTC2844CG#PBF
• Description: IC TXRX 3.3V MULTIPROTCOL 28SSOP
• Manufacturer: Linear Technology
• Type: Transceiverr

Specifications of LTC2844CG#PBF

• Number Of Drivers/receivers: 4/4
• Protocol: Multiprotocol
• Voltage - Supply: 3.3V
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS
LTC2844
V.35 Interface
A typical V.35 balanced interface is shown in Figure 18. A
V.35 differential generator with outputs A and B with
ground C is connected to a differential receiver with
ground C
V.35 interface requires a T or delta network termination at
the receiver end and the generator end. The receiver
differential impedance measured at the connector must be
100
nals (A
In V.35 mode, both switches S1 and S2 inside the LTC2846
are on, connecting the T network impedance as shown in
Figure 19. The 30k input 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 as
shown in Figure 20.
14
GENERATOR
50
50
'
10 , and the impedance between shorted termi-
and B
'
, inputs A
LTC2846
V.35 DRIVER
125
Figure 18. Typical V.35 Interface
'
) and ground C
A
B
C
Figure 20. V.35 Driver
'
U
connected to A, B
INTERCONNECTING
BALANCED
CABLE
INFORMATION
U
124
'
must be 150
C
B
A
'
'
'
W
TERMINATION
S2
'
connected to B. The
125
CABLE
S1
51.5
51.5
15 . For the
LOAD
50
50
U
15 .
2844 F20
RECEIVER
A
B
C
2844 F18
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 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 600 A.
LTC2846 Supplies
The LTC2846 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 and
C3. The V
All capacitors are 16V and should be placed as close as
possible to the LTC2846 to reduce EMI.
The LTC2846 has an internal boost switching regulator
which generates a 5V output from the 3.3V supply as
shown in Figure 22. The 5V V
pump and transceivers as well as its companion chip.
5V
B
C
A
'
'
'
EE
C3
1 F
DD
Figure 19. V.35 Receiver Configuration
capacitor C4 should be a minimum of 3.3 F.
R1
51.5
R2
51.5
S1
and V
S2
C1
1 F
C5
10 F
Figure 21. Charge Pump
124
7
6
5
8
R3
EE
V
C1
C1
V
DD
CC
as shown in Figure 21. A voltage
+
–
GND
R8
6k
S3
LTC2846
EE
CC
20k
20k
R5
R4
. Three 1 F surface mounted
supplies its internal charge
DD
GND
C2
C2
V
EE
+
–
and a voltage inverter
R6
10k
R7
10k
33
32
31
30
RECEIVER
+
LTC2846
2844 F19
2844 F21
C2
1 F
C4
3.3 F
sn2844 2844fs