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PDF LTC2872 Data sheet ( Hoja de datos )
| Número de pieza | LTC2872 | |
| Descripción | RS232/RS485 Dual Multiprotocol Transceiver | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC2872
RS232/RS485 Dual
Multiprotocol Transceiver
with Integrated Termination
Features
n Four RS232 and Two RS485 Transceivers
n 3V to 5.5V Supply Voltage
n 20Mbps RS485 and 500kbps RS232
n Automatic Selection of Integrated RS485 (120Ω)
and RS232 (5kΩ) Termination Resistors
n Half-/Full-Duplex RS485 Switching
n Logic Loopback Mode
n High ESD: ±16kV on Line I/O
n 1.7V to 5.5V Logic Interface
n Supports Up to 256 RS485 Nodes
n RS485 Receiver Full Failsafe Eliminates UART Lockup
n Available in 38-Pin 5mm × 7mm QFN Package
Applications
n Flexible RS232/RS485/RS422 Interface
n Software Selectable Multiprotocol Interface Ports
n Point-of-Sale Terminals
n Cable Repeaters
n Protocol Translators
n PROFIBUS-DP Networks
Description
The LTC®2872 is a robust pin-configurable transceiver
that supports RS232, RS485, and RS422 standards while
operating on a single 3V to 5.5V supply. The LTC2872 can
be configured as four RS232 single-ended transceivers
or two RS485 differential transceivers, or combinations
of both, on shared I/O lines.
Pin-controlled integrated termination resistors allow
for easy interface reconfiguration, eliminating external
resistors and control relays. Half-duplex switches allow
four-wire and two-wire RS485 configurations. Loopback
mode steers the driver inputs to the receiver outputs for
diagnostic self-test. The RS485 receivers support up to
256 nodes per bus, and feature full failsafe operation for
floating, shorted or terminated inputs.
An integrated DC/DC boost converter uses a small induc-
tor and one capacitor, eliminating the need for multiple
supplies for driving RS232 levels.
www.DataSheet.co.kr
L, LT, LTC, LTM, Linear Technology, the Linear logo and µModule are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
Typical Applications
RS485 Mode with Duplex Control
1.7V TO VCC 470nF
3V TO 5.5V
22µH
2.2µF
RS485
FULL HALF
DUPLEX
VL CAP SW
H/F LTC2872
DY1
VCC
Y1
Z1
2.2µF
A1
RA1
B1
Y2
DY2
Z2
2.2µF
RA2
VDD
A2
B2
VEE
2.2µF
2.2µF
RS232 Mode
1.7V TO VCC 470nF
3V TO 5.5V
22µH
VL CAP SW
LTC2872
DY1
VCC
Y1
DZ1 Z1
RA1 A1
RB1 B1
DY2 Y2
Mixed Mode with RS485 Termination
1.7V TO VCC 470nF
3V TO 5.5V
22µH
2.2µF 2.2µF
RS485
OFF ON
TERMINATION
VL CAP SW
LTC2872
TE485-1
DY1
RA1
VCC
Y1
120Ω
Z1
A1
120Ω
B1
2.2µF
DY2 Y2
DZ2 Z2
RA2 A2
DZ2 Z2
RA2 A2
2.2µF
RB2
VDD
B2 RB2
VEE VDD
2.2µF 2.2µF
B2
VEE
2872 TA01
2.2µF
2872f
1
Datasheet pdf - http://www.DataSheet4U.net/
1 page  
LTC2872
S witching Characteristics The l denotes the specifications which apply over the full operating
temperature range,
noted. VL ≤ VCC.
otherwise
specifications
are
at
TA
=
25°C.
VCC
=
VL
=
3.3V,
TE485_1
=
TE485_2
=
0V,
LB
=
0V
unless
otherwise
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
RS485 AC Characteristics
Maximum Data Rate
(Note 3)
l 20
Mbps
tPLHD485
tPHLD485
tSKEWD485
tRD485, tFD485
ttZLLZDD448855,, ttZHHZDD448855,
tZHSD485, tZLSD485
tPLHR485, tPHLR485
Driver Propagation Delay
Driver Propagation Delay Difference
|tPLHD485 – tPHLD485|
Driver Skew (Y to Z)
Driver Rise or Fall Time
Driver Output Enable or Disable Time
Driver Enable from Shutdown
Receiver Input to Output
RDIFF = 54Ω, CL = 100pF (Figure 4)
RDIFF = 54Ω, CL = 100pF (Figure 4)
RDIFF = 54Ω, CL = 100pF (Figure 4)
RDIFF = 54Ω, CL = 100pF (Figure 4)
FEN = VL, RL = 500Ω, CL = 50pF (Figure 5)
FEN = 0V, RL = 500Ω, CL = 50pF (Figure 5)
C(NLo=te155)pF, VCM = 1.5V, |A–B| = 1.5V, (Figure 6)
l
l
l
l
l
l
l
20 70
16
1.5 ±8
7.6 15
120
0.2 2
55 85
ns
ns
ns
ns
ns
ms
ns
tSKEWR485
Differential Receiver Skew
|tPLHR485 – tPHLR485|
tRR485, tFR485
Receiver Output Rise or Fall Time
tZLR485, tZHR485
tLZR485, tHZR485
Receiver Output Enable or Disable Time
tRTEN485, tRTZ485
Termination Enable or Disable Time
RS232 AC Characteristics
CL = 15pF (Figure 6)
CL = 15pF (Figure 6)
FEN = VL, RL = 1k, CL = 15pF (Figure 7)
FEN = VL, VB = 0V, VAB = 2V (Figure 8) (Note 5)
l
l
l
l
19
3 15
30 85
100
ns
ns
ns
µs
Maximum Data Rate
Driver Slew Rate (Figure 9)
tPHLD232, tPLHD232 Driver Propagation Delay
tSKEWD232
Driver Skew
tZLD232, tZHD232
tLZD232, tHZD232
Driver Output Enable or Disable Time
tPHLR232, tPLHR232 Receiver Propagation Delay
tSKEWR232
Receiver Skew
tRR232, tFR232
Receiver Rise or Fall Time
tZLR232, tZHR232,
tLZR232, tHZR232
Receiver Output Enable or Disable Time
Power Supply Generator
RL = 3kΩ, CL = 2500pF,www.DataSheet.co.kr
RL = 3kΩ, CL = 500pF (Note 3)
RL = 3kΩ, CL = 2500pF
RL = 3kΩ, CL = 50pF
RL = 3kΩ, CL = 50pF (Figure 9)
RL = 3kΩ, CL = 50pF (Figure 9)
FEN = VL, RL = 3kΩ, CL = 50pF (Figure 10)
CL = 150pF (Figure 11)
CL = 150pF (Figure 11)
CL = 150pF (Figure 11)
FEN = VL, RL = 1kΩ, CL = 150pF (Figure 12)
l 100
l 500
l4
l
30
l 12
50
l 0.4 2
l 60 200
25
l 60 200
l 0.7 2
kbps
kbps
V/µs
V/µs
µs
ns
µs
ns
ns
ns
µs
VDD/VEE Supply Rise Time
FEN = , (Notes 3 and 4)
l
0.2 2
ms
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2. All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to device ground unless
otherwise specified.
Note 3. Guaranteed by other measured parameters and not tested directly.
Note 4. Time from FEN until VDD ≥ 5V and VEE ≤ –5V. External
components as shown in typical application.
Note 5. Condition applies to A, B for H/F = 0V, and Y, Z for H/F = VL.
Note 6. This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions.
Overtemperature protection activates at a junction temperature exceeding
150°C. Continuous operation above the specified maximum operating
junction temperature may result in device degradation or failure.
Note 7. Guaranteed by design and not subject to production test.
2872f
5
Datasheet pdf - http://www.DataSheet4U.net/
5 Page 
Test Circuits
GND
OR
DY
VL
DRIVER
Y
+
V–OD
Z
RL
RL
+
V–OC
2872 F01
Figure 1. RS485 Driver DC Characteristics
LTC2872
Y OR Z
GND
OR
DY
DRIVER
VL
Z OR Y
IOZD485, IOSD485
+– VOUT
2872 F02
Figure 2. RS485 Driver Output Short-Circuit Current
IIN485
+– VIN
A OR B
RECEIVER
B OR A
RIN485 =
VIN
IIN485
www.DataSheet.co.kr
2872 F03
Figure 3. RS485 Receiver Input Current and Resistance (Note 5)
Y
DY DRIVER
Z
RDIFF
CL
CL
DY tPLHD485
Y, Z VOD
tSKEWD485
½VOD
Y-Z
90%
10%
0V
tRD485
Figure 4. RS485 Driver Timing Measurement
tPLHD485
VL
0V
90%
0V 10%
tFD485
2872 F04
2872f
11
Datasheet pdf - http://www.DataSheet4U.net/
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LTC2872.PDF ] | |
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