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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.
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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
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LTC2872
Absolute Maximum Ratings
(Note 1)
Input Supplies
VCC, VL...................................................... –0.3V to 7V
Generated Supplies
VDD................................................. VCC – 0.3V to 7.5V
VEE.......................................................... 0.3V to –7.5V
VDD – VEE...............................................................15V
SW............................................ –0.3V to (VDD + 0.3V)
CAP.............................................. 0.3V to (VEE – 0.3V)
A1, A2, B1, B2, Y1, Y2, Z1, Z2.......................–15V to 15V
DY1, DY2, DZ1, DZ2, RXEN1, RXEN2, DXEN1, DXEN2,
LB, H/F, TE485_1, TE485_2,
485/232_1, 485/232_2................................. –0.3V to 7V
FEN, RA1, RA2, RB1, RB2................–0.3V to (VL + 0.3V)
Differential Enabled Terminator Voltage
(A1-B1 or A2-B2 or Y1-Z1 or Y2-Z2)......................±6V
Operating Temperature
LTC2872C................................................. 0°C to 70°C
LTC2872I..............................................–40°C to 85°C
Storage Temperature Range................... –65°C to 125°C
Pin Configuration
TOP VIEW
VCC 1
A1 2
B1 3
Y1 4
GND 5
Z1 6
DY1 7
DZ1 8
RXEN1 9
DXEN1 10
TE485_1 11
TE485_2 12
38 37 36 35 34 33 32
39
VEE
13 14 15 16 17 18 19
31 VCC
30 A2
29 B2
28 Y2
27 GND
26 Z2
25 DY2
24 DZ2
23 RXEN2
22 DXEN2
21 VCC
20 VDD
UHF PACKAGE
38-LEAD (5mm × 7mm) PLASTIC QFN
TJMAX = 125°C, θJA = 34.7°C/W
EXPOSED PAD (PIN #39) IS VEE, MUST BE SOLDERED TO PCB
www.DataSheet.co.kr
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2872CUHF#PBF
LTC2872CUHF#TRPBF 2872
38-Lead (5mm × 7mm) Plastic QFN
0°C to 70°C
LTC2872IUHF#PBF
LTC2872IUHF#TRPBF 2872
38-Lead (5mm × 7mm) Plastic QFN
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
2
2872f
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LTC2872
E lectrical Characteristics The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = VL = 3.3V, TE485_1 = TE485_2 = 0V, LB = 0V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Power Supply
VCC Supply Voltage Operating Range
VL Logic Supply Voltage Operating Range
VCC Supply Current in Shutdown Mode
VL ≤ VCC
RXEN1
DXEN1
=
=
RXEN2
DXEN2
=
=
FVELN,
=
H/F
=
0V
l3
l 1.7
l
5.5
VCC
8 60
V
V
µA
V(OCuCtSpuutpspUlynClouardreendt)
in RS485
(Note 3)
Transceiver
Mode
V(OCuCtSpuutpspUlynClouardreendt)
in RS232
(Note 3)
Transceiver
Mode
485/232_1 = 485/232_2 = DXEN1 =
DXEN2 = VL, RXEN1 = RXEN2 = 0V
D48X5E/N2132=_D2 X=ERNX2E=NV1L=;
485/232_1 =
RXEN2 = 0V
l
l
4.5 7
5.5 8
mA
mA
VMLoSduep(pOluytCpuutrsreUnnt lionaRdeSd4)85 or RS232 Transceive DXEN1 = DXEN2 = VL, RXEN1 = RXEN2 = 0V l
05
µA
RS485 Drivers
|VOD|
∆|VOD|
VOC
∆|VOC|
Differential Output Voltage
Difference in Magnitude of Differential Output
Voltage for Complementary Output States
Common Mode Output Voltage
Difference in Magnitude of Common Mode
Output Voltage for Complementary Output States
RRLL
=
=
∞27,ΩV,CVCC=C
3V (Figure 1)
= 4.5V (Figure
1)
RL = 27Ω, VCC = 3V (Figure 1)
RL = 50Ω, VCC = 3.13V (Figure 1)
RL = 27Ω, VCC = 3V (Figure 1)
RL = 50Ω, VCC = 3.13V (Figure 1)
RL = 27Ω or 50Ω (Figure 1)
RL = 27Ω or 50Ω (Figure 1)
l
l 2.1
l 1.5
l2
l
l
l
l
6V
VCC V
VCC V
VCC V
0.2 V
0.2 V
3V
0.2 V
IOZD485 Three-State (High Impedance) Output Current
IOSD485 Maximum Short-Circuit Current
RS485 Receiver
VOUT = 12V or –7V,
V = 0V or 3.3V (Figure 2)CC
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–7V ≤ VOUT ≤ 12V (Figure 2)
l –100
l –250
125 µA
250 mA
IIN485
Input Current
V(FIiNgu=r1e23V) o(Nr o–t7eV5, )VCC = 0V or 3.3V
l –100
125 µA
RIN485
Input Resistance
VIN = 12V or –7V, VCC = 0V or 3.3V
(Figure 3) (Note 5)
125 kΩ
Differential Input Signal Threshold Voltage (A–B) –7V ≤ (A or B) ≤ 12 (Note 5)
l
±200 mV
Differential Input Signal Hysteresis
B = 0V (Notes 3, 5)
190 mV
Differential Input DC Failsafe Threshold Voltage –7V ≤ (A or B) ≤ 12 (Note 5)
(A–B)
l –200 –65
0
mV
Differential Input DC Failsafe Hysteresis
B = 0V (Note 5)
30 mV
VOL
VOH
RTERM
Output Low Voltage
Output High Voltage
Three-State (High Impedance) Output Current
Short-Circuit Output Current
Terminating Resistor
Output Low, I(RA) = 3mA (Sinking),
3V ≤ VL ≤ 5.5V
Output Low, I(RA) = 1mA (Sinking),
1.7V ≤ VL < 3V
Output High, I(RA) = –3mA (Sourcing),
3V ≤ VL ≤ 5.5V
Output High, I(RA) = –1mA (Sourcing),
1.7V ≤ VL < 3V
0V ≤ RA ≤ VL, VL = 5.5V
0V ≤ RA ≤ VL, VL = 5.5V
TE485 = VL, A–B = 2V, B = –7V, 0V, 10V
(Figure 8) (Note 5)
l
l
l VL – 0.4
l VL – 0.4
l
l
l 108
0
120
0.4
0.4
±5
±135
156
V
V
V
V
μA
mA
Ω
2872f
3
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LTC2872
E lectrical Characteristics The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = VL = 3.3V, TE485_1 = TE485_2 = 0V, LB = 0V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
RS232 Driver
VOLD
VOHD
Output Low Voltage
Output High Voltage
Three-State (High Impedance) Output Current
RL = 3kΩ, VEE ≤ –6V
RL = 3kΩ, VDD ≥ 6.5V
Y or Z = ±15V
l –5
l5
l
–5.7 VEE
6.2 VDD
±156
V
V
µA
Output Short-Circuit Current
Y or Z = 0V
l
±35 ±90
mA
RS232 Receiver
Input Threshold Voltage
l 0.6 1.5 2.5
V
Input Hysteresis
l 0.1 0.4 1.0
V
Output Low Voltage
Output High Voltage
Input Resistance
I(RA, RB) = 1mA (Sinking),
1.7V ≤ VL ≤ 5.5V
I(RA, RB) = –1mA (Sourcing),
1.7V ≤ VL ≤ 5.5V
–15V ≤ (A, B) ≤ 15V, Receiver Enabled
l 0.4 V
l VL – 0.4
V
l 3 5 7 kΩ
Three-State (High Impedance) Output Current
Output Short-Circuit Current
Logic Inputs
0V ≤ (RA, RB) ≤ VL
VL = 5.5V, 0V ≤ (RA, RB) ≤ VL
l
0 ±5
μA
l
±25 ±50
mA
Threshold Voltage
Input Current
l 0.4
l
0.75• VL
0 ±5
V
µA
Power Supply Generator
VDD Regulated VDD Output Voltage
VEE Regulated VEE Output Voltage
RS232 Drivers Enabled, Outputs Loaded with
R = 3kΩ to GND, DY1 = DY2 = V ,L
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L
DZ1 = DZ2 = 0V (Note 3)
7V
–6.3 V
ESD
Interface Pins (A, B, Y, Z)
Human Body Model to GND
or Unpowered (Note 7)
or
VCC,
Powered
±16 kV
All Other Pins
Human Body Model (Note 7)
±4 kV
4
2872f
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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
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