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FEATURES
Integrated, Logic-Selectable 120Ω Termination
Resistor
3.3V Supply Voltage
20Mbps Maximum Data Rate
No Damage or Latchup Up to ±25kV HBM
High Input Impedance Supports 256 Nodes
www.Da(Cta,SIh-eGerta4Ud.ec)om
Operation Up to 125°C (H-Grade)
Guaranteed Failsafe Receiver Operation Over the
Entire Common Mode Range
Current Limited Drivers and Thermal Shutdown
Delayed Micropower Shutdown: 5μA Maximum
(C, I-Grade)
Power Up/Down Glitch-Free Driver Outputs
Low Operating Current: 370μA Typical in
Receive Mode
Compatible with TIA/EIA-485-A Specifications
Available in 10-Pin 3mm × 3mm DFN, 12-Pin
4mm × 3mm DFN and 16-Pin SSOP Packages
APPLICATIONS
Low Power RS485/RS422 Transceiver
Level Translator
Backplane Transceiver
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
LTC2854/LTC2855
3.3V 20Mbps RS485/RS422
Transceivers with Integrated
Switchable Termination
DESCRIPTION
The LTC®2854 and LTC2855 are low power, 20Mbps
RS485/RS422 transceivers operating on 3.3V supplies.
The receiver includes a logic-selectable 120Ω termina-
tion, one-eighth unit load supporting up to 256 nodes per
bus (C, I-Grade), and a failsafe feature that guarantees a
high output state under conditions of floating or shorted
inputs.
The driver maintains a high output impedance over the
entire common mode range when disabled or when the
supply is removed. Excessive power dissipation caused by
bus contention or a fault is prevented by current limiting
all outputs and by a thermal shutdown.
Enhanced ESD protection allows the LTC2854 to withstand
±25kV (human body model) and the LTC2855 to withstand
±15kV on the transceiver interface pins without latchup
or damage.
PRODUCT SELECTION GUIDE
PART NUMBER
LTC2854
LTC2855
DUPLEX
HALF
FULL
PACKAGE
DFN-10
SSOP-16, DFN-12
TYPICAL APPLICATION
RO R
RE
TE
DE
DI D
LTC2854
120Ω
LTC2854
120Ω
120Ω
LTC2854
R RO
RE
TE
DE
D DI
285455 TA01
LTC2854 at 20Mbps into 54Ω
DI
2V/DIV
A
B
A-B
R
D
RO RE TE DE DI
20ns/DIV
285455 TA01b
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LTC2854/LTC2855
ABSOLUTE MAXIMUM RATINGS (Note 1)
Supply Voltage (VCC) ................................... –0.3V to 7V
Logic Input Voltages (RE, DE, DI, TE)............ –0.3V to 7V
Interface I/O:
A, B, Y, Z ...................................... (VCC –15V) to +15V
(A-B) or (B-A) with Terminator Enabled ..................6V
Receiver Output Voltage (RO) ........ –0.3V to (VCC +0.3V)
Operating Temperature (Note 4)
LTC2854C, LTC2855C .............................. 0°C to 70°C
LTC2854I, LTC2855I ............................ –40°C to 85°C
LTC2854H, LTC2855H........................ –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
GN Package ...................................................... 300°C
PIN CONFIGURATION
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TOP VIEW
RO 1
10 VCC
RE 2
9B
DE 3 11 8 A
DI 4
7 NC
TE 5
6 GND
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
EXPOSED PAD (PIN 11) PCB GND CONNECTION
TJMAX = 125°C, θJA = 43°C/W
θJC = 2.96°C/W
TOP VIEW
RO 1
RE 2
12 VCC
11 A
DE 3 13 10 B
DI 4
9Z
TE 5
8Y
GND 6
7 NC
DE PACKAGE
12-LEAD (4mm × 3mm) PLASTIC DFN
EXPOSED PAD (PIN 13) PCB GND CONNECTION
TJMAX = 125°C, θJA = 44°C/W
θJC = 4.3°C/W
TOP VIEW
RO 1
RE 2
DE 3
DI 4
TE 5
GND 6
NC 7
NC 8
16 VCC
15 A
14 B
13 Z
12 Y
11 NC
10 NC
9 NC
GN PACKAGE
16-LEAD (NARROW 0.150) PLASTIC SSOP
TJMAX = 125°C, θJA = 110°C/W
θJC = 40°C/W
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2854CDD#PBF
LTC2854CDD#TRPBF LCQG
10-Lead (3mm × 3mm) Plastic DFN
0°C to 70°C
LTC2854IDD#PBF
LTC2854IDD#TRPBF
LCQG
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 85°C
LTC2854HDD#PBF
LTC2854HDD#TRPBF LCQG
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 125°C
LTC2855CDE#PBF
LTC2855CDE#TRPBF 2855
12-Lead (4mm × 3mm) Plastic DFN
0°C to 70°C
LTC2855IDE#PBF
LTC2855IDE#TRPBF
2855
12-Lead (4mm × 3mm) Plastic DFN
–40°C to 85°C
LTC2855HDE#PBF
LTC2855HDE#TRPBF 2855
12-Lead (4mm × 3mm) Plastic DFN
–40°C to 125°C
LTC2855CGN#PBF
LTC2855CGN#TRPBF 2855
16-Lead (Narrow 0.150) Plastic SSOP 0°C to 70°C
LTC2855IGN#PBF
LTC2855IGN#TRPBF
2855I
16-Lead (Narrow 0.150) Plastic SSOP –40°C to 85°C
LTC2855HGN#PBF
LTC2855HGN#TRPBF 2855H
16-Lead (Narrow 0.150) Plastic SSOP –40°C to 125°C
LEAD BASED FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2854CDD
LTC2854CDD#TR
LCQG
10-Lead (3mm × 3mm) Plastic DFN
0°C to 70°C
LTC2854IDD
LTC2854IDD#TR
LCQG
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 85°C
LTC2854HDD
LTC2854HDD#TR
LCQG
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 125°C
LTC2855CDE
LTC2855CDE#TR
2855
12-Lead (4mm × 3mm) Plastic DFN
0°C to 70°C
LTC2855IDE
LTC2855IDE#TR
2855
12-Lead (4mm × 3mm) Plastic DFN
–40°C to 85°C
LTC2855HDE
LTC2855HDE#TR
2855
12-Lead (4mm × 3mm) Plastic DFN
–40°C to 125°C
LTC2855CGN
LTC2855CGN#TR
2855
16-Lead (Narrow 0.150) Plastic SSOP 0°C to 70°C
LTC2855IGN
LTC2855IGN#TR
2855I
16-Lead (Narrow 0.150) Plastic SSOP –40°C to 85°C
LTC2855HGN
LTC2855HGN#TR
2855H
16-Lead (Narrow 0.150) Plastic SSOP –40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/
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LTC2854/LTC2855
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VCC = 3.3V unless otherwise noted (Note 2).
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Driver
|VOD|
Δ|VOD|
Differential Driver Output Voltage
Change in Magnitude of Driver
Differential Output Voltage for
Complementary Output States
R = , VCC = 3V (Figure 1)
R = 27Ω, VCC = 3V (Figure 1)
R = 50Ω, VCC = 3.13V (Figure 1)
R = 27Ω or R = 50Ω (Figure 1)
1.5
2
VCC V
VCC V
VCC V
0.2 V
VOC Driver Common Mode Output Voltage
Δ|VOC|
Change in Magnitude of Driver
Common Mode Output Voltage for
www.DataSheet4UC.ocmopmlementary Output States
IOZD Driver Three-State (High Impedance)
Output Current on Y and Z
R = 27Ω or R = 50Ω (Figure 1)
R = 27Ω or R = 50Ω (Figure 1)
DE = OV, (Y or Z) = –7V, 12V (LTC2855)
3V
0.2 V
±10 μA
IOSD Maximum Driver Short-Circuit Current –7V ≤ (Y or Z) ≤ 12V (Figure 2)
180 ±250
–250
300
mA
mA
Receiver
IIN
Receiver Input Current (A, B)
DE = TE = 0V, VCC = 0V or 3.3V, VIN = 12V
(Figure 3) (C, I-Grade)
DE = TE = 0V, VCC = 0V or 3.3V, VIN = –7V,
–100
(Figure 3) (C, I-Grade)
125 μA
μA
RIN Receiver Input Resistance
DE = TE = 0V, VCC = 0V or 3.3V, VIN = 12V
(Figure 3) (H-Grade)
DE = TE = 0V, VCC = 0V or 3.3V, VIN = –7V,
(Figure 3) (H-Grade)
RE = VCC or 0V, DE = TE = 0V,
VIN = –7V, –3V, 3V, 7V, 12V (Figure 3)
(C, I-Grade)
–145
96
125
250
μA
μA
kΩ
RE = VCC or 0V, DE = TE = 0V,
VIN = –7V, –3V, 3V, 7V, 12V (Figure 3)
(H-Grade)
48
125
kΩ
VTH Receiver Differential Input Threshold –7V ≤ B ≤ 12V
Voltage
±0.2 V
ΔVTH
VOH
VOL
IOZR
Receiver Input Hysteresis
Receiver Output HIGH Voltage
Receiver Output LOW Voltage
Receiver Three-State (High Impedance)
Output Current on RO
B = 0V
I(RO) = –4mA, A-B = 200mV, VCC = 3V
I(RO) = 4mA, A-B = –200mV, VCC = 3V
RE = VCC, 0V ≤ RO ≤ VCC
25
2.4
0.4
±1
mV
V
V
μA
IOSR
RTERM
Receiver Short-Circuit Current
Receiver Input Terminating Resistor
0V ≤ RO ≤ VCC
TE = VCC, VAB = 2V, VB = –7V, 0V, 10V
(Figure 8)
±85
108 120 156
mA
Ω
Logic
VIH
VIL
IINL
Supplies
Logic Input High Voltage
Logic Input Low Voltage
Logic Input Current
VCC = 3.6V
VCC = 3V
2
0.8
0 ±10
V
V
μA
ICCS
Supply Current in Shutdown Mode
DE = 0V, RE = VCC, TE = 0V
(LTC2854C/LTC2854I, LTC2855C/LTC2855I)
(LTC2854H, LTC2855H)
05
0 15
μA
μA
ICCR
Supply Current in Receive Mode
DE = 0V, RE = 0V, TE = 0V
370 900
μA
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LTC2854/LTC2855
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VCC = 3.3V, TE = 0V unless otherwise noted (Note 2).
SYMBOL PARAMETER
ICCT
ICCTR
Supply Current in Transmit Mode
Supply Current with Both Driver and
Receiver Enabled
ICCTERM
ICCTERMR
Supply Current in Termination Mode
Supply Current in Receive and
Termination Mode
ICCTERMT
Supply Current in Transmit and
Termination Mode
ICCTERMTR Supply Current with Driver, Receiver
and Termination Enabled
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ESD Protection
CONDITIONS
No Load, DE = VCC, RE = VCC, TE = 0V
No Load, DE = VCC, RE = 0V, TE = 0V
DE = 0V, RE = VCC, TE = VCC
DE = 0V, RE = 0V, TE = VCC
DE = VCC, RE = VCC, TE = VCC
DE = VCC, RE = 0V, TE = VCC
MIN TYP MAX UNITS
450 1000
μA
450 1000
μA
110 180
μA
450 950
μA
470 1000
μA
470 1000
μA
ESD Protection for RS485/RS422 Pins A, B on LTC2854, Human Body Model
Y, Z, A, B on LTC2855, Human Body Model
±25 kV
±15 kV
SWITCHING CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VCC = 3.3V, TE = 0V unless otherwise noted (Note 2).
SYMBOL
Driver
fMAX
tPLHD, tPHLD
ΔtPD
tSKEWD
tRD, tFD
tZLD, tZHD, tLZD,
tHZD
tZHSD, tZLSD
tSHDN
Receiver
tPLHR, tPHLR
tSKEWR
tRR, tFR
tZLR, tZHR, tLZR,
tHZR
tZHSR, tZLSR
tRTEN, tRTZ
PARAMETER
Maximum Data Rate
Driver Input to Output
Driver Input to Output Difference
|tPLHD-tPHLD|
Driver Output Y to Output Z
Driver Rise or Fall Time
Driver Enable or Disable Time
Driver Enable from Shutdown
Time to Shutdown
Receiver Input to Output
Differential Receiver Skew
|tPLHR-tPHLR|
Receiver Output Rise or Fall Time
Receiver Enable/Disable
Receiver Enable from Shutdown
Termination Enable or Disable Time
CONDITIONS
MIN TYP MAX UNITS
Note 3
RDIFF = 54Ω, CL = 100pF (Figure 4)
RDIFF = 54Ω, CL = 100pF (Figure 4)
RDIFF = 54Ω, CL = 100pF (Figure 4)
RDIFF = 54Ω, CL = 100pF (Figure 4)
RL = 500Ω, CL = 50pF, RE = 0 (Figure 5)
RL = 500Ω, CL = 50pF, RE = VCC (Figure 5)
(DE = , RE = VCC) or (DE = 0, RE )
(Figure 5)
20
Mbps
10 50
ns
16
ns
1 ±6
4 12.5
70
ns
ns
ns
8 μs
100 ns
CL = 15pF, VCM = 1.5V, |VAB| = 1.5V, tR and
tF < 4ns (Figure 6)
CL = 15pF (Figure 6)
CL = 15pF (Figure 6)
RL = 1k, CL =15pF, DE = VCC (Figure 7)
RL = 1k, CL = 15pF, DE = 0V (Figure 7)
VB = 0V, VAB = 2V, RE = VCC, DE = 0V
(Figure 8)
50 70
16
3 12.5
50
8
100
ns
ns
ns
ns
μs
μs
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: Maximum data rate is guaranteed by other measured parameters
and is not tested directly.
Note 4: 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.
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TEST CIRCUITS
GND
OR DI
VCC
DRIVER
Y
R
+
VOD
Z R+
V–OC
Figure 1. Driver DC Characteristics
LTC2854/LTC2855
GND
OR DI
VCC
DRIVER
Y
Z
IOSD
+
–7V to +12V
285455 F01-2
Figure 2. Driver Output Short-Circuit Current
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IIN
A OR B
VIN +–
RECEIVER
B OR A
285455 F03
RIN
=
VIN
IIN
Figure 3. Receiver Input Current and Input Resistance
Y
DI
DRIVER
Z
RDIFF
CL
CL
285455 F04a
VCC
DI
0V
Y, Z VO
tPLHD
1/2 VO
tSKEWD
tPHLD
90% 90%
Y-Z 10% 0 0 10%
285455 F04b
tRD tFD
Figure 4. Driver Timing Measurement
Y
VCC DI
OR DRIVER
GND
DE
Z
RL
CL
GND
OR
VCC
RL
CL
VCC
OR
GND
285455 F05a
VCC
DE
0V
VCC
Y OR Z
VOL
VOH
Z OR Y
0V
1/2 VCC
VO
tZLD,
tZLSD
1/2 VCC
1/2 VCC
tZHD,
tZHSD
tLZD
0.5V
0.5V
tHZD,
tSHDN
285455 F05b
Figure 5. Driver Enable and Disable Timing Measurements
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