LINER LTC2855 ±60v rugged profibus rs485 transceiver Datasheet

LTC2876/LTC2877
±60V Rugged PROFIBUS
RS485 Transceivers
Features
Description
PROFIBUS IEC 61158-2 Compliant
nn Protected from Overvoltage Line Faults to ±60V
nn ±52kV ESD Interface Pins, ±15kV All Other Pins
nn ±2kV (Level 4) IEC61000-4-4 Fast Transient Burst
nn ±25V Working Common Mode Range
nn 20Mbps Maximum Baud Rate
nn 1.65V to 5.5V Logic Supply Pin for Flexible Digital
Interfacing (LTC2877)
nn 5V Supply Can Operate Down to 3V for Low Power,
Low Swing Applications
nn Fully Balanced Differential Receiver Thresholds with
240mV Hysteresis for Superior Noise Tolerance and
Low Duty Cycle Distortion
nn Receiver Failsafe for Open, Shorted and Terminated
Conditions
nn Wide Operating Temperature Range: –40°C to 125°C
nn Available in Small DFN and MSOP Packages
The LTC®2876 and LTC2877 are PROFIBUS RS485
transceivers designed to meet the test specifications for
PROFIBUS-DP masters and PROFIBUS-DP slaves, fully
compatible with IEC 61158-2, type 3: medium attachment
unit (MAU). With operation up to 20Mbps, the LTC2876/
LTC2877 supports all PROFIBUS data rates up to 12Mbps.
nn
The LTC2876 and LTC2877 are exceptionally robust, tolerating ±60V faults on the bus pins and protected to ±52kV
ESD. These devices are suitable for harsh environments
or where 24V power might be inadvertently connected.
Extended ±25V input common mode range and full failsafe operation improve data communication reliability in
noisy systems.
The LTC2876 and LTC2877 meet PROFIBUS and RS485
specifications with a supply voltage of 4.5V to 5.5V but
can operate down to 3V with reduced supply current.
Product Selection Guide
Applications
PROFIBUS-DP
Industrial Communication Networks
nn RS485 and RS422 Systems
nn 3V Low Voltage Differential Signaling
nn
PART NUMBER
LOGIC SUPPLY PIN
PACKAGE
LTC2876
NO
DFN-8, MSOP-8
LTC2877
YES
DFN-10, MSOP-10
nn
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Typical Application
1.8V
0.1µF
VL
5V
LTC2877
VCC
5V
1µF
390Ω
RO
PB
µC
SENSOR
PB
RE
PROFIBUS
CABLE
220Ω
PA
ZO = 150Ω
390Ω
DE
390Ω
B´
PB–PA
2V/DIV
NEAR END
220Ω
PA
DI
Eye Diagram of 12Mbps Signal at
the Near and Far End of a 100m
PROFIBUS Cable Driven by the
LTC2877 Using 28 –1 PRBS Pattern
A´
390Ω
B´– A´
2V/DIV
FAR END
GND
28767 TA01a
20ns/DIV
28767 TA01b
28767fa
For more information www.linear.com/LTC2876
1
LTC2876/LTC2877
Absolute Maximum Ratings
(Notes 1, 2)
Supply Voltages (VCC, VL)............................. –0.3V to 6V
Logic Input Voltages (RE, DE, DI)................. –0.3V to 6V
Line Interface I/O (PA, PB)........................... –60V to 60V
Line Interface I/O Difference (PB–PA)...... –120V to 120V
Receiver Output (RO)
LTC2876.......................................–0.3V to VCC + 0.3V
LTC2877........................................ –0.3V to VL + 0.3V
Operating Ambient Temperature Range (Note 3)
LTC287xC................................................. 0°C to 70°C
LTC287xI..............................................–40°C to 85°C
LTC287xH........................................... –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10sec).................... 300°C
Pin Configuration
LTC2876
LTC2876
TOP VIEW
RO
1
RE
2
DE
3
DI
4
TOP VIEW
8 VCC
9
GND
RO
RE
DE
DI
7 PA
6 PB
5 GND
1
2
3
4
9
GND
8
7
6
5
VCC
PA
PB
GND
MS8E PACKAGE
8-LEAD PLASTIC MSOP
DD PACKAGE
8-LEAD (3mm × 3mm) PLASTIC DFN
TJMAX = 150°C, θJA = 40°C/W, θJC = 10°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
TJMAX = 150°C, θJA = 43°C/W, θJC = 5.5°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
LTC2877
LTC2877
TOP VIEW
RO
1
RE
2
DE
3
DI
4
VL
5
TOP VIEW
10 VCC
11
GND
RO
RE
DE
DI
VL
9 PA
8 PB
7 NC
6 GND
11
GND
10
9
8
7
6
VCC
PA
PB
NC
GND
MSE PACKAGE
10-LEAD PLASTIC MSOP
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
TJMAX = 150°C, θJA = 43°C/W, θJC = 5.5°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
2
1
2
3
4
5
TJMAX = 150°C, θJA = 40°C/W, θJC = 10°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
28767fa
For more information www.linear.com/LTC2876
LTC2876/LTC2877
Order Information
http://www.linear.com/product/LTC2876#orderinfo
Lead Free Finish
TUBE
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2876CMS8E#PBF
LTC2876IMS8E#PBF
LTC2876HMS8E#PBF
LTC2876CMS8E#TRPBF
LTC2876IMS8E#TRPBF
LTC2876HMS8E#TRPBF
LTGTN
LTGTN
LTGTN
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
LTC2876CDD#PBF
LTC2876IDD#PBF
LTC2876HDD#PBF
LTC2876CDD#TRPBF
LTC2876IDD#TRPBF
LTC2876HDD#TRPBF
LGTM
LGTM
LGTM
8-Lead Plastic DFN
8-Lead Plastic DFN
8-Lead Plastic DFN
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
LTC2877CMSE#PBF
LTC2877IMSE#PBF
LTC2877HMSE#PBF
LTC2877CMSE#TRPBF
LTC2877IMSE#TRPBF
LTC2877HMSE#TRPBF
LTGTQ
LTGTQ
LTGTQ
10-Lead Plastic MSOP
10-Lead Plastic MSOP
10-Lead Plastic MSOP
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
LTC2877CDD#PBF
LTC2877IDD#PBF
LTC2877HDD#PBF
LTC2877CDD#TRPBF
LTC2877IDD#TRPBF
LTC2877HDD#TRPBF
LGTP
LGTP
LGTP
10-Lead Plastic DFN
10-Lead Plastic DFN
10-Lead Plastic DFN
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on nonstandard 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/. Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = VL = 5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
Primary Power Supply
PROFIBUS, RS485
l
4.5
Low Voltage RS485 (Note 6)
l
3.0
1.65
TYP
MAX
UNITS
Supplies
VCC
5.5
V
V
VL
Logic Interface Power Supply
LTC2877 Only
l
VCC
V
ICCS
LTC2876 Supply Current in Shutdown
Mode
DE = 0V, RE = VCC, DI = VCC
l
0
5
µA
DE = 0V, RE = VCC, DI = 0V
l
12
25
µA
LTC2877 Supply Current in Shutdown
Mode
DE = 0V, RE = VL = VCC , DI = 0V or VL
l
0
5
µA
ICCR
Supply Current with Only Receiver
Enabled
No Load, DE = 0V, RE = 0V
l
600
900
µA
ICCD
Supply Current with Only Driver
Enabled
No Load, DE = RE = VCC = VL
l
700
1100
µA
ICCDR
Supply Current with Both Driver and
Receiver Enabled
No Load, DE = VCC = VL, RE = 0V
l
750
1200
µA
LTC2877 Logic Supply Current in
Shutdown Mode
DE = 0V, RE = VL, DI = VL
l
0
5
µA
DE = 0V, RE = VL, DI = 0V
l
12
25
µA
DE = VL, RE = 0V, DI = VL
l
30
60
µA
DE = VL, RE = 0V, DI = 0V
l
65
120
µA
LTC2877 Logic Supply Current with
Both Driver and Receiver Enabled
28767fa
For more information www.linear.com/LTC2876
3
LTC2876/LTC2877
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = VL = 5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Driver
VOD(PP)
Differential Bus Output Voltage (B´–A´) PROFIBUS LOAD (Figure 1)
with PROFIBUS Load
RCABLE = 0Ω, VCC = 4.5V to 5.5V
RCABLE = 5.5Ω, VCC = 4.5V to 5.5V
RCABLE = 11Ω, VCC = 4.75V to 5.5V
l
l
l
VBPP-APP
Single-Ended Bus Output Amplitude
Difference (B´PP – A´PP)
All of the Conditions Above
l
VBPP+APP
Single-Ended Bus Output Amplitude
Sum |B´PP + A´PP|
All of the Conditions Above
l
|VOD(485)|
RS485 Differential Driver Output
Voltage, in Either Logic State
Figure 2 with No Load
l
|VOD(422)|
RS422 Differential Driver Output
Voltage, Either Logic State
4
4
4
7
7
7
0.5
4
VP-P(DIFF)
VP-P(DIFF)
VP-P(DIFF)
V
V
VCC
V
RL = 27Ω,VCC = 4.5V to 5.5V (Figure 2)
l
1.5
3.4
V
RL = 27Ω,VCC = 3.0V to 3.6V (Figure 2)
l
0.8
1.8
V
Figure 2 with No Load
l
VCC
V
RL = 50Ω,VCC = 4.5V to 5.5V (Figure 2)
l
2
4
V
RL = 50Ω,VCC = 3.0V to 3.6V (Figure 2)
l
1
2
V
Δ|VOD(485)|, RS485, RS422 Change in Magnitude of RL = 27Ω (RS485) or
Δ|VOD(422)| Driver Differential Output Voltage
RL = 50Ω (RS422) (Figure 2)
l
0.2
V
VOC(485),
VOC(422)
RL = 27Ω (RS485) or
RL = 50Ω (RS422) (Figure 2)
l
3
V
Δ|VOC(485)|, RS485, RS422 Change in Magnitude of RL = 27Ω (RS485) or
Δ|VOC(422)| Driver Common-Mode Output Voltage RL = 50Ω (RS422) (Figure 2)
l
0.2
V
RS485, RS422 Driver Common-Mode
Output Voltage
Maximum Driver Short-Circuit Current
–60V ≤ (PB or PA) ≤ 60V (Figure 3)
l
IIN
Input Current (PA, PB)
VCC = 0V or 5V, VBUS = 12V (Figure 4)
VCC = 0V or 5V, VBUS = –7V (Figure 4)
l
l
–100
RIN
Input Resistance
VBUS = –25V or 25V (Figure 4)
l
75
VCM
Common Mode Input Voltage
(PA+PB)/2 for Data Reception
VTS+
Differential Input Signal Threshold
Voltage (PB–PA) Rising
–25V ≤ VCM ≤ 25V, Edge Rates > 100mV/µs
(Note 5) (Figure 13)
l
50
VTS–
Differential Input Signal Threshold
Voltage (PB–PA) Falling
–25V ≤ VCM ≤ 25V, Edge Rates > 100mV/µs
(Note 5) (Figure 13)
l
–50
IOSD
±150
±250
mA
160
µA
µA
Receiver
112
135
kΩ
±25
V
120
200
mV
–120
–200
mV
l
ΔVTS
Differential Input Signal Hysteresis
Edge Rates > 100mV/µs (Note 5) (Figure 13)
VTFS+
Differential Input Failsafe Threshold
Voltage (PB–PA) Rising
–25V ≤ VCM ≤ 25V, DC Bus Voltages
(Figure 13)
l
–20
–75
–200
mV
VTFS–
Differential Input Failsafe Threshold
Voltage (PB–PA) Falling
–25V ≤ VCM ≤ 25V, DC Bus Voltages
(Figure 13)
l
–50
–120
–200
mV
ΔVTFS
Differential Input Failsafe Hysteresis
DC Bus Voltages (Figure 13)
VOH
Receiver Output High Voltage
VCC ≥ 4.5V, I(RO) = –3mA (LTC2876)
VL ≥ 2.25V, I(RO) = –3mA (LTC2877)
VL < 2.25V, I(RO) = –2mA (LTC2877)
l
l
l
VOL
Receiver Output Low Voltage
VL ≥ 1.65V, I(RO) = 3mA (LTC2877)
VCC ≥ 3.0V, I(RO) = 3mA (LTC2876)
l
l
4
240
mV
45
mV
VCC – 0.4V
VL – 0.4V
VL – 0.4V
V
V
V
0.4
0.4
V
V
Receiver Three-State (High Impedance) RE = High, RO = 0V
Output Current on RO
l
–20
–40
µA
Receiver Three-State (High Impedance) RE = High, RO = VCC (LTC2876) or VL
Output Current on RO
(LTC2877)
l
0
5
µA
28767fa
For more information www.linear.com/LTC2876
LTC2876/LTC2877
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = VL = 5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
Receiver Short-Circuit Current
RE = Low, RO = 0V or VCC (LTC2876) or VL
(LTC2877)
l
MIN
Low Level Input Voltage (DE, DI, RE)
LTC2876, 3.0 ≤ VCC ≤ 5.5V
l
LTC2877, 1.65 ≤ VL ≤ 5.5V
l
LTC2876, 3.0 ≤ VCC ≤ 5.5V
l
0.75 • VCC
0.75 • VL
TYP
MAX
UNITS
±12
±20
mA
Logic
High Level Input Voltage (DE, DI, RE)
LTC2877, 1.65 ≤ VL ≤ 5.5V
l
Logic Input Current Low (DE)
DE = 0V
l
Logic Input Current Low (DI, RE)
DI or RE = 0V
l
0.25 • VCC
V
0.25 • VL
V
V
V
0
–5
µA
–3
–10
–20
µA
3
10
20
µA
0
5
µA
Logic Input Current High (DE)
DE = VCC (LTC2876) or VL (LTC2877)
l
Logic Input Current High (DI, RE)
(DI, RE) = VCC (LTC2876) or VL (LTC2877)
l
ESD Protection Level of Interface Pins
(PA, PB)
Human Body Model to GND or VCC, or VL ,
Powered or Unpowered
Human Body Model to GND, Unpowered
±52
kV
ESD Protection Level of All Other Pins
(DE, DI, RE, VCC, VL)
Human Body Model
±15
kV
ESD (Note 4)
±26
kV
Switching Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = VL = 5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
fMAX
Maximum Data Rate
(Note 4)
l
MIN
TYP
MAX
tPLHD, tPHLD
Driver Input to Output
VCC = 3.3V or 5V (Figure 5)
l
13
50
ns
ΔtPD
Driver Input to Output Difference
|tPLHD – tPHLD|
(Figure 5)
l
2
9
ns
tSKEWD
Driver Output PB to Output PA
(Figure 5)
l
±9
ns
tRD, tFD
Driver Rise or Fall Time
VCC = 3.3V or 5V (Figure 5)
l
tZLD, tZHD,
tLZD, tHZD
Driver Enable or Disable Time
RE = 0V (Figure 6)
l
tZHSD, tZLSD
Driver Enable from Shutdown
RE = High (Figure 6)
l
15
µs
tSHDND
Time to Shutdown with DE
RE = High (Figure 6)
l
180
ns
tPLHR, tPHLR
Receiver Input to Output
VCM = 2.25V, (PB–PA) = ±1.5V,
tR and tF < 4ns, VCC = 3.3V or 5V (Figure 7)
l
50
70
ns
ΔtPR
Receiver Input to Output Difference
|tPLHR – tPHLR|
(Figure 7)
l
2
14
ns
tRR, tFR
Receiver Output Rise or Fall Time
(Figure 7)
l
3
15
ns
tZLR, tZHR,
tLZR, tHZR
Receiver Enable/Disable Time
DE = High (Figure 8)
l
40
ns
tZHSR, tZLSR
Receiver Enable from Shutdown
DE = 0V, (Figure 9)
l
9
µs
tSHDNR
Time to Shutdown with RE
DE = 0V, (Figure 9)
l
40
ns
20
UNITS
Mbps
Driver
4
15
ns
180
ns
Receiver
28767fa
For more information www.linear.com/LTC2876
5
LTC2876/LTC2877
Electrical Characteristics
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: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature exceeds 150°C when overtemperature protection is active.
Continuous operation above the specified maximum operating temperature
may result in device degradation or failure.
6
Note 4: Not tested in production.
Note 5: The dependency on edge rate is tested indirectly.
Note 6: Does not meet RS485 or PROFIBUS specifications. See the
Applications Information section for more information about running with
a 3V supply.
28767fa
For more information www.linear.com/LTC2876
LTC2876/LTC2877
Typical Performance Characteristics
TA = 25°C. VCC = VL = 5V, unless otherwise noted. (Note 2)
5
750
ICCDR
ICCD
ICCS (nA)
2
600
ICCR
550
3
3.5
4
4.5
5
VCC SUPPLY VOLTAGE (V)
ICCS (nA)
0
5.5
575
28767 G01
7
3
Driver Output Low/High Voltage
vs Output Current
5
3
3.5
4
4.5
VCC (V)
5
0
–50 –25
5.5
OUTPUT CURRENT (mA)
4
20
30
40
OUTPUT CURRENT (mA)
80
28767 G07
25 50 75 100 125 150
TEMPERATURE (°C)
Driver and Receiver Propagation
Delay vs VCC
RECEIVER
50
OUTPUT LOW
40
0
–40
–80
–160
–60
0
28767 G06
60
OUTPUT HIGH
–120
50
20
28767 G05
120
VOL (VCC = 5.0V)
10
15
DATA RATE (Mbps)
1
160
VOH (VCC = 5.0V)
1
5
VOD(PP) PROFI LOAD (Fig. 1), VCC = 5V
VOD(422) (Fig. 2, RL = 50Ω), VCC = 5V
VOD(485) (Fig. 2, RL = 27Ω), VCC = 5V
VOD(422) (Fig. 2, RL = 50Ω), VCC = 3.3V
VOD(485) (Fig. 2, RL = 27Ω), VCC = 3.3V
3
Driver Output Short-Circuit
Current vs Voltage
VOL (VCC = 3.3V)
0
2
28767 G04
2
No Load, VCC = 3.3V
4
4
0
20
VOH (VCC = 3.3V)
No Load, VCC = 5V
10
5
1
10
RS485 54Ω/100pF Load (Fig. 5) VCC = 3.3V
20
6
VOD (V)
VOD (V)
VL SUPPLY CURRENT (mA)
0.5
0
30
Driver Differential Output Voltage
vs Temperature
2
3
PROFI 100m cable w/term (Fig.1) VCC = 5V
28767 G03
5
10
15
DATA RATE (Mbps)
40
0
VOD(PP) PROFIBUS LOADS (Fig. 1)
VOD(422) (Fig. 2, RL = 50Ω)
VOD(485) (Fig. 2, RL = 27Ω)
6
1.0
5
RS485 54Ω/100pF Load (Fig. 5) VCC = 5V
28767 G02
VL = 5V, CRO = 15pF
VL = 5V, CRO = 0pF
VL = 1.65V, CRO = 15pF
VL = 1.65V, CRO = 0pF
0
50
Driver Differential Output Voltage
vs Supply Voltage
1.5
DRIVER OUTPUT VOLTAGE (V)
1
0.1
0
25 50 75 100 125 150
TEMPERATURE (°C)
500
–50 –25
2.0
0
10
ICCR
3.0
0
100
ICCD
650
VL Supply Current vs Data Rate
2.5
1k
ICCDR
PROPAGATION DELAY (ns)
500
1
725
ICCS (nA)
3
650
ICCDR, ICCD, ICCR (µA)
4
700
VCC Supply Current vs Data Rate
10k
800
ICCS (nA)
VCC SUPPLY CURRENT (µA)
VCC Supply Current vs Temperature
for Various Modes, No Load
VCC SUPPLY CURRENT (mA)
VCC Supply Current vs Voltage for
Various Modes, No Load
–40
–20
0
20
OUTPUT VOLTAGE (V)
40
40
30
20
DRIVER
10
60
28767 G08
0
3
3.5
4
4.5
VCC
5
5.5
28767 G09
28767fa
For more information www.linear.com/LTC2876
7
LTC2876/LTC2877
Typical Performance Characteristics
TA = 25°C. VCC = VL = 5V, unless otherwise noted. (Note 2)
Driver Output Skew
vs Temperature
Driver Output Propagation Delay
Difference vs Temperature
30
5
5
27
4
4
24
3
21
2
15
VCC = 5V
12
3
2
VCC = 5V
1
∆tPD (ns)
VCC = 3.3V
18
tSKEWD (ns)
PROPAGATION DELAY (ns)
Driver Propagation Delay
vs Temperature
0
–1
VCC = 3.3V
1
–1
9
–2
6
–3
–3
3
–4
–4
0
–50 –25
–5
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
0
28767 G10
VCC = 5V
0
VCC = 3.3V
–2
–5
–50 –25
25 50 75 100 125 150
TEMPERATURE (°C)
28767 G12
Receiver Propagation Delay
Difference vs Temperature
Receiver Output Voltage
vs Output Current (Source and Sink)
5
60
6
VL = 5.5V
RECEIVER OUTPUT VOLTAGE (V)
3
55
2
∆tPR (ns)
PROPAGATION DELAY (ns)
4
50
VCC = 3.3V
VCC = 3.3V
1
0
VCC = 5V
–1
–2
45
–3
–4
40
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
25 50 75 100 125 150
TEMPERATURE (°C)
28767 G11
Receiver Propagation Delay
vs Temperature
VCC = 5V
0
–5
–50 –25
5
4
VL = 3.3V
3
VL = 2.25V
2
VL = 1.65V
1
VL = 1.65V TO 5.5V
0
25 50 75 100 125 150
TEMPERATURE (°C)
0
28767 G14
28767 G13
0
4
6
8
2
OUTPUT CURRENT (ABSOLUTE VALUE, mA)
28767 G15
Receiver Output Voltage
vs VL Voltage (LTC2877)
PROFIBUS Operation at 12Mbps
VCC = 5V
RS485 Operation at 20Mbps
VCC = 3.3V
400
VOL
VL–VOH
VOL
VL–VOH
VOL OR VOH (mV)
300
for I(RO) = +2mA
for I(RO) = –2mA
for I(RO) = +3mA
for I(RO) = –3mA
DI
2V/DIV
DI
5V/DIV
PB
1V/DIV
200
PB
0.5V/DIV
PA
1V/DIV
DOUBLE PROFIBUS TERMINATION
RCABLE = 0Ω (Fig. 1)
100
50ns/DIV
0
1.5
8
PA
0.5V/DIV
2.5
3.5
VL (V)
4.5
RLDIFF = 54Ω; CL=100pF (Fig. 5)
28767 G17
20ns/DIV
28767 G18
5.5
28767 G16
28767fa
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LTC2876/LTC2877
Pin Functions
(LTC2876/LTC2877)
RO (Pin 1): Receiver Output. Supplied by VCC in the
LTC2876 or VL in the LTC2877. If the receiver is enabled
(RE low) and PB–PA > 200mV, then RO will be high. If
PB–PA < –200mV, then RO will be low. If the receiver inputs
are open, shorted, or terminated without being driven for
more than about 1.5µs, RO will be high. Integrated 250k
pull-up resistor to supply.
RE (Pin 2): Receiver Enable. Logic levels defined by the VCC
supply in the LTC2876 or the VL supply in the LTC2877.
A low input enables the receiver. A high input forces the
receiver output into a high impedance state. If RE is high
with DE low, the device enters a low power shutdown state.
Integrated 500k pull-up resistor to supply.
DE (Pin 3): Driver Enable. Logic levels defined by the VCC
supply in the LTC2876 or the VL supply in the LTC2877.
A high input on DE enables the driver. A low input forces
the driver outputs into a high impedance state. If DE is
low with RE high, the device enters a low power shutdown
state. Integrated 500k pull-down resistor to ground.
DI (Pin 4): Driver Input. Logic levels defined by the VCC
supply in the LTC2876 or the VL supply in the LTC2877.
If the driver outputs are enabled (DE high), then a low on
DI drives a negative differential voltage between PB and
PA. A high on DI, with the driver outputs enabled, drives a
positive differential voltage between PB and PA. Integrated
500k pull-up resistor to supply.
VL (NA/Pin 5): Logic supply: 1.65V ≤ VL ≤ VCC. Powers
RO, RE, DE, and DI on LTC2877 only. Bypass with 0.1µF
ceramic capacitor to GND.
GND (Pin 5, 9/Pin 6,11): Ground
NC (NA/Pin 7): Not Internally Connected.
PB (Pin 6/Pin 8): PROFIBUS B. Non-inverting receiver
input and non-inverting driver output. Connect this to
the B wire (positive) in a PROFIBUS network. In most
non-PROFIBUS applications, this should connect to the
A terminal. See the Applications Information section for
more information on A vs B naming conventions.
PA (Pin 7/Pin 9): PROFIBUS A. Inverting receiver input
and inverting driver output. Connect this to the A wire
(negative) in a PROFIBUS network. In most non-PROFIBUS
applications, this should connect to the B terminal. See
the Applications Information section for more information
on A vs B naming conventions.
VCC (Pin 8/Pin 10): Power Supply. 4.5V ≤ VCC ≤ 5.5V for
PROFIBUS and RS485 compliant applications; 3.0V ≤ VCC
≤ 5.5V for a wide range of usage. See 3.3V Operation in
the Applications Information section for details. Bypass
with 1µF ceramic capacitor to GND.
Exposed Pad (Pin 9/Pin 11): Must be connected to GND.
28767fa
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9
LTC2876/LTC2877
Block Diagram
3V TO 5.5V
LTC2876
VCC
VCC
VCC
RO
RECEIVER
RE
PB
MODE
CONTROL
PA
DE
VCC
DI
DRIVER
GND
28767 BD1
3V TO 5.5V
1.65V TO VCC
LTC2877
VCC
VL
VCC
RO
RECEIVER
RE
PB
MODE
CONTROL
PA
DE
VCC
DI
DRIVER
GND
28767 BD2
10
28767fa
For more information www.linear.com/LTC2876
LTC2876/LTC2877
Test Circuits
VCC
VCC
LTC2876/LTC2877
B´PP
VCC
A´PP
B´
RO
HIGH
HIGH
390Ω
PB
RE
DE
220Ω
PA
DI
390Ω
RCABLE
B´
VOD(PP)
A´
390Ω
+
–
B´– A´
0
220Ω
RCABLE
A´
0
VBPP–APP = |B´PP – A´PP|
VBPP+APP = B´PP + A´PP
390Ω
MEASUREMENTS TAKEN AT STEADY STATE
28767 F01
Figure 1. Driver Differential Output Voltages for PROFIBUS Load
VOD(485)+
VOD(485)–
VCC
∆|VOC(485)|
PB
LTC2876/LTC2877
CM
PA
RO
HIGH
HIGH
RE
PB
RL
VOD(485)
DE
PA
CM
PB–PA
0
RL
DI
VOD(485) = PB–PA
VOC(485)
+
–
∆|VOD(485)| = |VOD(485)+ – VOD(485)– |
FOR RS422 MEASUREMENTS, SUBSTITUTE 485 WITH 422 IN THIS FIGURE.
MEASUREMENTS TAKEN AT STEADY STATE
28767 F02
Figure 2. Driver Output Voltages in RS485 and RS422 Configurations
VCC
LTC2876/LTC2877
RO
HIGH
HIGH
HIGH OR LOW
RE
DE
PB
PA
DI
IOSD
+
–
–60V TO +60V
28767 F03
Figure 3. Drive Output Short-Circuit Current
28767fa
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11
LTC2876/LTC2877
Test Circuits
VCC
LTC2876/LTC2877
RO
HIGH OR LOW
LOW
LOW
RE
PB
DE
IIN
PA
+
–
DI
RIN =
VBUS
VBUS
IIN
28767 F04
Figure 4. Receiver Input Current and Input Resistance
VCC
VCC*
LTC2876/LTC2877
tPLHD
DI
RO
tSKEWD
PA
HIGH
HIGH
RE
PB
DE
100pF
54Ω
PA
DI
tPHLD
0V
100pF
VO
½VO
PB
90%
PB–PA
10%
0
0
tRD
90%
10%
tFD
*FOR THE LTC2877, SUBSTITUTE VL FOR VCC
28767 F05
Figure 5. Driver Timing Measurement
12
28767fa
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LTC2876/LTC2877
Test Circuits
VCC
VCC*
DE
LTC2876/LTC2877
RO
500Ω
PB
RE
LOW OR
HIGH
50pF
VCC WHEN
DI LOW
GND WHEN
DI HIGH
VCC
PA OR PB
DE
500Ω
PA
DI
LOW OR
HIGH
½VCC*
0V
50pF
tZLD,
tZLSD
tLZD
½VCC
VOL
0.5V
VOH
GND WHEN
DI LOW
VCC WHEN
DI HIGH
PB OR PA
0.5V
½VCC
0V
tZHD,
tZHSD
tHZD,
tSHDND
*FOR THE LTC2877, SUBSTITUTE VL FOR VCC
28767 F06
Figure 6. Driver Enable, Disable and Shutdown Timing Measurements
VCC
∆tPR = |tPLHR – tPHLR|
LTC2876/LTC2877
1.5V
RO
15pF
LOW
LOW
LOW
PB–PA
PB
RE
DE
PA
VCM
±(PB–PA)/2
0V
–1.5V
±(PB–PA)/2
tPLHR
VCC*
90%
½VCC*
10%
RO
0
tPHLR
½VCC*
tRR
DI
90%
10%
tFR
*FOR THE LTC2877, SUBSTITUTE VL FOR VCC
28767 F07
Figure 7. Receiver Propagation Delay Measurements
28767fa
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13
LTC2876/LTC2877
Test Circuits
VCC FOR DI LOW
GND FOR DI HIGH
VCC
1k
VCC*
tZLR
RE
LTC2876/LTC2877
15pF
RO
RE
LOW OR
HIGH
tLZR
VCC
RO
HIGH
½VCC*
0V
PB
DE
½VCC*
VOL
0.5V
VOH
PA
RO
DI
0.5V
½VCC*
0V
tZHR
tHZR
*FOR THE LTC2877, SUBSTITUTE VL FOR VCC
28767 F08
Figure 8. Receiver Enable and Disable Timing Measurements
VCC FOR CASE1
GND FOR CASE2
VCC
1k
VCC*
LTC2876/LTC2877
15pF
LOW
DE
DI
tSHDNR
VCC*
CASE 1 CASE 2
LOW
½VCC*
0V
RO
RE
tZLSR
RE
PB
PA
0V
VCC
VCC
0V
RO
½VCC*
VOL
0.5V
VOH
RO
0.5V
½VCC*
0V
tZHSR
*FOR THE LTC2877, SUBSTITUTE VL FOR VCC
tSHDNR
28767 F09
Figure 9. Receiver Shutdown Timing Measurements
14
28767fa
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LTC2876/LTC2877
Applications Information
Note: Specifications in this section represent typical values
unless otherwise noted.
be compliant to PROFIBUS requirements. The LTC2876/
LTC2877 was designed specifically to meet PROFIBUS and
RS485 requirements and is tested in a way that ensures this.
PROFIBUS-DP and RS485
Cable and Termination Differences from RS485
PROFIBUS-DP can communicate over a variety of media,
including copper wires, fiber optics, and even air in an
infrared communicator. By far, the most commonly used
media is a twisted pair of wires connecting devices that
communicate with TIA/EIA-485-A (RS485) transceivers.
The cable and termination network used for PROFIBUS is
different than for RS485 as illustrated in Figure 10. The
PROFIBUS network includes bus biasing resistors that
are used in conjunction with the differential termination
resistors on each end of the bus. The cable is a shielded
twisted pair with an impedance of 150Ω. Oddly enough,
the effective differential resistance of the specified termination network is 172Ω, which is not a perfect match for the
150Ω cable, resulting in a slightly underdamped network.
This manifests itself as a small bump, or increase in the
signal voltage, at the receiving end of the cable, lasting
twice as long as the cable propagation delay.
RS485 offers high speed differential signaling that is
robust for communication between multiple devices over
long distances in noisy environments such as factory
applications.
Not All RS485 Transceivers Are Suitable for PROFIBUS
Although the PROFIBUS standard specifies the use of
RS485 devices at the physical layer, there are differences
in the cable, termination, and driver requirements from
RS485. A device meeting RS485 specifications may not
5V
PROFIBUS
MASTER
In contrast, the RS485 network shows the preferred
configuration with only differential termination resistors
at each end of the bus, matching the 120Ω characteristic
impedance of the cable.
Profibus Multi-Node Network
Twisted Pair Cable (ZO = 150Ω)
5V
390Ω
390Ω
220Ω
220Ω
390Ω
PROFIBUS
STATION
390Ω
PROFIBUS
STATION
PROFIBUS
STATION
RS485 Multi-Node Network
Twisted Pair Cable (ZO = 120Ω)
RS485
MASTER
120Ω
120Ω
RS485
NODE
RS485
NODE
RS485
NODE
28767 F10
Figure 10. Cable and Termination Differences in RS485 and PROFIBUS Multi-Node Networks.
PROFIBUS Type A Cable and Termination Shown in PROFIBUS Example (Top)
28767fa
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15
LTC2876/LTC2877
Applications Information
Driver Output Requirement Differences from RS485
Driver Operation
The driver requirements for PROFIBUS are specified differently than how the RS485 standard specifies them. A
key difference is the terminated driver output voltage, VOD,
as described below.
The driver is enabled when the LTC2876/LTC2877 is
powered up, DE is high, and there are no thermal faults.
The polarity of PB–PA follows that of DI. That is, when DI
is high, PB drives to a voltage that is greater than PA. If DI
is low, PA is higher than PB. When the driver is disabled
with DE low, both outputs are high impedance and the
overall pin resistance is dominated by the receiver inputs
sharing pins PA and PB.
The PROFIBUS driver output levels are required to meet
the following condition as stated in the “Test Specification
for PROFIBUS DP Masters” and “Test Specification for
PROFIBUS DP Slaves”:
• The differential voltage between A- and B-line shall be
a minimum of 4V and a maximum of 7V, peak-to-peak
differential.
• This measurement shall be taken at the far end of the
cable in use, with termination at each end.
On the other hand, RS485 specifies the following:
• The differential voltage between A- and B-line shall be
a minimum of 1.5V and a maximum of 5V, peak differential.
• This measurement shall be taken at the driver terminals
with a 54Ω resistor between A and B.
Clearly, these requirements are quite different. A common
misunderstanding is that if an RS485 driver develops more
than 2.1V across a 54Ω RS485 resistive load, then it will
meet PROFIBUS requirements when used with a PROFIBUS termination network. This is not always the case.
Furthermore, the strength of the driver can be too high,
exceeding the upper limit of the PROFIBUS Specification
(7VP-P). The best way to ensure PROFIBUS compliance
is to test the device with a PROFIBUS load.
The LTC2876 and LTC2877 are tested with a PROFIBUS load
and with extra resistance added to represent cable losses
for 100m and 200m to ensure they meet the PROFIBUS
VOD requirement. The devices are also fully tested with
RS485 loads to ensure they meet RS485 specifications.
See the Electrical Characteristics section for details.
16
Driver Overvoltage and Overcurrent
Protection
The driver outputs PA and PB are protected from short
circuits to any voltage within the absolute maximum range
of –60V to +60V, with a maximum differential voltage
of –120V to +120V. The maximum short-circuit current
to any voltage within this range is ±250mA. The driver
includes a progressive foldback current limiting circuit
that continuously reduces the driver current limit with
increasing output short circuit voltage to better manage
power dissipation and heating effects.
The LTC2876/LTC2877 also features thermal shutdown
protection that disables the driver and receiver in case of
excessive power dissipation (see Note 3).
Receiver
The receiver provides full PROFIBUS and RS485 compatibility. When enabled, the state of RO reflects the polarity
of (PB–PA). When the receiver is disabled, the output is
high impedance and RO weakly pulled high through an
internal 250k pull-up resistor.
High Receiver Input Resistance Permits 200 Nodes
The RS485 and PROFIBUS specifications allows for up to
32 receivers, each contributing one unit load, to be connected together in one network. The input resistance of
the LTC2876/LTC2877 is guaranteed to be at least 6.25
times higher, and drawing proportionally less current,
than a standard RS485 load, permitting a total of 200
receivers per contiguous network. The input load of the
receiver is unaffected by enabling/disabling the receiver
or by powering/depowering the device.
28767fa
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LTC2876/LTC2877
Applications Information
Balanced Signal Threshold
LTC2876, LTC2877 - BALANCED THRESHOLDS
The LTC2876/LTC2877 differential threshold is 120mV
for rising input signals and –120mV for falling signals.
This constitutes 240mV of hysteresis, which offers a high
rejection to signal noise that can otherwise falsely trip
a receiver. Since these thresholds are centered around
zero volts (i.e. “balanced”), the duty cycle is preserved
for small amplitude signals with slewed edges—typical
of what is observed at the end of a long cable. Figure 11
illustrates this point.
In contrast to this, some RS485 receivers have an unbalanced receiver threshold, used to address failsafe
conditions (more on this below). That is, the rising and
falling differential signal thresholds are both negative.
Figure 12 illustrates an example where the rising threshold
is –75mV and falling threshold is –120mV. This has two
disadvantages. First, the hysteresis is only 45mV in this
example, reducing the tolerance to noise, compared to the
240mV of hysteresis in the LTC2876/LTC2877. Secondly,
these unbalanced thresholds cause a duty cycle or pulse
width distortion at the receiver output relative to the input
signal. Figure 12 illustrates how a competitor part, using
the negative thresholds in this example introduces a duty
cycle distortion that becomes increasingly worse with low
input signal levels and slow input edge rates.
Failsafe Operation
The LTC2876 and LTC2877 have a failsafe feature that
guarantees the receiver output will be in a logic 1 state
(the idle state) when the inputs are shorted, left open, or
terminated but not driven for more than about 1.5µs. This
failsafe feature is guaranteed to work for inputs spanning
the entire common mode range of –25V to +25V.
Many RS485 receivers simply employ a negative threshold
(for rising and falling signals) to achieve failsafe operation.
If the inputs are shorted together (0V differential), the
receiver produces a high output, consistent with failsafe.
However, this asymmetrical threshold comes with the
disadvantages of pulse width distortion and sensitivity to
signal noise as described in the section above.
The LTC2876/LTC2877 achieves full failsafe operation,
while reaping the benefits of a balanced receiver threshold.
+200mV
+120mV
(PB–PA)
VTS+
0
–120mV
VTS–
–200mV
RO
28767 F11
Figure 11. The LTC2876/LTC2877 Balanced Signal Threshold
Voltages Preserve the Duty Cycle of an Incoming Signal. The
Differential Signal Received (Top) Has a Duty Cycle of 50%,
and Is Reflected In the Receiver Output, RO (Bottom)
UNBALANCED THRESHOLDS
+200mV
(PB–PA)
0
–75mV
–120mV
VTS+
VTS–
–200mV
RO
28767 F12
Figure 12. Typical Competitor Unbalanced Signal Threshold
Voltages Distort the Duty Cycle of an Incoming Signal. Input Is
50% Duty Cycle (Top) But the Receiver Output Is Not 50% Duty
Cycle (Bottom)
Failsafe operation is performed with a window comparator to determine when the differential input voltage falls
between the rising and falling signal thresholds (VTS+,
and VTS–). If this condition persists for more than about
1.5µs then the receiver switches over to using the failsafe
thresholds (VTFS–, VTFS+), as illustrated in Figure 13 and
Figure 14. The delay allows normal data signals to transition
through the threshold region without being interpreted as
a failsafe condition, and thus maintaining the benefits of a
balanced threshold receiver. However, for fault conditions
(e.g., shorted, open, or undriven lines) that persist for
more than 1.5µs, the failsafe thresholds are engaged and
the receiver output drives high, indicating this condition.
The failsafe delay also prevents unwanted receiver output
28767fa
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17
LTC2876/LTC2877
Applications Information
or RE goes low during this delay, the delay timer is reset
and the chip does not enter shutdown. This reduces the
chance of accidentally entering shutdown if DE and RE are
driven in parallel by a slowly changing signal or if DE and
RE are driven by two independent signals with a timing
skew between them.
∆VTS
∆VTFS
RO
(PB–PA)
VTS – , VTFS –
–200mV
–120mV
VTFS +
VTS +
–75mV
0
+120mV
+200mV
28767 F13
Figure 13. The LTC2876/LTC2877 Signal Thresholds (VTS–, VTS+)
and Failsafe Thresholds (VTFS–, VTFS+)
+200mV
+120mV
VTS+
(PB–PA) 0
–75mV
–120mV
VTFS+
VTS–, VTFS–
–200mV
2
1
RO
3
4
28767 F14
Figure 14. LTC2876/LTC2877 Receiver Operation. Event 1: Signal
Rises into Region Between Signal Thresholds, Resulting in the
RO Transitioning to a Failsafe Condition After a Fixed Delay of
About 1.5µs. Event 2: Input Signal Falls Below Negative Signal
Threshold, Resulting in an Immediate Fall on RO. Event 3:
Signal Glitches into the Region Between Signal Thresholds for a
Period Less Than the Failsafe Delay Time (~1.5µs), Resulting in
an Unchanged Output. Event 4: Signal Transitions Above Rising
Signal Threshold, Resulting in an Immediate Rise in RO
glitches resulting from receiver inputs that momentarily
cross into the region between the signal rising and falling
thresholds as illustrated in Figure 14, event 3.
Shutdown Mode Delay
The LTC2876 and LTC2877 feature a low power shutdown
mode that is entered when both the driver and receiver
are simultaneously disabled (pin DE low and RE high).
A shutdown mode delay of approximately 250ns (not
tested in production) is imposed after the state is received
before the chip enters shutdown. If either DE goes high
18
This shutdown mode delay does not affect the outputs of
the transmitter and receiver, which start to switch to the
high impedance state upon the reception of their respective
disable signals as defined by the parameters tSHDND and
tSHDNR. The shutdown mode delay affects only the time
when all the internal circuits that draw DC power from
VCC are turned off.
Power-Up/Down Glitch-Free Outputs
The LTC2876 and LTC2877 employ an undervoltage detection circuit to control the activation of the on-chip circuitry.
During power-up, PB, PA, and RO are undriven, until the
VCC supply reaches a voltage sufficient to reliably operate
the chip. In this mode, only the internal pull-up resistor
on RO and the receiver input resistance to ground on PA
and PB offer weak conduction paths at those pins. As the
supply voltage rises above the undervoltage threshold, and
if the device is configured for drive mode, the PB and PA
pins become active and are driven to a state that reflects
the input condition on DI. Likewise, if the device is configured for receive mode, the RO pin is driven high or low to
reflect the state of the differential voltage across PB–PA.
During power down, the reverse occurs; the supply undervoltage detection circuit senses low supply voltage
and immediately puts the chip into shutdown. The driver
and receiver outputs go to the undriven state. RO is pulled
up through the internal 250k pull-up resistor and PA, PB
are pulled low through the 125k receiver input resistors.
If the LTC2876/LTC2877 is powered or depowered when
configured for shutdown (RE = 0V and DE = VL (LTC2877)
or VCC (LTC2876) then RO, PB, and PA will remain in the
undriven state, without glitching high or low during the
supply transition. This allows the powering and depowering of the LTC2876/LTC2877 when connected onto a live
network without disturbing the lines.
28767fa
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LTC2876/LTC2877
Applications Information
±60V Fault Protection
technology. The naturally high breakdown voltage of this
technology provides protection in powered off and high
impedance conditions. Figure 15 further illustrates how
the driver and receiver inputs tolerate large voltages above
the supply and below ground without excessive device
currents. As shown, the driver outputs are reverse-diode
protected from voltages back-driven above VCC or below
ground. The receiver inputs use resistive dividers that
tolerate large positive and negative voltages. The LTC2876/
LTC2877 is protected from ±60V bus faults even with the
loss of GND or VCC.
TIA/EIA-485-A specifies that ground shifts between two
devices on a network can be as large as –7V to +12V
during operation. Most RS485 transceivers cannot safely
tolerate voltages on their interface pins that are much
higher than this range. However, industrial installations
may encounter voltages much greater than this, causing
damage to the devices.
This requirement means that a driver and receiver sharing
communication on a network must be able to operate with
a signal common mode voltage difference of –7V to 12V.
Competing PROFIBUS transceivers can be damaged by
pin voltages exceeding these levels by only a few volts.
The limited overvoltage tolerance makes implementation
of effective external protection networks difficult without
interfering with proper data network performance. Replacing standard RS485 transceivers with the LTC2876 or
LTC2877 can eliminate field failures due to overvoltage
faults without using costly external protection devices.
The ±60V fault protection of the LTC2876/LTC2877 is
achieved by using a high voltage BiCMOS integrated circuit
±25V Extended Common Mode Range
The LTC2876/LTC2877 receiver features an extended common mode range of –25V to +25V. The wide common mode
increases the reliability of operation in environments with
high common mode voltages created by electrical noise
or local ground potential differences due to ground loops.
This extended common mode range allows the LTC2876/
LTC2877 to transmit and receive under conditions that
would cause data errors or possible device damage in
competing products.
PB PA
LTC2876/LTC2877
SIMPLIFIED DRIVER
OUTPUT STAGE
VCC
VCC
LTC2876/LTC2877
SIMPLIFIED RECEIVER
INPUT STAGE
20:1
DIVIDE
TO RO
OUTPUT CIRCUITS
FROM DI
INPUT CIRCUITS
20:1
DIVIDE
28767 F15
Figure 15. Internal Circuit Structure at PA/PB Pins That Tolerates Large Positive and Negative Voltages
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19
LTC2876/LTC2877
Applications Information
Electrical Overstress Protection
Equipment used in industrial environments is often exposed to extremely high levels of electrical overstress
due to phenomena such as electrostatic discharges (ESD)
from personnel or equipment, electrical fast transients
(EFT) from switching high current inductive loads, and
even lightning surges. The LTC2876/LTC2877 has been
designed to thrive in these adverse conditions.
ESD
Perhaps the most common exposure to electrical overstress is ESD, which results from the build-up of electrical
charge on one object, and discharged onto another in
close proximity. The LTC2876/LTC2877 features exceptionally robust ESD protection. The bus interface pins
(PB and PA) are protected to ±52kV human body model
(HBM) with respect to GND when unpowered and ±26kV
with respect to GND, VCC, or VL when powered, without
latchup or damage, in any mode of operation. Every other
pin on the device is protected to ±15kV ESD (HBM) for
all-around robustness. Figure 16 shows an unprotected
LTC2876 struck repeatedly with 26kV from an ESD gun
using air discharge to illustrate the strike energy. The
device continues to function normally after the strikes,
without damage or cycling the power.
Figure 16. This Single Exposure Image Captures the Striking Robustness of an Unprotected LTC2876 Hit Repeatedly with 26kV ESD
Discharges While Operating without Damage or Circuit Latchup
20
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LTC2876/LTC2877
Applications Information
The IEC standard for ESD, IEC 61000-4-2, specifies a very
fast (sub-nanosecond) edge transient stimulus intended
for system level ESD testing and not specified at the device
level. However, if it is applied directly to the bus interface
pins, without any external protection devices, the LTC2876/
LTC2877 is protected to 4kV IEC when used in a typical application, powered or unpowered, and terminated with the
standard PROFIBUS load. This is not tested in production.
EFT
Electrical fast transients can result from arcing contacts
in switches and relays, common when switching inductive loads. The IEC standard for EFT is IEC61000-4-4 and
specifies a repetitive burst pattern lasting 60 seconds. The
LTC2876/LTC2877 is robust to EFT events and passes the
highest level recognized in the IEC standard: level 4, ±2kV
on the PA and PB pins, without any external protection.
Auxiliary Protection for Surge
Surge events represent the most severe transient conditions caused by such things as load switching in power
distribution systems, high current short circuit faults,
and lighting strikes. These are addressed in standard IEC
61000-4-5, which specifies repetitive voltage and current
waveforms used to deliver high power stimulus lasting tens
of microseconds each. The LTC2876/LTC2877 is designed
for high robustness against ESD and EFT, but the on-chip
protection is not able to absorb the energy associated with
the IEC 61000-4-5 surge transients. External protection is
necessary to achieve a high level of surge protection, and
can also extend the ESD and EFT protection to extremely
high levels.
In addition to providing transient protection, externally connected devices must preserve the ability of the LTC2876/
LTC2877 to operate over a wide common mode voltage
and yet safely clamp the pin voltage low enough to avoid
damage during the overstress event. The added protection
must be low in capacitance to avoid excessively loading
the transceiver bus, allowing operation at full data rate.
The LTC2876/LTC2877’s ±60V pin rating makes it easy
to find protection devices meeting these requirements.
Figure 21 shows a solution providing ±4kV protection of
the bus Interface pins (PA and PB) for all three IEC 61000
standards as follows:
IEC 61000-4-5 2nd Ed. 2005-11 Surge Level 4: ±4kV
(line to GND, 8/20µs waveform, each line coupled to
generator through 80Ω resistor per Figure 14 of the
standard)
IEC 61000-4-4 2nd Ed. 2004-07 EFT Level 4: ±4kV
(line to GND, 5kHz repetition rate, 15ms burst duration
every 300ms, 60s test duration, discharge coupled to
bus pins through 100pF capacitor per paragraph 7.3.2
of the standard)
IEC 61000-4-2 2nd Ed. 2008-12 ESD Level 3: ±4kV
contact (line to GND, direct discharge to bus pins with
transceiver and standard PROFIBUS resistor load and
protection circuit mounted on a ground referenced test
card per Figure 4 of the standard)
The TVS devices in Figure 21 have a typical clamp voltage
of about 36V, comfortably beyond the LTC2876/LTC2877’s
common mode operating range of ±25V and well below
the ±60V rating. Since the LTC2876/LTC2877 bus pins are
rated for ±60V, the clamping device must maintain voltages less than this when conducting peak current during
the overstress event. This relatively wide voltage window
permits the use of smaller, more resistive clamps, which
generally also have less capacitance.
Two of these TVS devices are used in an antiparallel configuration because each can only protect in one polarity.
The benefit of these uni-directional TVS devices is their low
capacitance, offering a total load of only about 50pF to the
signal lines in this configuration, permitting the LTC2876/
LTC2877 to communicate at maximum data rates with no
significant performance degradation.
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21
LTC2876/LTC2877
Applications Information
Bus Pins PA & PB Naming Convention
Table 1. PROFIBUS Type-A Cable Properties
PROFIBUS communicates with RS485 signaling through a
differential signal interface. These wires are labeled A and
B. The PROFIBUS standard specifies that the bus wire B
takes on a positive value with respect to bus wire A when
no station is transmitting data (during the idle periods).
However, the polarity convention of most RS485 devices
uses the opposite convention. That is, with no transmission on the bus, the receiver reports a logic value that
would result if A were higher than B—in this case a high
on RO. From a practical standpoint, this means that if a
general RS485 transceiver is connected to a PROFIBUS
network, the transceiver’s A pin must connect to the B
wire and the B pin connect to the A wire. Certainly this
can be confusing!
PROPERTY
VALUE
Impedance
135Ω to 165Ω
Capacitance
< 30pF/m
Loop Resistance
< 110Ω/km
Conductor Area
≥ 0.34mm2
Color of Sheath (Non-IS)
Violet
Color of Inner Conductor A
Green
Color of Inner Conductor B
Red
Since the LTC2876/LTC2877 was designed specifically
for PROFIBUS applications, the pin naming convention
was made to match the PROFIBUS specification. To avoid
confusion with other RS485 transceivers, the prefix “P”
was added, meaning “PROFIBUS.” If driver and receiver
are enabled, a high level on DI, will drive the bus lines so
that PB is higher than PA and the receiver will report a
high level on RO.
In PROFIBUS installations, connect PB to the B wire (red)
and PA to the A wire (green). For non-PROFIBUS RS485
applications, the PB pin should be connected to the A signal
and PA pin should be connect to the B signal to match the
convention of most other RS485 devices.
PROFIBUS Cables
It is recommended that PROFIBUS installations use cable
designed for PROFIBUS applications. Typically, Type A
cable and termination is used. This is a shielded twisted
pair with the following properties:
22
The three resistors that make up the termination network
should be placed at both ends of the bus and must be
powered during operation. If there are multiple nodes
communicating on the bus, only the nodes at the ends
should be terminated.
The cable shield helps to improve electromagnetic compatibility (EMC). It is recommended to ground both ends
of the shield, through the case of the connector, to the
chassis of the connected station. In applications where
ground potential differences exist between stations, for
example long distance transmission between buildings,
the shield should be grounded only at one end of the cable.
If the potential difference exceeds several volts, galvanic
isolation is recommended at one or more of the connected stations. In this case, consider using the LTM®2892
µModule isolator (see 3500VRMS Isolated PROFIBUS Node
with Termination on the last page).
If the shield cannot be grounded through the connector
case, pin 1 of the D-sub connector can be used as an
alternative, although the added inductance makes this
sub-optimal. In such a case, it is better to bare the cable
shield at an appropriate point and ground it with a short
cable or clamp to the metallic structure of the station.
Unshielded cable can be used in PROFIBUS installations
if there is no severe electromagnetic interference (EMI).
Do not use cables that are untwisted pairs.
28767fa
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LTC2876/LTC2877
Applications Information
Maximum PROFIBUS Cable Length
The following table gives the maximum cable segment
lengths at PROFIBUS baud rates, as specified in IEC
61158-2:
Table 2. PROFIBUS Maximum Cable Length
BAUD RATE (kbits/s)
MAX. SEGMENT LENGTH (m)
The D-sub connector is specified for use up to 12Mbps.
Inductors are often built into the cable connectors to
reduce unwanted ringing and reflections at data rates
above 1.5Mbits/s. Cable connectors are also available with
termination resistors that can be switched in/out.
Table 3. Pin Designation For D-Sub and M12 Connectors.
(Connections in Bold are Mandatory)
9.6
1200
19.2
1200
45.45
1200
93.75
1200
187.5
1000
500
400
1500
200
3000
100
5
3
GND for Bus Termination
6000
100
6
1
VCC (+5V) for Bus Termination
12000
100
7
PIN NUMBER
9-PIN D-Sub
M12
CONNECTION
1, Case
Thread
Cable Shield
2
3
GND for 24V Supply
4
4
8
CNTR-P
(Repeater Direction Control)
+24V Supply
2
9
Connectors
2
4
3
4
1
3
5
5
M12 PLUG
2
6
2
3
7
4
8
Not Used
Operation in RS485 and RS422 Systems
The LTC2876 and LTC2877 are completely compatible
with standard RS485 and RS422 networks. In these installations, the PB pin should be treated as the A pin for
compatibility with most RS485 transceivers. Likewise, the
PA pin should be matched up with the B signal in RS485.
Further discussion about this can be found in section “Bus
Pins PA and PB Naming Convention.”
Twisted pair cables with characteristic impedance of 120Ω
or 100Ω can be used. Shielded cable is recommended
for the highest electromagnetic compatibility (EMC), but
unshielded cable like CAT-5e works well. Untwisted pair
cables (UTP) should be avoided. Both ends of a cable
should be terminated differentially with resistors that
match the cable’s impedance, as illustrated in Figure 10.
1
M12 SOCKET
1
PA (A – Green Wire)
CNTR-N
(Repeater Direction Control)
5
The PROFIBUS standard only specifies the use of a 9-pin
D-sub connector for stations and cables. A commonly
used alternative is the 5-pin “B-coded” M12 circular connectors (IEC 947-5-2). In all cases, the female side of the
connector is located in the station, while the cable uses
the male end. Connector diagrams are shown in Figure 17
and pin designations are shown in Table 3.
PB (B – Red Wire)
5
9
9-PIN D-SUB
28767 F16
Figure 17. Connector Pin Allocations
Sometimes bus biasing resistors are used for nonPROFIBUS RS485 installations to introduce a high level
(IDLE state) on the bus when nothing is driving it. An
example of such a network is shown in Figure 181. Here
the three resistors (620Ω, 130Ω, and 620Ω) replace the
single 120Ω differential resistor in one location only.
28767fa
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23
LTC2876/LTC2877
Applications Information
5V
due to the overvoltage-tolerant design of the LTC2876/
LTC2877, as illustrated in Figure 15.
620Ω
LTC2876
OR
LTC2877
130Ω
120Ω
BUS BIAS
RESISTORS
AT ONE END
620Ω
LTC2876
OR
LTC2877
28767 F17
Figure 18. Using the LTC2876/LTC2877 in an RS485 Network
(Not PROFIBUS) with Optional Bus Bias Resistors
Unlike PROFIBUS, the biasing network is not part of the
RS485 standard. Although the LTC2876 and LTC2877
are compatible with this biasing arrangement, the internal failsafe feature eliminates the need for it, since an
undriven bus triggers a failsafe condition. In extremely
noisy environments the resistor biasing helps reinforce
the failsafe condition.
VL Logic Supply
A separate logic supply pin VL allows the LTC2877 to
interface with any logic signal from 1.65V to 5.5V. All
logic I/Os use VL as their high supply. It is recommended
that VL does not exceed VCC during operation. If VL does
exceed VCC, no damage will occur but the VL supply current
could increase about 300µA, depending on the operating
configuration and the state of the device. If VL is not connected to VCC, bypass VL with a 0.1µF capacitor to GND.
The driver is disabled and pins PB and PA are undriven
when VL or VCC is grounded or disconnected.
3.3V Operation
The LTC2876 and LTC2877 can be used with a supply
voltage as low as 3.0V in RS485 installations. Reducing
the supply voltage reduces the driver output signal swing
below what is specified in the RS485 standard but still
produces signals much larger than the 200mV minimum
signal swing required at the receiver input. A plot in the
Typical Characteristics section shows the driver output
signal for 3.3V and 5V supply voltages.
3.3V-powered LTC2876/LTC2877 devices can be mixed
with other RS485 transceivers running from 5V on the same
network as shown in Figure 20. There is no concern for
the higher voltage of a 5V node overdriving the 3.3V node
24
One advantage to using a lower supply voltage is reduced
VCC current draw. VCC supply currents are roughly proportional to the applied supply voltage when the LTC2876/
LTC2877 is driving loads. The Typical Characteristics
section shows the typical power supply currents versus
transmission rates for 3.3V and 5V supplies.
PROFIBUS installations that use the LTC2876/LTC2877
with supply voltages less than 4.5V, may fall out of compliance to the PROFIBUS specification.
High Speed Considerations
A ground plane layout with a 1µF bypass capacitor placed
less than 7mm away from VCC is recommended. The PC
board traces connected to signal PB and PA should be
symmetrical and as short as possible to maintain good
differential signal integrity. To minimize capacitive effects,
the differential signals should be separated by more than
the width of a trace and should not be routed on top of
each other if they are on different signal planes.
Care should be taken to route the outputs away from the
sensitive inputs to reduce feedback effects that might
cause noise, jitter, and even oscillations. For example, DI
and RO should not be routed next to each other or next
to PB and PA.
Logic inputs have a typical hysteresis of about 150mV to
provide noise immunity. Fast edges on the outputs can
cause glitches in the ground and power supplies which are
exacerbated by capacitive loading. If a logic input is held
near its threshold (typically VCC /2 or VL/2), a noise glitch
from a driver transition may exceed the hysteresis levels
on the logic and data input pins, causing an unintended
state change. This can be avoided by maintaining normal
logic levels on the pins and by slewing inputs faster than
1V/µs. Good supply decoupling and proper driver termination also reduces glitches caused by driver transitions.
References
1
“Application Guidelines for TIA/EIA-485-A”: TSB-89-A,
TIA Telecommunications System Bulletin, January 2006.
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LTC2876/LTC2877
Applications Information
VCC
VL
4.5V to 5.5V
LTC2876
VCC
9-PIN D-SUB
CONNECTOR
(FEMALE)
1µF
VCC
RO
PB
µC
1
PB
0.1µF
VL
3
PA
VCC
LTC2877
1µF
PB
PB
SENSOR
8
9-PIN D-SUB
CONNECTOR
(FEMALE)
1
6
RE
PA
DI
PA
3
8
PA
5
DE
5
DE
GND
GND
GND
GND
(a)
6
VCC
RO
µC
DI
4.5V to 5.5V
6
RE
SENSOR
VCC
1.65V to 5.5V
(b)
1
390Ω
3
220Ω
PROFIBUS CABLE
(ZO = 150Ω)
390Ω
6
1
B
8
220Ω
8
A
5
9-PIN D-SUB
CONNECTOR
(MALE)
SHIELD
390Ω
390Ω
TERMINATION RESISTOR STRINGS
SWITCHED IN TO SIGNAL LINES
IF LOCATED AT BUS END
3
5
9-PIN D-SUB
CONNECTOR
(MALE)
(c)
28767 F18
Figure 19. Complete Configuration for PROFIBUS Operation Using the (a) LTC2876, or (b) LTC2877 and
(c) the Cable with Termination Resistors
28767fa
For more information www.linear.com/LTC2876
25
LTC2876/LTC2877
Applications Information
3V TO 5.5V
3V TO 5.5V
VCC
PB
LTC2876/
LTC2877
A
120Ω
3.3V OR 5V
RS485
NODE
120Ω
B
PA
28767 F19
Figure 20. LTC2876/LTC2877 Operation as Low as 3V is Compatible with Other RS485
Devices, but with Reduced Output Signal Swing
TVS
TVS
PB
PB
PA
PA
LTC2876/
LTC2877
TVS
TVS: LITTLEFUSE SACB30
TVS
28767 F21
Figure 21. Exceptionally Robust, Low-Capacitance, ±30V Tolerant, ±4kV IEC 61000
Bus Protection Against Surge, EFT, and ESD. (See Auxiliary Protection for Surge,
EFT, and ESD in the Applications Information Section for More Details)
26
28767fa
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LTC2876/LTC2877
Package Description
Please refer to http://www.linear.com/product/LTC2876#packaging for the most recent package drawings.
DD Package
8-Lead Plastic DFN (3mm × 3mm)
(Reference LTC
# 05-08-1698 Rev C)
DDDWG
Package
8-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1698 Rev C)
0.70 ±0.05
3.5 ±0.05
1.65 ±0.05
2.10 ±0.05 (2 SIDES)
PACKAGE
OUTLINE
0.25 ±0.05
0.50
BSC
2.38 ±0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
PIN 1
TOP MARK
(NOTE 6)
0.200 REF
3.00 ±0.10
(4 SIDES)
R = 0.125
TYP
5
0.40 ±0.10
8
1.65 ±0.10
(2 SIDES)
0.75 ±0.05
4
0.25 ±0.05
1
(DD8) DFN 0509 REV C
0.50 BSC
2.38 ±0.10
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON TOP AND BOTTOM OF PACKAGE
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27
LTC2876/LTC2877
Package Description
Please refer to http://www.linear.com/product/LTC2876#packaging for the most recent package drawings.
DD Package
Package
10-Lead Plastic DFNDD
(3mm
× 3mm)
10-Lead
DFN (3mm
(Reference
LTC DWGPlastic
# 05-08-1699
Rev C)× 3mm)
(Reference LTC DWG # 05-08-1699 Rev C)
0.70 ±0.05
3.55 ±0.05
1.65 ±0.05
2.15 ±0.05 (2 SIDES)
PACKAGE
OUTLINE
0.25 ±0.05
0.50
BSC
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
3.00 ±0.10
(4 SIDES)
R = 0.125
TYP
6
0.40 ±0.10
10
1.65 ±0.10
(2 SIDES)
PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
CHAMFER
PIN 1
TOP MARK
(SEE NOTE 6)
0.200 REF
5
0.75 ±0.05
0.00 – 0.05
1
(DD) DFN REV C 0310
0.25 ±0.05
0.50 BSC
2.38 ±0.10
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
28
28767fa
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LTC2876/LTC2877
Package Description
Please refer to http://www.linear.com/product/LTC2876#packaging for the most recent package drawings.
MS8E Package
8-Lead Plastic
MSOP
, Exposed Die Pad
MS8E
Package
(Reference
LTC MSOP,
DWG # 05-08-1662
Rev Pad
K)
8-Lead
Plastic
Exposed Die
(Reference LTC DWG # 05-08-1662 Rev K)
BOTTOM VIEW OF
EXPOSED PAD OPTION
1.88
(.074)
1
1.88 ±0.102
(.074 ±.004)
0.29
REF
1.68
(.066)
0.889 ±0.127
(.035 ±.005)
0.05 REF
5.10
(.201)
MIN
DETAIL “B”
CORNER TAIL IS PART OF
DETAIL “B” THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
NO MEASUREMENT PURPOSE
1.68 ±0.102 3.20 – 3.45
(.066 ±.004) (.126 – .136)
8
3.00 ±0.102
(.118 ±.004)
(NOTE 3)
0.65
(.0256)
BSC
0.42 ±0.038
(.0165 ±.0015)
TYP
8
7 6 5
0.52
(.0205)
REF
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
4.90 ±0.152
(.193 ±.006)
DETAIL “A”
0° – 6° TYP
GAUGE PLANE
0.53 ±0.152
(.021 ±.006)
DETAIL “A”
1
2 3
4
1.10
(.043)
MAX
0.86
(.034)
REF
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
0.65
(.0256)
NOTE:
BSC
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD
SHALL NOT EXCEED 0.254mm (.010") PER SIDE.
0.1016 ±0.0508
(.004 ±.002)
MSOP (MS8E) 0213 REV K
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29
LTC2876/LTC2877
Package Description
Please refer to http://www.linear.com/product/LTC2876#packaging for the most recent package drawings.
MSE Package
10-Lead Plastic MSOP, Exposed Die Pad
MSE
Package
(Reference LTC
DWG
# 05-08-1664 Rev I)
10-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1664 Rev I)
BOTTOM VIEW OF
EXPOSED PAD OPTION
1.88 ±0.102
(.074 ±.004)
5.10
(.201)
MIN
1
0.889 ±0.127
(.035 ±.005)
1.68 ±0.102
(.066 ±.004)
0.05 REF
10
0.305 ± 0.038
(.0120 ±.0015)
TYP
RECOMMENDED SOLDER PAD LAYOUT
3.00 ±0.102
(.118 ±.004)
(NOTE 3)
DETAIL “B”
CORNER TAIL IS PART OF
DETAIL “B” THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
NO MEASUREMENT PURPOSE
10 9 8 7 6
DETAIL “A”
0° – 6° TYP
1 2 3 4 5
GAUGE PLANE
0.53 ±0.152
(.021 ±.006)
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.86
(.034)
REF
1.10
(.043)
MAX
0.17 – 0.27
(.007 – .011)
TYP
0.50
(.0197)
BSC
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD
SHALL NOT EXCEED 0.254mm (.010") PER SIDE.
30
0.497 ±0.076
(.0196 ±.003)
REF
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
4.90 ±0.152
(.193 ±.006)
0.254
(.010)
0.29
REF
1.68
(.066)
3.20 – 3.45
(.126 – .136)
0.50
(.0197)
BSC
1.88
(.074)
0.1016 ±0.0508
(.004 ±.002)
MSOP (MSE) 0213 REV I
28767fa
For more information www.linear.com/LTC2876
LTC2876/LTC2877
Revision History
REV
DATE
DESCRIPTION
A
08/16
Changed test condition for tPLHR and tPHLR
PAGE NUMBER
5
28767fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection
of its circuits
as described
herein will not infringe on existing patent rights.
For more
information
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31
LTC2876/LTC2877
Typical Application
3500VRMS Isolated PROFIBUS Node with Termination
ISOLATED
5VIN
3V TO
5.5V
RO
D R
DI
A6
A5
A4
B1
B2
B3
A3
A2
A1
B4
B5
B6
VCC1
VL1
ON1
OUTD
OUTE
OUTF
INC
INB
INA
EOUTD
GND1
GND1
ISOLATION BARRIER
LTM2892-S
VCC2
VL2
ON2
IND
INE
INF
OUTC
OUTB
OUTA
EOUTA
GND2
GND2
J6
J5
J4
J1
J2
J3
H3
H2
H1
H4
H5
H6
8
VCC
LTC2876
390Ω
1 RO
PB
4
6
3
2 RE
7
4 DI
3 DE
1
220Ω
PA
GND
2
M12
CONNECTOR
(FEMALE)
390Ω
5
ISOLATED
GROUND
28767 TA02
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
LTC2862/LTC2863/ ±60V Fault Protected 3V to 5.5V RS485/RS422 Transceivers
LTC2864/LTC2865
±60V Tolerant, ±15kV ESD, 250kbps or 20Mbps
LTC2856/LTC2857/ 5V 20Mbps and Slew Rate Limited 15kV RS485/RS422
LTC2858
Transceivers
±15kV ESD, 250kbps or 20Mbps
LTC2850/LTC2851/ 3.3V 20Mbps RS485 Transceivers
LTC2852
±15kV ESD
LTC2854/LTC2855
±25kV ESD (LTC2854), ±15kV ESD (LTC2855)
3.3V 20Mbps RS485 Transceivers with Integrated Switchable
Termination
LTC2859, LTC2861 5V 20Mbps and Slew Rate Limited RS485 Transceivers
±15kV ESD
LTM2881
Complete 3.3V or 5V Isolated RS485 µModule Transceiver +
Power, and Switchable Integrated Termination Resistor
2500VRMS Isolation, with Integrated Isolated DC/DC Converter,
1W Power, Low EMI, ±15kV ESD, 30kV/µs Transient Immunity
LTM2892
3500VRMS 6-Channel Digital Isolator
3500VRMS Isolation in a Small Package with Temperature Ratings
Up to 125°C
32 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LTC2876
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LTC2876
28767fa
LT 0816 REV A • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 2016