AD ADM2795EBRWZ Robust 5 kv rms isolated rs-485/rs-422 transceiver with level 4 emc and full â±42 v protection Datasheet

Robust 5 kV RMS Isolated RS-485/RS-422 Transceiver
with Level 4 EMC and Full ±42 V Protection
ADM2795E
Data Sheet
FEATURES
APPLICATIONS
5 kV rms isolated RS-485/RS-422 transceiver
±42 V ac/dc peak fault protection on RS-485 bus pins
Certified Level 4 EMC protection on RS-485 A, B bus pins
IEC 61000-4-5 surge protection (±4 kV)
IEC 61000-4-4 electrical fast transient (EFT) protection (±2 kV)
IEC 61000-4-2 electrostatic discharge (ESD) protection
±8 kV contact discharge
±15 kV air discharge
IEC 61000-4-6 conducted radio frequency (RF) immunity
(10 V/m rms)
Certified IEC 61000-4-x immunity across isolation barrier
IEC 61000-4-2 ESD, IEC 61000-4-4 EFT, IEC 61000-4-5 surge,
IEC 61000-4-6 conducted RF immunity, IEC 61000-4-3
radiated immunity, IEC 61000-4-8 magnetic immunity
RS-485 A, B pins human body model (HBM) ESD protection:
>±30 kV
Safety and regulatory approvals (pending)
CSA Component Acceptance Notice 5A, DIN V VDE V 0884-10,
UL 1577, CQC11-471543-2012
TIA/EIA RS-485/RS-422 compliant over full supply range
3 V to 5.5 V operating voltage range on VDD2
1.7 V to 5.5 V operating voltage range on VDD1 logic supply
Common-mode input range of −25 V to +25 V
High common-mode transient immunity: >75 kV/μs
Robust noise immunity (tested to the IEC 62132-4 standard)
Passes EN55022 Class B radiated emissions by 6 dBµV/m margin
Receiver short-circuit, open-circuit, and floating input fail-safe
Supports 256 bus nodes (96 kΩ receiver input impedance)
−40°C to +125°C temperature option
Glitch free power-up/power-down (hot swap)
Heating, ventilation, and air conditioning (HVAC) networks
Industrial field buses
Building automation
Utility networks
GENERAL DESCRIPTION
The ADM2795E is a 5 kV rms signal isolated RS-485 transceiver
that features up to ±42 V of ac/dc peak bus overvoltage fault protection on the RS-485 bus pins. The device integrates Analog Devices,
Inc., iCoupler® technology to combine a 3-channel isolator, RS-485
transceiver, and IEC electromagnetic compatibility (EMC)
transient protection in a single package. The ADM2795E is a
RS-485/RS-422 transceiver that integrates IEC 61000-4-5 Level 4
surge protection, allowing up to ±4 kV protection on the RS-485
bus pins (A and B). The device has IEC 61000-4-4 Level 4 EFT
protection up to ±2 kV and IEC 61000-4-2 Level 4 ESD protection
on the bus pins, allowing this device to withstand up to ±15 kV on
the transceiver interface pins without latching up. This device
has an extended common-mode input range of ±25 V to improve
data communication reliability in noisy environments. The
ADM2795E is capable of operating over wide power supply
ranges, with a 1.7 V to 5.5 V VDD1 power supply range, allowing
interfacing to low voltage logic supplies. The ADM2795E is also
fully TIA/EIA RS-485/RS-422 compliant when operated over a
3 V to 5.5 V VDD2 power supply. The device is fully characterized
over an extended operating temperature range of −40°C to +125°C,
and is available in a 16-lead, wide-body SOIC package.
FUNCTIONAL BLOCK DIAGRAM
VDD1
VDD2
DIGITAL ISOLATOR
RS-485
TRANSCEIVER
ADM2795E
RxD
RE
EMC
TRANSIENT
PROTECTION
CIRCUIT
DE
A
B
GND1
GND2
ISOLATION
BARRIER
14129-001
TxD
Figure 1.
Rev. 0
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ADM2795E
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Integrated and Certified IEC EMC Solution .......................... 15
Applications ....................................................................................... 1
Overvoltage Fault Protection .................................................... 16
General Description ......................................................................... 1
±42 V Miswire Protection ......................................................... 16
Functional Block Diagram .............................................................. 1
RS-485 Network Biasing and Termination ............................. 16
Revision History ............................................................................... 2
IEC ESD, EFT, and Surge Protection ....................................... 17
Specifications..................................................................................... 3
IEC Conducted, Radiated, and Magnetic Immunity............. 21
Timing Specifications .................................................................. 4
Applications Information .............................................................. 23
Insulation and Safety-Related Specifications ............................ 5
Radiated Emissions and PCB Layout ...................................... 23
Package Characteristics ............................................................... 5
Noise Immunity .......................................................................... 23
Regulatory Information ............................................................... 5
Fully RS-485 Compliant over an Extended ±25 V CommonMode voltage Range ................................................................... 23
DIN V VDE V 0884-10 (VDE V 0884-10) Insulation
Characteristics (Pending) ............................................................ 6
1.7 V to 5.5 V VDD1 Logic Supply.............................................. 23
Absolute Maximum Ratings ............................................................ 7
Truth Tables................................................................................. 24
Thermal Resistance ...................................................................... 7
Receiver Fail-Safe ....................................................................... 24
ESD Caution .................................................................................. 7
RS-485 Data Rate and Bus Capacitance .................................. 24
Pin Configuration and Function Descriptions ............................. 8
Insulation Wear Out .................................................................. 24
Typical Performance Characteristics ............................................. 9
Hot Swap Capability................................................................... 25
Test Circuits ..................................................................................... 13
Robust Half-Duplex RS-485 Network ..................................... 25
Switching Characteristics .......................................................... 14
Outline Dimensions ....................................................................... 27
Theory of Operation ...................................................................... 15
Ordering Guide .......................................................................... 27
RS-485 with Robustness ............................................................ 15
REVISION HISTORY
10/2016—Revision 0: Initial Version
Rev. 0 | Page 2 of 27
Data Sheet
ADM2795E
SPECIFICATIONS
1.7 V ≤ VDD1 ≤ 5.5 V, 3 V ≤ VDD2 ≤ 5.5 V, TA = −40°C to +125°C. All min/max specifications apply over the entire recommended operation
range, unless otherwise noted. All typical specifications at TA = 25°C, VDD1 = VDD2 = 5.0 V, unless otherwise noted.
Table 1.
Parameter
SUPPLY CURRENT
Power Supply Current
Logic Side
TxD/RxD Data Rate = 2.5 Mbps
Bus Side
TxD/RxD Data Rate = 2.5 Mbps
Supply Current in Shutdown Mode
DRIVER
Differential Outputs
Differential Output Voltage
Symbol
Input Capacitance (A, B)
Line Input Resistance
Typ
IDD1
IDD2
Max
Unit
Test Conditions/Comments
10
10
12
90
130
mA
mA
mA
mA
mA
Unloaded output, DE = VDD1, RE = 0 V
Unloaded output, DE = VDD1, RE = 0 V
Unloaded output, DE = VDD1, RE = 0 V
Unloaded output, DE = VDD1, RE = 0 V
DE = VDD1, RE = 0 V, VDD2 = 5.5 V,
R = 27 Ω, see Figure 27
DE = VDD1, RE = 0 V, VDD2 = 5.5 V,
R = 27 Ω, see Figure 27
DE = VDD1, RE = 0 V, VDD2 = 3.0 V,
R = 27 Ω, see Figure 27
DE = 0 V, RE = VDD1
94
mA
46
mA
ISHDN
10
mA
1.5
5.0
V
2.1
5.0
V
1.5
5.0
V
2.1
5.0
V
∆|VOD|
0.2
V
VDD2 ≥ 3.0 V, R = 27 Ω or 50 Ω,
see Figure 27
VDD2 ≥ 4.5 V, R = 27 Ω or 50 Ω,
see Figure 27
VDD2 ≥ 3.0 V, VCM = −25 V to +25 V, see
Figure 28
VDD2 ≥ 4.5 V, VCM = −25 V to +25 V, see
Figure 28
R = 27 Ω or 50 Ω, see Figure 27
VOC
∆|VOC|
3.0
0.2
V
V
R = 27 Ω or 50 Ω, see Figure 27
R = 27 Ω or 50 Ω, see Figure 27
+250
+250
mA
mA
−42 V ≤ VSC ≤ +42 V1
−42 V ≤ VSC ≤ +42 V1
0.33 × VDD1
V
V
µA
1.7 V ≤ VDD1 ≤ 5.5 V
1.7 V ≤ VDD1 ≤ 5.5 V
0 V ≤ VIN ≤ VDD1
mV
mV
mA
mA
pF
kΩ
−25 V ≤ VCM ≤ +25 V
−25 V ≤ VCM ≤ +25 V
DE = 0 V, VDD2 = 0 V/5 V, VIN = ±25 V
DE = 0 V, VDD2 = 0 V/5 V, VIN = ±42 V
TA = 25°C, see Figure 17
−25 V ≤ VCM ≤ +25 V, up to 256 nodes
supported
|VOD|
|VOD3|
Change in Differential Output Voltage
for Complementary Output States
Common-Mode Output Voltage
Change in Common-Mode Output
Voltage for Complementary Output
States
Short-Circuit Output Current
VOUT = Low
VOUT = High
Logic Inputs (DE, RE, TxD)
Input Threshold Low
Input Threshold High
Input Current
RECEIVER
Differential Inputs
Differential Input Threshold Voltage
Input Voltage Hysteresis
Input Current (A, B)
Min
IOSL
IOSH
−250
−250
VIL
VIH
ITxD
0.7 VDD1
VTH
VHYS
II
CAB
RIN
+1
−200
−125
30
−1.0
−1.0
−30
+1.0
+1.0
150
96
Rev. 0 | Page 3 of 27
ADM2795E
Data Sheet
Parameter
Logic Outputs
Output Voltage Low
Output Voltage High
Short-Circuit Current
Three-State Output Leakage Current
Symbol
Min
VOLRxD
VOHRxD
VDD1 − 0.2
2
Max
Unit
Test Conditions/Comments
0.2
V
V
mA
µA
IORxD = 3.0 mA, VA − VB = −0.2 V
IORxD = −3.0 mA, VA − VB = 0.2 V
VOUT = GND or VDD1, RE = 0 V
RE = VDD1, RxD = 0 V or VDD1
kV/µs
VCM ≥1 kV, transient magnitude
≥800 V
100
±2
IOZR
COMMON-MODE TRANSIENT IMMUNITY2
1
Typ
75
125
VSC is the short-circuit voltage at the RS-485 A or B bus pin.
Common-mode transient immunity is the maximum common-mode voltage slew rate that can be sustained while maintaining specification-compliant operation. VCM
is the common-mode potential difference between the logic and bus sides. The transient magnitude is the range over which the common mode is slewed. The
common-mode voltage slew rates apply to both rising and falling common-mode voltage edges.
TIMING SPECIFICATIONS
VDD1 = 1.7 V to 5.5 V, VDD2 = 3.0 V to 5.5 V, TA = TMIN to TMAX (−40°C to +125°C), unless otherwise noted.
Table 2.
Parameter
DRIVER1
Maximum Data Rate
Propagation Delay, tDPLH, tDPHL
Differential Skew, tSKEW
Rise/Fall Times, tR, tF
Enable Time, tZH, tZL
Disable Time, tHZ, tLZ
RECEIVER2
Propagation Delay, tPLH, tPHL
Skew, tSKEW
Enable Time
Disable Time
RxD Pulse Width Distortion
1
2
Min
Typ
Max
Unit
Test Conditions/Comments
30
10
40
500
500
500
50
130
2500
2500
Mbps
ns
ns
ns
ns
ns
RLDIFF = 54 Ω, CL1 = CL2 = 100 pF, see Figure 29 and Figure 33
RLDIFF = 54 Ω, CL1 = CL2 = 100 pF, see Figure 29 and Figure 33
RLDIFF = 54 Ω, CL1 = CL2 = 100 pF, see Figure 29 and Figure 33
RL = 110 Ω, CL = 50 pF, see Figure 30 and Figure 35
RL = 110 Ω, CL = 50 pF, see Figure 30 and Figure 35
120
140
4
10
10
200
220
40
50
50
40
ns
ns
ns
ns
ns
ns
CL = 15 pF, see Figure 31 and Figure 34, 10, VID ≥ ±1.5 V
CL = 15 pF, see Figure 31 and Figure 34, VID ≥ ±600 mV
CL = 15 pF, see Figure 31 and Figure 34, VID ≥ ±1.5 V
RL = 1 kΩ, CL = 15 pF, see Figure 32 and Figure 36
RL = 1 kΩ, CL = 15 pF, see Figure 32 and Figure 36
CL = 15 pF, see Figure 31 and Figure 34, VID ≥ ±1.5 V
2.5
See Figure 29 for the definition of RLDIFF.
Receiver propagation delay, skew, and pulse width distortion specifications are tested with a receiver differential input voltage (VID) of ≥±600 mV or ≥±1.5 V, as noted.
Rev. 0 | Page 4 of 27
Data Sheet
ADM2795E
INSULATION AND SAFETY-RELATED SPECIFICATIONS
For additional information, see www.analog.com/icouplersafety.
Table 3.
Parameter
Rated Dielectric Insulation Voltage
Minimum External Air Gap (Clearance)
Symbol
L(I01)
Value
5000
7.8
Unit
V rms
mm min
Minimum External Tracking (Creepage)
L(I02)
7.8
mm min
Minimum Clearance in the Plane of the Printed
Circuit Board (PCB Clearance)
L(PCB)
8.3
mm min
CTI
25.5
>400
II
µm min
V
Minimum Internal Gap (Internal Clearance)
Tracking Resistance (Comparative Tracking Index)
Material Group
Conditions
1 minute duration
Measured from input terminals to output terminals,
shortest distance through air
Measured from input terminals to output terminals,
shortest distance along body
Measured from input terminals to output terminals,
shortest distance through air, line of sight, in the PCB
mounting plane
Minimum distance through insulation
DIN IEC 112/VDE 0303 Part 1
Material Group (DIN VDE 0110, 1/89)
PACKAGE CHARACTERISTICS
Table 4.
Parameter
Resistance (Input to Output)1
Capacitance (Input to Output)1
Input Capacitance2
Input Capacitance, A and B Pins
IC Junction to Ambient Thermal Resistance
1
2
Symbol
RI-O
CI-O
CI
CAB
θJA
Min
Typ
1013
2.2
4.0
150
59.7
Max
Unit
Ω
pF
pF
pF
°C/W
Test Conditions/Comments
f = 1 MHz
TA = 25°C, see Figure 17
Thermocouple located at center of package underside
The device is considered a 2-terminal device: Pin 1 through Pin 8 are shorted together, and Pin 9 through Pin 16 are shorted together.
Input capacitance is from any digital input pin to ground.
REGULATORY INFORMATION
See Table 8 and the Insulation Wear Out section for details regarding recommended maximum working voltages for specific cross
isolation waveforms and insulation levels.
The ADM2795E is approved or pending approval by the organizations listed in Table 5.
Table 5. ADM2795E Approvals
UL (Pending)
Recognized Under UL 1577
Component Recognition
Program1
Single Protection, 5000 V rms
Isolation Voltage
File (Pending)
1
2
CSA (Pending)
Approved under CSA Component
Acceptance Notice 5A
VDE (Pending)
Certified according to DIN V VDE V 088410 (VDE V 0884-10):2006-122
CSA 60950-1-07+A1+A2 and IEC 60950-1
second edition +A1+A2:
Basic insulation at 780 V rms
(1103 V peak)
Reinforced insulation at 390 V rms
(552 V peak)
IEC 60601-1 Edition 3.1: basic insulation
(two means of patient protection
(MOPP)), 250 V rms (353 V peak)
CSA 61010-1-12 and IEC 61010-1 third
edition:
Basic insulation at 300 V rms mains, 780 V
secondary (1103 V peak)
Reinforced insulation at 300 V rms mains,
390 V secondary (552 V peak)
File (pending)
Reinforced insulation, VIORM = 849 V peak,
VIOSM = 8000 V peak
File 40011599
In accordance with UL 1577, each ADM2795E is proof tested by applying an insulation test voltage ≥ 6000 V rms for 1 sec.
In accordance with DIN V VDE V 0884-10, each ADM2795E is proof tested by applying an insulation test voltage ≥1592 V peak for 1 sec.
Rev. 0 | Page 5 of 27
CQC (Pending)
Certified by
CQC11-471543-2012,
GB4943.1-2011
Basic insulation at
780 V rms (1103 V peak)
Reinforced insulation at
389 V rms (552 V peak)
File (pending)
ADM2795E
Data Sheet
DIN V VDE V 0884-10 (VDE V 0884-10) INSULATION CHARACTERISTICS (PENDING)
This isolator is suitable for reinforced electrical isolation only within the safety limit data. Maintenance of the safety data must be ensured
by means of protective circuits.
An asterisk (*) on a package denotes VDE 0884 approval for a 849 V peak working voltage.
Table 6.
Description
Installation Classification per DIN VDE 0110 for
Rated Mains Voltage
≤150 V rms
≤300 V rms
≤400 V rms
Climatic Classification
Pollution Degree (DIN VDE 0110, see Table 3)
Maximum Working Insulation Voltage
Input to Output Test Voltage, Method b1
Input to Output Test Voltage, Method a
After Environmental Tests, Subgroup 1
After Input and/or Safety Test,
Subgroup 2/Subgroup 3
Highest Allowable Overvoltage
Reinforced Surge Isolation Voltage
Safety Limiting Values
Total Power Dissipation at TA = 25°C
Insulation Resistance at TS
Test Conditions/Comments
VIORM × 1.875 = VPR, 100% production tested, tm =
1 sec, partial discharge < 5 pC
Transient overvoltage, tTR = 10 sec
VPEAK = 12.8 kV, 1.2 µs rise time, 50 µs, 50% fall time
Maximum value allowed in the event of a failure,
see Figure 2
VIO = 500 V
SAFE LIMITING POWER (W)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
50
100
150
14129-002
0.2
AMBIENT TEMPERATURE (°C)
Unit
VIORM
VPR
I to IV
I to IV
I to III
40/125/21
2
849
1592
V peak
V peak
1274
1019
V peak
V peak
VIOTM
VIOSM
TS
7000
8000
150
V peak
V peak
°C
PS
RS
1.80
>109
W
Ω
VPR
1.8
0
Characteristic
VIORM × 1.5 = VPR, tm = 60 sec, partial discharge < 5 pC
VIORM × 1.2 = VPR, tm = 60 sec, partial discharge < 5 pC
2.0
0
Symbol
Figure 2. Thermal Derating Curve for RW-16 Wide Body [SOIC_W] Package,
Dependence of Safety Limiting Values with Ambient Temperature per
DIN V VDE V 0884-10
Rev. 0 | Page 6 of 27
Data Sheet
ADM2795E
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Table 8. Maximum Continuous Working Voltage1
Table 7.
Parameter
AC Voltage
Bipolar Waveform
Basic Insulation
Parameter
VDD1
VDD2
Digital Input/Output Voltage (DE, RE,
TxD, RxD)
Driver Output/Receiver Input Voltage
Operating Temperature Range
Storage Temperature Range
Maximum Junction Temperature
Continuous Total Power Dissipation
Lead Temperature
Soldering (10 sec)
Vapor Phase (60 sec)
Infrared (15 sec)
ESD (A, B Pins Tested to GND2)
IEC 61000-4-2 Contact Discharge
IEC 62000-4-2 Air Discharge
EFT (A, B Pins Tested to GND2)
IEC 61000-4-4 Level 4 EFT Protection
Surge (A, B Pins Tested to GND2)
IEC 61000-4-5 Level 4 Surge
Protection
EMC Performance from A, B Bus Pins
Across the Isolation Barrier to GND1
ESD
IEC 61000-4-2 Contact Discharge
IEC 61000-4-2 Air Discharge
EFT
IEC 61000-4-4
Surge
IEC 61000-4-5
HBM ESD Protection (A, B Pins Tested to
GND2)
HBM ESD Protection (All Pins)
Field Induced Charged Device Model
ESD (FICDM)
Rating
−0.5 V to +7 V
−0.5 V to +7 V
−0.3 V to VDD1 + 0.3 V
Reinforced
Insulation
±48 V
−40°C to +125°C
−65°C to +150°C
150°C
405 mW
Unipolar Waveform
Basic Insulation
Reinforced
Insulation
300°C
215°C
220°C
±8 kV
±15 kV
DC Voltage
Basic Insulation
Max
Unit
Reference Standard2
849
V peak
768
V peak
50-year minimum
insulation lifetime
Lifetime limited by
package creepage
maximum approved
working voltage per
IEC 60950-1
1698
V peak
885
V peak
1092
V peak
543
V peak
±2 kV
±4 kV
Reinforced
Insulation
±9 kV
±8 kV
50-year minimum
insulation lifetime
Lifetime limited by
package creepage
maximum approved
working voltage per
IEC 60950-1
Lifetime limited by
package creepage
maximum approved
working voltage per
IEC 60950-1
Lifetime limited by
package creepage
maximum approved
working voltage per
IEC 60950-1
1
The maximum continuous working voltage refers to the continuous voltage
magnitude imposed across the isolation barrier. See the Insulation Wear Out
section for more details.
2
Insulation lifetime for the specified test condition is greater than 50 years.
±2 kV
THERMAL RESISTANCE
±4 kV
>±30 kV
Thermal performance is directly linked to PCB design and
operating environment. Careful attention to PCB thermal
design is required.
±6 kV
±1.25 kV
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
θJA is the natural convection junction to ambient thermal resistance
measured in a one cubic foot sealed enclosure. θJC is the junction to
case thermal resistance.
Table 9. Thermal Resistance
Package Type
RW-16
1
θJA1
59.7
θJC1
28.3
Unit
°C/W
Thermal impedance simulated values are based on a JEDEC 2S2P thermal
test board with no vias. See JEDEC JESD51.
ESD CAUTION
Rev. 0 | Page 7 of 27
ADM2795E
Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
16 VDD2
VDD1 1
15 GND2
2
TxD 3
DE 4
ADM2795E
14 B
13 VDD2
RxD 6
TOP VIEW
(Not to Scale) 12 GND2
11 A
NIC 7
10 GND2
RE 5
GND1 8
9
GND2
NOTES
1. NIC = NOT INTERNALLY CONNECTED.
14129-003
GND1
Figure 3. Pin Configuration
Table 10. Pin Function Descriptions
Pin No.
1
2
3
4
Mnemonic
VDD1
GND1
TxD
DE
5
RE
6
7
8
9
10
11
RxD
NIC
GND1
GND2
GND2
A
12
13
14
GND2
VDD2
B
15
16
GND2
VDD2
Description
1.7 V to 5.5 V Flexible Logic Interface Supply.
Ground 1, Logic Side.
Transmit Data Input. Data to be transmitted by the driver is applied to this input.
Driver Output Enable. A high level on this pin enables the driver differential outputs, A and B. A low level places
them into a high impedance state.
Receiver Enable Input. This pin is an active low input. Driving this input low enables the receiver, and driving it high
disables the receiver.
Receiver Output Data. This output is high when (A – B) > −30 mV and low when (A – B) < –200 mV.
Not Internally Connected. This pin is not internally connected.
Ground 1, Logic Side.
Isolated Ground 2, Bus Side.
Isolated Ground 2, Bus Side.
Noninverting Driver Output/Receiver Input. When the driver is disabled, or when VDD1 or VDD2 is powered down,
Pin A is put into a high impedance state to avoid overloading the bus.
Isolated Ground 2, Bus Side.
3 V to 5.5 V Power Supply. Pin 13 must be connected externally to Pin 16.
Inverting Driver Output/Receiver Input. When the driver is disabled, or when VDD1 or VDD2 is powered down, Pin B is
put into a high impedance state to avoid overloading the bus.
Isolated Ground 2, Bus Side.
3 V to 5.5 V Power Supply. Pin 16 must be connected externally to Pin 13.
Rev. 0 | Page 8 of 27
Data Sheet
ADM2795E
TYPICAL PERFORMANCE CHARACTERISTICS
4.5
90
SUPPLY CURRENT (mA)
80
70
60
IDD2, 120Ω LOAD
50
40
30
IDD2, NO LOAD
20
IDD1
0
–40
–20
0
20
40
60
80
100
120
TEMPERATURE (°C)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–40
14129-004
10
VDD1 = VDD2 = 5.5V
4.0
–20
0
20
40
60
80
100
14129-007
VDD1 = VDD2 = 5.5 V
IDD2, 54Ω LOAD
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
100
120
TEMPERATURE (°C)
Figure 4. Supply Current (ICC) vs. Temperature at RL = 54 Ω, 120 Ω, and No
Load; Data Rate = 2.5 Mbps, VDD1 = 5.5 V, VDD2 = 5.5 V
Figure 7. Driver Differential Output Voltage vs. Temperature
60
0
VDD1 = 1.7V, VDD2 = 3.0V
–0.02
50
DRIVER OUTPUT CURRENT (A)
40
IDD2, 120Ω LOAD
30
20
IDD2, NO LOAD
IDD1
–20
–0.08
–0.10
–0.12
–0.14
0
20
40
60
80
100
120
TEMPERATURE (°C)
–0.16
DRIVER OUTPUT HIGH VOLTAGE (V)
Figure 8. Driver Output Current vs. Driver Output High Voltage
Figure 5. Supply Current (ICC) vs. Temperature at RL = 54 Ω, 120 Ω, and No
Load; Data Rate = 2.5 Mbps, VDD1 = 1.7 V, VDD2 = 3.0 V
0.14
0.01
VDD1 = 1.7V,
VDD2 = 3.0V
0.12
DRIVER OUTPUT CURRENT (A)
–0.04
–0.09
–0.14
VDD1 = 4.5V,
VDD2 = 4.5V
–0.19
VDD1 = 5.5V,
VDD2 = 5.5V
–0.24
–0.29
0.10
VDD1 = 1.7V, VDD2 = 3.0V
PIN A
VDD1 = 1.7V, VDD2 = 3.0V
PIN B
VDD1 = 5.5V, VDD2 = 5.5V
PIN A
VDD1 = 5.5V, VDD2 = 5.5V
PIN B
0.08
0.06
0.04
–0.39
0
1
2
3
4
5
DIFFERENTIAL OUTPUT VOLTAGE (V)
6
0
0
5
10
15
20
25
DRIVER OUTPUT LOW VOLTAGE (V)
Figure 9. Driver Output Current vs. Driver Output Low Voltage
Figure 6. Driver Output Current vs. Differential Output Voltage
Rev. 0 | Page 9 of 27
14129-009
0.02
–0.34
14129-006
DRIVER OUTPUT CURRENT (A)
–0.06
–25
–24
–23
–22
–21
–20
–19
–18
–17
–16
–15
–14
–13
–12
–11
–10
–9
–8
–7
–6
–5
–4
–3
–2
–1
0
1
2
3
4
5
6
0
–40
VDD1 = 1.7V, VDD2 = 3.0V
PIN A
VDD1 = 1.7V, VDD2 = 3.0V
PIN B
VDD1 = 5.5V, VDD2 = 5.5V
PIN A
VDD1 = 5.5V, VDD2 = 5.5V
PIN B
–0.04
14129-008
10
14129-005
SUPPLY CURRENT (mA)
IDD2, 54Ω LOAD
Data Sheet
45
36
VDD1 = VDD2 = 5V
VDD1 = VDD2 = 5.5V
35
RECEIVER OUTPUT CURRENT (mA)
40
34
33
tDPLH
tDPHL
32
31
30
29
28
35
30
25
20
15
10
5
27
0
–20
0
20
40
60
80
100
120
TEMPERATURE (°C)
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
14129-013
26
–40
14129-010
DRIVER DIFFERENTIAL PROPAGATION DELAY (ns)
ADM2795E
5.0
RECEIVER OUTPUT LOW VOLTAGE (V)
Figure 13. Receiver Output Current vs. Receiver Output Low Voltage
Figure 10. Driver Differential Propagation Delay vs. Temperature
6
C1
VOD
M1
M1 2.00V
A CH1
2.12V
100ns
3
2
VDD1 = 1.8V,
VDD2 = 3.3V
1
Figure 11. Driver Propagation Delay (Oscilloscope)
5
65
35
TEMPERATURE (°C)
–25
95
125
Figure 14. Receiver Output High Voltage vs. Temperature
60
RECEIVER OUTPUT LOW VOLTAGE (V)
VDD1 = VDD2 = 5V
–60
–50
–40
–30
–20
0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
RECEIVER OUTPUT HIGH VOLTAGE (V)
4.5
5.0
14129-012
–10
Figure 12. Receiver Output Current vs. Receiver Output High Voltage
Rev. 0 | Page 10 of 27
IRxD = –1mA
50
40
VDD1 = 1.8V,
VDD2 = 3.3V
30
VDD1 = 5.0V,
VDD2 = 5.0V
20
10
0
–55
–25
5
35
65
TEMPERATURE (°C)
95
125
Figure 15. Receiver Output Low Voltage vs. Temperature
14129-015
–70
RECEIVER OUTPUT CURRENT (mA)
IRxD = –1mA
4
0
–55
14129-011
C1 2.0V/DIV 1MΩ BW: 500M
VDD1 = 5.0V,
VDD2 = 5.0V
5
14129-014
RECEIVER OUTPUT HIGH VOLTAGE (V)
TxD
Data Sheet
ADM2795E
140
tPLH
B
2
VOD
M1
RxD
3
2.0V/DIV
2.0V/DIV
2.0V/DIV
1.4V
1MΩ BW: 500M
1MΩ BW: 500M
1MΩ BW: 500M
100ns
A CH3
2.56V
100ns/DIV
1.0ns/pt
tPHL
100
80
60
40
20
0
–55
–25
14129-016
C1
C2
C3
M1
120
95
125
Figure 19. Receiver Propagation Delay vs. Temperature
Figure 16. Receiver Propagation Delay (Oscilloscope)
250
INPUT CAPACITANCE (A, B) (pF)
5
65
35
TEMPERATURE (°C)
14129-019
RECEIVER PROPAGATION DELAY (ns)
A
A
2
B
PIN B
200
PIN A
VOD
150
M1
100
RxD
50
15
35
55
75
95
115 125 130 140
JUNCTION TEMPERATURE (°C)
0.14
70
0.12
SHORT-CIRCUIT CURRENT (A)
80
60
50
EN55022
40
EN55022B
30
20
100M
FREQUENCY (Hz)
0.08
0.06
0.04
VDD1 = 1.7V, VDD2 = 3.0V
PIN A
VDD1 = 1.7V, VDD2 = 3.0V
PIN B
VDD1 = 5.5V, VDD2 = 5.5V
PIN A
VDD1 = 5.5V, VDD2 = 5.5V
PIN B
0
1G
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
0
30M
2.56V
1MΩ BW: 500M OFFSET: 25.0V A CH3
100ns/DIV
1MΩ BW: 500M OFFSET: 25.0V
1.0ns/pt
B
1MΩ W: 500M
100ns
0.10
0.02
14129-018
10
1.0V
1.0V
2.0V/DIV
600mV
Figure 20. Receiver Performance with Input Common-Mode Voltage of 25 V
Figure 17. Input Capacitance (A, B) vs. Junction Temperature
QUASI PEAK LEVEL (dBµV/m)
C1
C2
C3
M1
14129-020
–5
PIN VOLTAGE (V)
Figure 18. Radiated Emissions Profile with 120 pF Capacitor to GND1 on the
RxD Pin (Horizontal Scan, Data Rate = 2.5 Mbps, VDD1 = VDD2 = 5.0 V)
Rev. 0 | Page 11 of 27
Figure 21. Short-Circuit Current over Fault Voltage Range
14129-021
0
–55 –40 –25
14129-017
3
ADM2795E
Data Sheet
40
30
25
20
15
10
0
100k
1M
10M
DPI FREQUENCY (Hz)
100M
1G
14129-022
5
RECEIVER OUTPUT (RxD) RISE/FALL TIME (ns)
POWER (dBm)
35
30
25
20
15
10
5
1G
POWER (dBm)
35
30
25
20
15
10
1G
14129-024
5
100M
0.25
0.50
1.00
2.00
2.50
60
50
FALL TIME
40
RISE TIME
30
20
10
100
1000
Figure 26. Receiver Output (RxD) Rise/Fall Time vs. Load Capacitance
40
10M
DPI FREQUENCY (Hz)
0
LOAD CAPACITANCE (pF)
45
1M
100
10
Figure 23. DPI IEC 62132-4 Noise Immunity with 100 nF Decoupling on VDD1
0
100k
200
0
14129-023
100M
300
Figure 25. Receiver Input Differential Voltage (VID) vs. Signaling Rate
40
10M
DPI FREQUENCY (Hz)
400
SIGNALING RATE (Mbps)
45
1M
500
0
Figure 22. DPI IEC 62132-4 Noise Immunity with 100 nF and 10 µF
Decoupling on VDD1
0
100k
600
14129-126
POWER (dBm)
35
700
14129-025
RECEIVER INPUT DIFFERENTIAL VOLTAGE (±mV)
45
Figure 24. DPI IEC 62132-4 Noise Immunity with 100 nF and Decoupling on
VDD2
Rev. 0 | Page 12 of 27
Data Sheet
ADM2795E
TEST CIRCUITS
VDD2
VOUT
A
|VOD|
VOC
14129-026
TxD
R
S2
CL
50pF
B
Figure 30. Driver Enable/Disable
375Ω
VTST
VOUT
RE
B
CL
375Ω
Figure 28. Driver Voltage Measurement over Common-Mode Voltage Range
14129-030
A
14129-027
60Ω
S1
DE
Figure 27. Driver Voltage Measurement
|VOD3|
RL
110Ω
14129-029
R
Figure 31. Receiver Propagation Delay
+1.5V
VDD1
RL
–1.5V
CL2
RE
14129-028
RLDIFF
B
S1
CL1
CL
VOUT
RE INPUT
Figure 32. Receiver Enable/Disable
Figure 29. Driver Propagation Delay
Rev. 0 | Page 13 of 27
S2
14129-031
A
ADM2795E
Data Sheet
SWITCHING CHARACTERISTICS
VDD1
VDD1
TxD
0.5VDD1
0V
DE
0.5VDD1
0V
tPHL
tPLH
0.5VDD1
0.5VDD1
tLZ
tZL
B
1/2 |VOD|
|VOD|
0.5VDD2
A, B
VOL + 0.5V
A
VOL
tSKEW = |tPLH – tPHL|
90% POINT
VOH
90% POINT
A, B
–VOUT
10% POINT
10% POINT
tR
tF
0.5VDD2
14129-032
VDIFF
VOH – 0.5V
0V
Figure 33. Driver Propagation Delay, Rise/Fall Timing
14129-034
+VOUT
tHZ
tZH
Figure 35. Driver Enable/Disable Timing
VDD1
RE
0.5VDD1
0.5VDD1
0V
0V
0V
tPLH
tPHL
VOL + 0.5V
OUTPUT LOW
0.5VDD1
tSKEW = |tPLH – tPHL|
VOL
tZH
14129-033
0.5VDD1
0.5VDD1
RxD
VOH
RxD
tLZ
tZL
Figure 34. Receiver Propagation Delay
RxD
VOL
tHZ
OUTPUT HIGH
0.5VDD1
VOH
VOH – 0.5V
0V
Figure 36. Receiver Enable/Disable Timing
Rev. 0 | Page 14 of 27
14129-035
A, B
Data Sheet
ADM2795E
THEORY OF OPERATION
RS-485 WITH ROBUSTNESS
The ADM2795E is a 3 V to 5.5 V RS-485/RS-422 transceiver
with robustness that reduces system failures when operating in
harsh application environments.
The ADM2795E is a RS-485/RS-422 transceiver that integrates
IEC 61000-4-5 Level 4 surge protection, allowing up to ±4 kV of
protection on the RS-485 bus pins without the need for external
protection components such as transient voltage suppressors
(TVS) or TISP® surge protectors. The ADM2795E has IEC
61000-4-4 Level 4 EFT protection up to ±2 kV and IEC 610004-2 Level 4 ESD protection on the bus pins.
The ADM2795E is an RS-485 transceiver that offers a defined
level of overvoltage fault protection in addition to IEC 61000-4-2
ESD, IEC 61000-4-4 EFT, and IEC 61000-4-5 surge protection
for the RS-485 bus pins.
INTEGRATED AND CERTIFIED IEC EMC SOLUTION
The driver outputs/receiver inputs of RS-485 devices often experience high voltage faults resulting from short circuits to power
supplies that exceed the −7 V to +12 V range specified in the
TIA/EIA-485-A standard. Typically, RS-485 applications require
costly external protection devices, such as positive temperature
coefficient (PTC) fuses, for operation in these harsh electrical
environments. In harsh electrical environments, system designers also must consider common EMC problems, choosing
components to provide IEC 61000-4-2 ESD, IEC 61000-4-4
EFT, and IEC 61000-4-5 surge protection for the RS-485 bus pins.
In choosing suitable EMC protection components, the system
designer is faced with two challenges: achieving compliance to
EMC regulations, and matching the dynamic breakdown
characteristics of the EMC protection to the RS-485 transceiver.
To overcome these challenges, the designer may need to run
multiple design, test, and printed circuit board (PCB) board
iterations, leading to a slower time to market and project budget
overruns.
To reduce system cost and design complexity, the ADM2795E
provides certified integrated EMC protection and overvoltage
fault protection on the RS-485 bus pins. The ADM2795E
integrated EMC and overvoltage fault protection circuits are
optimally performance matched, saving the circuit designer
significant design and testing time.
Figure 37 shows an isolated EMC protected RS-485 circuit
layout example, which targets IEC 61000-4-2 ESD Level 4,
IEC 61000-4-4 EFT Level 4, and IEC 61000-4-5 surge protection
to Level 4 for the RS-485 bus pins. This circuit uses several
discrete components, including two TISP surge protectors, two
transient blocking units (TBUs), and one dual TVS. Due to the
integrated protection components of the ADM2795E, the PCB
area is significantly reduced when compared to a solution with
discrete EMC protection components.
DIGITAL ISOLATOR
100nF
100nF
RS-485
TRANSCEIVER
TISP
100nF
TVS
TBU
TBU
TISP
100nF
100nF
100nF
14129-036
ADM2795E
Figure 37. ADM2795E Certified Integrated IEC 61000-4-5 Surge Solution, Saving the Designer Significant PCB Area
Rev. 0 | Page 15 of 27
ADM2795E
Data Sheet
OVERVOLTAGE FAULT PROTECTION
Table 11. Miswire Protection Table Abbreviations
The ADM2795E is an RS-485 transceiver that offers fault
protection over a 3 V to 5.5 V VDD2 operating range without the
need for close examination of the logic pin state (TxD input and
the DE and RE enable pins) of the RS-485 transceiver. The
transceiver is also fault protected over the entire extended
common-mode operating range of ±25 V.
Letter
H
L
X
The ADM2795E RS-485 driver outputs/receiver inputs are
protected from short circuits to any voltage within the range of
–42 V to +42 V ac/dc peak. The maximum short-circuit output
current in a fault condition is ±250 mA. The RS-485 driver
includes a foldback current limiting circuit that reduces the driver
current at voltages above the ±25 V common-mode range limit
of the transceiver (see Figure 21 in the Typical Performance
Characteristics section). This current reduction due to the
foldback feature allows better management of power dissipation
and heating effects.
VDD1
X
X
X
X
Table 12. High Voltage Miswire Protection
Supply
1
2
RxD
Miswire Protection at
RS-485 Outputs Pins1, 2
−42 V dc ≤ VA ≤ +42 V dc
−42 V dc ≤ VB ≤ +42 V dc
−42 V ac ≤ VA ≤ +42 V ac
−42 V ac ≤ VB ≤ +42 V ac
This is the ac/dc peak miswire voltage between Pin A and GND2, or Pin B and
GND2, or between Pin A and Pin B.
VA refers to the voltage on Pin A, and VB refers to the voltage on Pin B.
For a high voltage miswire on the RS-485 A and B bus pins with
biasing and termination resistors installed, there is a current
path through the biasing network to the ADM2795E power
supply pin, VDD2. To protect the ADM2795E in this scenario, the
device has an integrated VDD2 protection circuit.
The ADM2795E is protected against high voltage miswire
events when it operates on a bus that does not have RS-485
termination or bus biasing resistors installed. A typical miswire
event is where a high voltage 24 V ac/dc power supply is connected
directly to RS-485 bus pin connectors. The ADM2795E can
withstand miswiring faults of up to ±42 V peak on the RS-485
bus pins with respect to GND2 without damage. Miswiring
protection is guaranteed on the ADM2795E RS-485 A and B
bus pins, and is guaranteed in the case of a hot swap of
connectors to the bus pins. Table 11 and Table 12 provide a
summary of the high voltage miswire protection offered by the
ADM2795E. The ADM2795E is tested with ±42 V dc and with
±24 V ± 20% rms, 50 Hz/60 Hz, with both a hot plug and dc
ramp test waveforms. The test is performed in both powered
and unpowered/floating power supply cases, and at a range of
different states for the RS-485 TxD input and the DE and RE
enable pins. The RS-485 bus pins survive a high voltage miswire
from Pin A to GND2, from Pin B to GND2, and between Pin A
and Pin B.
DIGITAL ISOLATOR
VDD2
X
X
X
X
Inputs
DE RE
TxD
H/L H/L H/L
H/L H/L H/L
H/L H/L H/L
H/L H/L H/L
RS-485 NETWORK BIASING AND TERMINATION
±42 V MISWIRE PROTECTION
VDD1
Description
High level for logic pin
Low level for logic pin
On or off power supply state
The ADM2795E is a fault protected RS-485 device that also
features protection for its power supply pin. This means that the
current path through the R1 pull-up resistor does not cause
damage to the VDD2 pin, although the pull-up resistor itself can
be damaged if not appropriately power rated (see Figure 38).
The R1 pull-up resistor power rating depends on the miswire
voltage and the resistance value.
If there is a miswire between the A and B pins in the Figure 38
bus setup, the ADM2795E is protected, but the RT bus termination resistor can be damaged if not appropriately power rated.
The RT termination resistor power rating depends on the miswire
voltage and the resistance value.
VDD2
RS-485
TRANSCEIVER
ADM2795E
VDD2
R
R1
390Ω
RE
EMC
TRANSIENT
PROTECTION
CIRCUIT
DE
A
B
RT
220Ω
A
B
R2
390Ω
GND1
ISOLATION
BARRIER
GND2
14129-037
D
TxD
Figure 38. High Voltage Miswiring Protection for the ADM2795E with Bus Termination and Biasing Resistor
Rev. 0 | Page 16 of 27
Data Sheet
ADM2795E
IEC ESD, EFT, AND SURGE PROTECTION
humidity, temperature, barometric pressure, distance, and rate
of approach to the unit under test. This method is a better
representation of an actual ESD event but is not as repeatable.
Therefore, contact discharge is the preferred test method.
Electrical and electronic equipment must be designed to meet
system level IEC standards. The following are example system
level IEC standards:
•
•
•
During testing, the data port is subjected to at least 10 positive
and 10 negative single discharges with a minimum 1 sec interval
between each pulse. Selection of the test voltage is dependent on
the system end environment.
Process control and automation: IEC 61131-2
Motor control: IEC 61800-3
Building automation: IEC 60730-1
For data communication lines, these system level standards
specify varying levels of protection against the following three
types of high voltage transients:
•
•
•
Figure 39 shows the 8 kV contact discharge current waveform
as described in the IEC 61000-4-2 specification. Some of the
key waveform parameters are rise times of less than 1 ns and
pulse widths of approximately 60 ns.
IEC 61000-4-2 ESD
IEC 61000-4-4 EFT
IEC 61000-4-5 surge
IPEAK
30A
90%
Each of these specifications defines a test method to assess the
immunity of electronic and electrical equipment against the
defined phenomenon. The following sections summarize each
of these tests. The ADM2795E is fully tested in accordance with
these IEC EMC specifications, and is certified IEC EMC
compliant.
I30ns 16A
I60ns
8A
Electrostatic Discharge (ESD)
VDD1
DIGITAL ISOLATOR
RxD
60ns
30ns
Figure 39. IEC 61000-4-2 ESD Waveform (8 kV)
Figure 40 shows an example test setup where the ADM2795E
evaluation board was tested to both contact discharge and air
discharge for the IEC 61000-4-2 ESD standard.
Testing was performed with the IEC ESD gun connected to the
local bus, GND2. In testing to GND2, the ADM2795E is robust
to IEC 61000-4-2 events and passes the highest level recognized
in the standard, Level 4, which defines a contact discharge
voltage of ±8 kV and an air discharge voltage of ±15 kV.
VDD2
RS-485
TRANSCEIVER
ADM2795E
R
RE
EMC
TRANSIENT
PROTECTION
CIRCUIT
DE
A
IEC ESD
GUN
B
D
GND1
ISOLATION
BARRIER
GND2
14129-040
TxD
TIME
tR = 0.7ns TO 1ns
14129-038
10%
ESD is the sudden transfer of electrostatic charge between bodies
at different potentials caused by near contact or induced by an
electric field. ESD has the characteristics of high current in a
short time period. The primary purpose of the IEC 61000-4-2
test is to determine the immunity of systems to external ESD
events outside the system during operation. IEC 61000-4-2
describes testing using two coupling methods: contact discharge
and air gap discharge. Contact discharge implies a direct contact
between the discharge gun and the unit under test. During air
discharge testing, the charged electrode of the discharge gun is
moved toward the unit under test until a discharge occurs as an
arc across the air gap. The discharge gun does not make direct
contact with the unit under test. A number of factors affect the
results and repeatability of the air discharge test, including
Figure 40. IEC 61000-4-2 ESD Testing to GND1 or GND2
Rev. 0 | Page 17 of 27
ADM2795E
Data Sheet
in IEC 61000-4-4 attempts to simulate the interference resulting
from these types of events.
Testing was also performed with the IEC ESD gun connected to
the logic side GND1. Testing to GND1 demonstrates the
robustness of the ADM2795E isolation barrier. The isolation
barrier is capable of withstanding IEC 61000-4-2 ESD to ±9 kV
contact and to ±8 kV air. Testing was performed in normal
transceiver operation, with the ADM2795E clocking data at
2.5 Mbps. Table 13 and Table 16 summarize the certified test
results.
Figure 42 shows the EFT 50 Ω load waveforms. The EFT
waveform is described in terms of a voltage across a 50 Ω
impedance from a generator with a 50 Ω output impedance. The
output waveform consists of a 15 ms burst of 5 kHz high voltage
transients repeated at 300 ms intervals. The EFT test is also
performed with a 750 μs burst at a higher 100 kHz frequency.
Each individual pulse has a rise time of 5 ns and a pulse duration
of 50 ns, measured between the 50% point on the rising and falling
edges of the waveform. The total energy in a single EFT pulse is
similar to that in an ESD pulse.
Table 13. IEC 61000-4-2 Certified Test Results
ESD Gun
Connected to
GND2
IEC 61000-4-2 Test Result
±15 kV (air), ±8 kV (contact),
Level 4 protection
Withstands ±8 kV (air), ±9 kV
(contact)
GND1
Certified
Result
Yes
VPEAK
100%
Yes
90%
Figure 41 shows the 8 kV contact discharge current waveform
from the IEC 61000-4-2 standard compared to the HBM ESD
8 kV waveform. Figure 41 shows that the two standards each
specify a very different waveform shape and peak current. The
peak current associated with a IEC 61000-4-2 8 kV pulse is
30 A, while the corresponding peak current for HBM ESD is
more than five times less, at 5.33 A. The other difference is the
rise time of the initial voltage spike, with IEC 61000-4-2 ESD
having a much faster rise time of 1 ns, compared to the 10 ns
associated with the HBM ESD waveform. The amount of power
associated with an IEC ESD waveform is much greater than that
of an HBM ESD waveform. The ADM2795E with IEC 61000-4-2
ESD ratings is better suited for operation in harsh environments
compared to other RS-485 transceivers that state varying levels of
HBM ESD protection.
tR = 5ns ± 30%
tD = 5ns ± 30%
SINGLE
PULSE
50%
tD
tR
10%
TIME (ns)
15ms
BURST
OF PULSES
TIME (ms)
IPEAK
VPEAK
30A
90%
300ms
IEC 61000-4-2 ESD 8kV
I30ns
16A
TIME (ms)
14129-041
REPETITIVE
BURSTS
Figure 42. IEC 61000-4-4 EFT 50 Ω Load Waveforms
8A
5.33A
HBM ESD 8kV
10%
10ns
30ns
60ns
TIME
tR = 0.7ns TO 1ns
14129-039
I60ns
Figure 41. IEC 61000-4-2 ESD Waveform (8 kV) Compared to HBM ESD
Waveform (8 kV)
Electrical Fast Transients (EFTs)
EFT testing involves coupling a number of extremely fast transient
impulses onto the signal lines to represent transient disturbances
(associated with external switching circuits that are capacitively
coupled onto the communication ports), which may include
relay and switch contact bounce or transients originating from
the switching of inductive or capacitive loads—all of which are
very common in industrial environments. The EFT test defined
During testing, these EFT fast burst transients are coupled onto
the communication lines using a capacitive clamp, as shown in
Figure 43. The EFT is capacitively coupled onto the communication lines by the clamp rather than direct contact. This clamp
also reduces the loading caused by the low output impedance of
the EFT generator. The coupling capacitance between the clamp
and cable depends on cable diameter, shielding, and insulation
on the cable. The EFT clamp edge is placed 50 cm from the
equipment under test (EUT) (ADM2795E evaluation board).
The EFT generator is set up for either 5 kHz or 100 kHz repetitive EFT bursts. The ADM2795E was tested in both 5 kHz and
100 kHz test setups.
With the EFT clamp connected to GND2, the ADM2795E is
robust to IEC 61000-4-4 EFT transients and protects against the
highest level recognized in the standard, Level 4, which defines
Rev. 0 | Page 18 of 27
Data Sheet
ADM2795E
defines waveforms, test methods, and test levels for evaluating
immunity against these destructive surges.
a voltage level of ±2 kV. With the IEC 61000-4-4 EFT clamp connected to GND1, the ADM2795E is robust to IEC 61000-4-4
EFT transients and withstands up to ±2 kV. Testing was performed
in normal transceiver operation, with the ADM2795E clocking
data at 2.5 Mbps. The results shown in Table 14 are valid for a
setup with or without an RS-485 cable shield connection to
GND2. The ADM2795E withstands up to ±2 kV IEC 61000-4-4
EFT without damage. Table 14 and Table 16 summarize the
certified test results.
The waveforms are specified as the outputs of a waveform generator in terms of open circuit voltage and short-circuit current.
Two waveforms are described. The 10 µs/700 μs combination
waveform is used to test ports intended for connection to symmetrical communication lines: for example, telephone exchange lines.
The 1.2 µs/50 μs combination waveform generator is used in all
other cases, in particular short distance signal connections. For
RS-485 ports, the 1.2 µs/50 μs waveform is predominantly used
and is described in this section. The waveform generator has an
effective output impedance of 2 Ω; therefore, the surge transient
has high currents associated with it.
Table 14. IEC 61000-4-4 Certified Test Results
Certified
Result
Yes
Yes
IEC 61000-4-4 Test Result
±2 kV Level 4 protection
Withstands ±2 kV
Figure 44 shows the 1.2 µs and 50 μs surge transient waveform.
ESD and EFT have similar rise times, pulse widths, and energy
levels; however, the surge pulse has a rise time of 1.25 μs and the
pulse width is 50 μs. Additionally, the surge pulse energy is
three to four orders of magnitude larger than the energy in an
ESD or EFT pulse. Therefore, the surge transient is considered
the most severe of the EMC transients.
Surge
Surge transients are caused by overvoltage from switching or
lightning transients. Switching transients can result from power
system switching, load changes in power distribution systems,
or various system faults such as short circuits. Lightning
transients can be a result of high currents and voltages injected
into the circuit from nearby lightning strikes. IEC 61000-4-5
VDD2
VDD1
RS-485
TRANSCEIVER
DIGITAL ISOLATOR
RxD
IEC EFT
GENERATOR
5kHz, 100kHz
ADM2795E
R
RE
EMC
TRANSIENT
PROTECTION
CIRCUIT
DE
A
RS-485
CABLE
B
IEC EFT
CLAMP
D
TxD
GND1
GND2
RS-485 CABLE SHIELD
14129-042
ISOLATION
BARRIER
Figure 43. IEC 61000-4-4 EFT Testing to GND1 or GND2
VPEAK
100%
90%
50%
t2
t1 = 1.2µs ± 30%
t2 = 50µs ± 20%
10%
t1
30% MAX
Figure 44. IEC 61000-4-5 Surge 1.2 µs/50 μs Waveform
Rev. 0 | Page 19 of 27
TIME (µs)
14129-043
EFT Clamp
Connected to
GND2
GND1
ADM2795E
Data Sheet
VDD1
VDD2
DIGITAL ISOLATOR
RxD
RS-485
TRANSCEIVER
ADM2795E
R
COUPLING NETWORK
RE
EMC
TRANSIENT
PROTECTION
CIRCUIT
DE
80Ω
A
B
IEC SURGE
GENERATOR
CD
80Ω
D
GND1
ISOLATION
BARRIER
GND2
14129-044
TxD
Figure 45. IEC 61000-4-5 Surge Testing to GND1 or GND2
IEC 61000-4-5 surge testing involves using a coupling/decoupling
network (CDN) to couple the surge transient into the RS-485 A
and B bus pins. The coupling network for a half-duplex RS-485
device consists of an 80 Ω resistor on both the A and B lines
and a coupling device. The total parallel sum of the resistance is
40 Ω. The coupling device can be capacitors, gas arrestors, clamping devices, or any method that allows the EUT to function
correctly during the applied test. During the surge test, five
positive and five negative pulses are applied to the data ports
with a maximum time interval of one minute between each pulse.
The standard states that the device must be set up in normal
operating conditions for the duration of the test. Figure 45
shows the test setup for surge testing. Testing was performed in
normal transceiver operation, with the ADM2795E clocking
data at 2.5 Mbps.
up to ±4 kV surge. The ADM2795E withstands up to ±4 kV IEC
61000-4-5 surge without damage and with no bit errors in data
communications. Testing to GND1 demonstrates the robustness
of the ADM2795E isolation barrier. Table 15 and Table 16
summarize the certified test results.
With the IEC surge generator connected to GND2, the
ADM2795E is robust to IEC 61000-4-5 events and protects
against the highest level recognized in the standard, Level 4,
which defines a peak voltage of ±4 kV.
•
•
•
•
With the IEC surge generator connected to GND1, the
ADM2795E is robust to IEC 61000-4-5 events and withstands
Table 15. IEC 61000-4-5 Certified Test Results
Surge Generator
Connected to
GND2
GND1
IEC 61000-4-5 Test
Result
±4 kV Level 4 protection
Withstands ±4 kV
Certified
Result
Yes
Yes
Table 16 summarizes the ADM2795E performance and
classification achieved for the noted IEC system level EMC
standards.
The performance corresponds to each classification as follows:
Class A—normal operation
Class B—temporary loss of performance (bit errors)
Class C—system needs reset
Class D—permanent loss of function
Table 16. Summary of Certified EMC System Level Classifications for the ADM2795E
Test
IEC 61000-4-5 Surge
IEC 61000-4-4 Electrical Fast Transient (EFT)
IEC 61000-4-2 Electrostatic Discharge (ESD)
IEC 61000-4-6 Conducted RF Immunity
IEC 61000-4-3 Radiated RF Immunity
IEC 61000-4-8 Magnetic Immunity
Ground Connection
GND1
GND2
GND1
GND2
GND1
GND2
GND1
GND2
GND2
GND2
Rev. 0 | Page 20 of 27
Classification
Class A
Class B
Class B
Class B
Class B
Class B
Class A
Class A
Class A
Class A
Highest Pass Level
±4 kV
±4 kV
±2 kV
±2 kV
±8 kV (air), ±9 kV (contact)
±15 kV (air), ±8 kV (contact)
10 V/m rms
10 V/m rms
30 V/m
100 A/m
Data Sheet
ADM2795E
IEC CONDUCTED, RADIATED, AND MAGNETIC
IMMUNITY
Table 17. IEC 61000-4-6 EUT and Equipment
Parameter
IEC 61000-4-6
Clamp
IEC 61000-4-6 Test
Level
IEC 61000-4-6 Conducted RF Immunity
The IEC 61000-4-6 conducted immunity test is applicable to
products that operate in environments where RF fields are
present and that are connected to mains supplies or other
networks (signal or control lines). The source of conducted
disturbances are electromagnetic fields, emanating from RF
transmitters that may act on the whole length of cables
connected to installed equipment.
EUT
EUT Data Rate
EUT Power
Cable Between EUT
In the IEC 61000-4-6 test, an RF voltage is swept/stepped from
150 kHz to 80 MHz or 100 MHz. The RF voltage is amplitude
modulated 80% at 1 kHz. One ADM2795E evaluation board
was tested to Level 3, which is the highest test level of 10 V. For
IEC 61000-4-6 testing, the stress signal is applied by using the
clamp detailed in Table 17. The clamp is placed on the communications cable between two ADM2795E transceivers. For all testing,
the equipment and EUT setup are as described in Table 17 and
Figure 46.
Cable Termination
Pass/Fail Criteria
Details
Schaffner KEMZ 801, placed at 30 cm
from the EUT
Level 3, 0.15 MHz to 80 MHz, 10 V/m rms,
80% amplitude modulated (AM) by a
1 kHz sinusoidal
EVAL-ADM2795EEBZ
2.5 Mbps
9 V battery at VDD1 and VDD2, regulated on
EUT to 5 V
5 m, Unitronic® Profibus, 22 American
wire gauge (AWG )
120 Ω resistor at both cable ends
Pass: data at receiver with a pulse width
distortion within 10% of mean
Table 18. IEC 61000-4-6 Certified Test Results
Clamp
Location
from EUT
(cm)
30
30
30
30
Table 17 shows the test results where the EUT passed IEC
61000-4-6 to Level 3. For all of the tests, the IEC 61000-4-6
clamp was placed at the EVAL-ADM2795EEBZ EUT, and the
cable shield was either floating or Earth grounded. The second
EVAL-ADM2795EEBZ (auxiliary equipment) was placed on the
network to terminate the communications bus. The IEC 61000-4-6
generator clamp was either connected to GND1 or GND2 of the
ADM2795E EUT to provide a return current path for the IEC
61000-4-6 transient current.
Cable
Shield
Floating
Earthed
Floating
Earthed
Current
Return
Path
GND1
GND1
GND2
GND2
IEC 61000-4-6
Test
Frequency
(MHz)
0.15 to 80
0.15 to 80
0.15 to 80
0.15 to 80
Certified
Result
Pass
Pass
Pass
Pass
The ADM2795E evaluation board is tested and certified to pass
IEC 61000-4-6 conducted RF immunity testing to Level 3 at
10 V/m rms, in a variety of configurations as described in
Table 16 and Table 17.
VDD1
DIGITAL ISOLATOR
VDD2
VDD2
RS-485
TRANSCEIVER
ADM2795E
EUT
RxD
R
RE
EMC
TRANSIENT
PROTECTION
CIRCUIT
DE
A
A
B
IEC
61000-4-6
CLAMP
ISOLATION
BARRIER
GND2
RS-485 CABLE SHIELD
B
DIGITAL ISOLATOR
RxD
R
RE
EMC
TRANSIENT
PROTECTION
CIRCUIT
DE
D
GND2
TxD
GND1
14129-046
GND1
RS-485
TRANSCEIVER
AUXILIARY
EQUIPMENT
RT
D
TxD
ADM2795E
IEC
61000-4-6
GENERATOR
VDD1
Figure 46. IEC 61000-4-6 Conducted RF Immunity Example Test Setup Testing to GND1 or GND2
Rev. 0 | Page 21 of 27
ADM2795E
Data Sheet
IEC 61000-4-3 Radiated RF Immunity
IEC 61000-4-8 Magnetic Immunity
Testing to IEC 61000-4-3 ensures that electronic equipment is
immune to commonly occurring radiated RF fields. Some
commonly occurring unintentional RF emitting devices in an
industrial application are electric motors and welders.
Testing to IEC 61000-4-8 ensures that electronic equipment is
immune to commonly occurring magnetic fields. The source of
magnetic fields in typical industrial communication applications is
power line current or 50 Hz/60 Hz transformers in close proximity
to the equipment.
In the IEC 61000-4-3 test, a radiated RF field is generated by an
antenna in a shielded anechoic chamber using a precalibrated
field, swept from 80 MHz to 2.7 GHz. The RF voltage is
amplitude modulated 80% at 1 kHz. Each face of the EUT is
subjected to vertical and horizontal polarizations.
In the IEC 61000-4-8 test, a controlled magnetic field of defined
field strength is produced by driving a large coil (induction coil)
with a test current generator. The EUT is placed at the center of
the induction coil, subjecting the EUT to a magnetic field.
Figure 47 shows the test setup with the EVAL-ADM2795EEBZ,
the EUT, placed in an anechoic chamber, powered with two 9 V
batteries. The EVAL-ADM2795EEBZ on board regulators
power VDD1 at 5.0 V and VDD2 at 5.0 V. The EVAL-ADM2795EEBZ
is loaded with a 120 Ω termination resistor for the duration of
the test. A pattern generator provides a 2.5 Mbps data input to
the ADM2795E TxD pin. The ADM2795E receiver output
(RxD) is monitored with an oscilloscope.
Figure 48 shows the test setup with the EVAL-ADM2795EEBZ,
the EUT, placed in an anechoic chamber, powered with two 9 V
batteries. The EVAL-ADM2795EEBZ on board regulators power
VDD1 at 5.0 V and VDD2 at 5.0 V. The EVAL-ADM2795EEBZ is
loaded with a 120 Ω termination resistor for the duration of the
test. A pattern generator provides a 2.5 Mbps data input to the
ADM2795E TxD pin. The ADM2795E receiver output (RxD) is
monitored with an oscilloscope.
The pass criteria chosen is less than a 10% change in the bit
width of the RxD signal in the presence of the IEC 61000-4-3
radiated RF field.
The pass criteria chosen is less than a 10% change in the bit
width of the RxD signal in the presence of the IEC 61000-4-8
magnetic field.
The ADM2795E evaluation board is tested and certified to pass
IEC 61000-4-3 radiated RF immunity testing to Level 4 (30 V/m).
Level 4 is the highest level specified in the IEC 61000-4-3
standard.
The ADM2795E evaluation board is tested and certified to pass
IEC 61000-4-8 magnetic immunity testing to Level 5 (100 A/m).
Level 5 is the highest level specified in the IEC 61000-4-8
standard.
EUT
TESTED ON ALL FOUR SIDES
ANECHOIC
CHAMBER
RF ABSORBING
MATERIAL
EUT
INDUCTION LOOP
EVAL-ADM2795EEBZ
VDD1
9V
BATTERY
VDD2
9V
BATTERY
VDD1
9V
BATTERY
TRANSMIT
ANTENNA
VDD2
9V
BATTERY
EVAL-ADM2795EEBZ
IEC 61000-4-8
TEST CURRENT
GENERATOR
EUT
EUT
ISOLATION
BARRIER
ANTENNA AT
1 METER TO 3 METERS
FROM EUT
ISOLATION
BARRIER
POWER MONITOR
AND AMPLIFIER
14129-148
PATTERN GENERATOR
TxD DRIVER INPUT
Figure 47. Testing for IEC 61000-4-3 Radiated RF Immunity
PATTERN GENERATOR
TxD DRIVER INPUT
Figure 48. Testing for IEC 61000-4-8 Magnetic Immunity
Rev. 0 | Page 22 of 27
14129-149
OSCILLOSCOPE MONITORING
RxD RECEIVER OUTPUT
OSCILLOSCOPE MONITORING
RxD RECEIVER OUTPUT
Data Sheet
ADM2795E
APPLICATIONS INFORMATION
RADIATED EMISSIONS AND PCB LAYOUT
The ADM2795E meets stringent electromagnetic interference
(EMI) emissions targets (EN55022 Class B) with minimal PCB
layout considerations. To achieve a 6 dBµV/m margin from
EN55022 Class B limits, add a 120 pF, 0603 body size capacitor
on the PCB trace connected to the RxD pin and GND1 (see
Figure 49). Place the capacitor at 5 mm from the RxD pin for
optimal performance. The ADM2795E evaluation board user
guide provides an example PCB layout. Figure 18 shows a typical
performance plot of the ADM2795E EN55022 radiated emissions
profile (with a 120 pF capacitor to GND1 on the RxD pin).The
effect of adding load capacitance on the RxD pin is shown in
the typical waveform rise and fall times in Figure 26.
NOISE IMMUNITY
Direct power injection (DPI) measures the ability of a
component to reject noise injected onto the power supply or
input pins. The ADM2795E was tested to the DPI IEC 62132-4
standard, with a high power noise source capacitively coupled
into either the VDD1 or VDD2 power supply pin. The noise source
was swept through a 300 kHz to 1 GHz frequency band. During
DPI IEC 62132-4 testing, the ADM2795E TxD pin was clocked
at 2.5 Mbps, and the clock data output on the RxD pin was
monitored for errors (loopback test mode). The fail criteria was
defined as greater than ±10% change in the bit width of the
RxD signal.
Figure 50 shows a test setup, with the DPI noise source injected
through a 6.8 nF capacitor on the ADM2795E VDD1 power
supply pin. Figure 22 to Figure 24 in the Typical Performance
Characteristics section show the fail point for the ADM2795E
across the noise power (dBm) vs. DPI frequency (Hz). Figure 21
shows that the addition of a 10 µF decoupling capacitor, in
addition to the standard 100 nF decoupling capacitor, improves
low frequency noise immunity.
Performance to the IEC 62132-4 standard was evaluated for the
ADM2795E and compared to other isolators/transceivers
available in the market. The ADM2795E noise immunity
performance exceeds that of other similar products. The
ADM2795E maintains excellent performance over frequency,
but other isolation products exhibit bit errors in the 200 MHz to
700 MHz frequency band.
FULLY RS-485 COMPLIANT OVER AN EXTENDED
±25 V COMMON-MODE VOLTAGE RANGE
The ADM2795E is an RS-485 transceiver that offers an extended
common-mode input range of ±25 V across an operating voltage
range of 3 V to 5.5 V, while still meeting or exceeding compliance
with TIA/EIA RS-485/RS-422 standards, which specify a bus
differential voltage of at least 1.5 V across the common-mode
voltage range. In addition, when powered at greater than 4.5 V
VDD2, the ADM2795E driver output is a minimum 2.1 V |VOD|,
meeting the requirements for a Profibus compliant RS-485
driver. The extended common-mode input voltage range of
±25 V improves system robustness over long cable lengths, where
large differences in ground potential between RS-485 transceivers
are possible. The extended common-mode input voltage range
of ±25 V improves data communication reliability in noisy
environments over long cable lengths where ground loop
voltages are possible.
1.7 V TO 5.5 V VDD1 LOGIC SUPPLY
The ADM2795E features a logic supply pin, VDD1, for flexible
digital interface operational to voltages as low as 1.7 V. The
VDD1 pin powers the logic inputs (TxD input, and DE and RE
control pins) and the RxD output. These pins interface with
logic devices such as universal asynchronous receiver/transmitters
(UARTs), application specific integrated circuits (ASICs), and
microcontrollers. Many of these devices use power supplies
significantly lower than 5 V.
100nF
100nF
VDD1
VDD2
GND1
GND2
TxD
DE
RE
V
100nF DD2
GND2
A
NIC
GND2
GND1
GND2
Figure 49. Recommended PCB Layout to Meet EN55022 Class B Radiated Emissions
Rev. 0 | Page 23 of 27
14129-045
RxD
120pF
B
ADM2795E
ADM2795E
Data Sheet
DPI
NOISE SOURCE
INJECTION
TWO FERRITES
BLMBD102SN1
VDD1
5V
220µH
6.8nF
VDD2
VDD1
C2
100nF
C1
10µF
100nF
GND1
MINIMUM 400Ω IMPEDANCE
ACROSS 300kHz TO 1GHz RANGE
VDD2
5V
ADM2795E
2.5Mbps
CLOCK
TxD
A RS-485A
RxD
B
60Ω
14129-047
RS-485B
NOTES
1. SIMPLIFIED DIAGRAM, ALL PINS NOT SHOWN.
Figure 50. Typical Setup for DPI IEC 62132-4 Noise Immunity Test
TRUTH TABLES
RECEIVER FAIL-SAFE
Table 20 and Table 21 use the abbreviations shown in Table 19.
VDD1 supplies the DE, TxD, RE, and RxD pins only.
The receiver input includes a fail-safe feature that guarantees a
logic high RxD output when the A and B inputs are floating,
open circuit, or short circuit. A logic high RxD output is guaranteed in a terminated transmission line with all drivers disabled.
This fail-safe RxD guaranteed output logic high is implemented
by setting the receiver input threshold between −30 mV and
−200 mV. If the differential receiver input voltage (A − B) is
greater than or equal to −30 mV, RxD is logic high. If A − B is
less than or equal to −200 mV, RxD is logic low. In the case of a
terminated bus with all transmitters disabled, the receiver
differential input voltage is pulled to 0 V by the termination.
With the receiver thresholds of the ADM2795E, this results in a
RxD output logic high with a 30 mV minimum noise margin.
Table 19. Truth Table Abbreviations
Letter
H
I
L
X
Z
NC
Description
High level
Indeterminate
Low level
Any state
High impedance (off )
Disconnected
Table 20. Transmitting Truth Table
VDD2
On
On
On
On
On
On
Off
Off
Supply Status
VDD1
On
On
On
Off
Off
Off
On
Off
DE
H
H
L
H
H
L
X
X
Inputs
TxD
H
L
X
H
L
X
X
X
A
H
L
Z
I
I
I
Z
Z
Outputs
B
L
H
Z
I
I
I
Z
Z
Table 21. Receiving Truth Table
Supply Status
VDD2
On
On
On
On
On
On
On
On
On
On
Off
Off
VDD1
On
On
Off
Off
On
Off
On
Off
On
Off
Off
Off
Inputs
A−B
>−0.03 V
<−0.2 V
>−0.03 V
<−0.2 V
−0.2 V < A − B < −0.03 V
−0.2 V < A − B < −0.03 V
Inputs open/shorted
Inputs open/shorted
X
X
X
X
Outputs
RE
L
L
L
L
L
L
L
L
H
H
H
L or NC
RxD
H
L
I
I
I
I
H
I
Z
I
I
I
RS-485 DATA RATE AND BUS CAPACITANCE
The data rate and bus node capability of the ADM2795E are
dependent on the operating temperature of the device. As the
operating temperature of the ADM2795E is increased, the capacitance of the ADM2795E integrated EMC protection circuitry is
also increased. The driver output structures of the ADM2795E
can be simplified as low-pass filter structures, with a given
resistance and capacitance. As the operating temperature increases,
the capacitance increases. The low-pass filter effectively works
to decrease the maximum data rate that can be driven on the
RS-485 bus pins.
INSULATION WEAR OUT
The lifetime of insulation caused by wear out is determined by
its thickness, material properties, and the voltage stress applied.
It is important to verify that the product lifetime is adequate at
the application working voltage. The working voltage supported
by an isolator for wear out may not be the same as the working
voltage supported for tracking. The working voltage applicable
to tracking is specified in most standards.
Testing and modeling show that the primary driver of longterm degradation is displacement current in the polyimide
insulation causing incremental damage. The stress on the insulation can be broken down into broad categories, such as dc
stress, which causes very little wear out because there is no
Rev. 0 | Page 24 of 27
Data Sheet
ADM2795E
displacement current, and an ac component time varying
voltage stress, which causes wear out.
The ratings in certification documents are typically based on
60 Hz sinusoidal stress because this reflects isolation from the
line voltage. However, many practical applications have
combinations of 60 Hz ac and dc across the barrier as shown in
Equation 1. Because only the ac portion of the stress causes
wear out, the equation can be rearranged to solve for the ac rms
voltage, as shown in Equation 2. For insulation wear out with the
polyimide materials used in the ADM2795E, the ac rms voltage
determines the product lifetime.
VRMS = VAC RMS 2 + VDC 2
(1)
VAC RMS = VRMS 2 − VDC 2
(2)
or
where:
VRMS is the total rms working voltage.
VAC RMS is the time varying portion of the working voltage.
VDC is the dc offset of the working voltage.
VDC
TIME
Figure 51. Critical Voltage Example
The working voltage across the barrier from Equation 1 is
VRMS = VAC RMS 2 + VDC 2
VAC RMS = VRMS 2 − VDC 2
VAC RMS = 4662 − 4002
VAC RMS = 240 V rms
In this case, the ac rms voltage is simply the line voltage of
240 V rms. This calculation is more relevant when the
waveform is not sinusoidal. The value is compared to the limits
for working voltage in Table 8 for the expected lifetime, less
than a 60 Hz sine wave, and it is well within the limit for a
50-year service life.
HOT SWAP CAPABILITY
When a PCB is inserted into a hot (or powered) backplane,
differential disturbances to the data bus can lead to data errors.
The ADM2795E was lab tested to ensure that the RS-485 A and
B bus pins do not output spurious data during a power-up/powerdown event, which simulates a PCB hot insertion. The power
supply ramp test rates were 0 V to 5 V in 300 µs (fast ramp rate),
and 0 V to 5 V in 9.5 ms (slow ramp rate). For these ramp rates,
the RS-485 A and B outputs were monitored and no output
glitches were observed.
ROBUST HALF-DUPLEX RS-485 NETWORK
VAC RMS
14129-048
ISOLATION VOLTAGE
The following example frequently arises in power conversion
applications. Assume that the line voltage on one side of the
isolation is 240 V ac rms and a 400 V dc bus voltage is present
on the other side of the isolation barrier. The isolator material is
polyimide. To establish the critical voltages in determining the
creepage, clearance, and lifetime of a device, see Figure 51 and
the following equations.
VRMS
To determine if the lifetime is adequate, obtain the time varying
portion of the working voltage. To obtain the ac rms voltage,
use Equation 2.
Note that the dc working voltage limit in Table 8 is set by the
creepage of the package as specified in IEC 60664-1. This value
can differ for specific system level standards.
Calculation and Use of Parameters Example
VPEAK
This VRMS value is the working voltage used together with the
material group and pollution degree when looking up the
creepage required by a system standard.
Figure 52 shows a robust isolated RS-485 communications
network, with bus communications running over 1000 feet of
cabling. Over long cable runs with multiple RS-485 nodes, a
number of hazards can either corrupt data communication or
even cause permanent damage to the RS-485 interface. The
ADM2795E provides robust protection against high voltage
faults to bus power supplies and EMC transients, such as an
IEC 61000-4-5 surge. In addition, the ADM2795E has an
extended common-mode input range of ±25 V, which allows
±25 V of ground potential difference between the isolated
GND2 pins of two or more ADM2795E devices.
VRMS = 2402 + 4002
VRMS = 466 V
Rev. 0 | Page 25 of 27
ADM2795E
DIGITAL ISOLATOR
24V
POWER –
SUPPLY +
VDD2
RS-485
TRANSCEIVER
RxD
MISWIRE
TO A 24V
SUPPLY
VDD2
EMC
TRANSIENT
RS-485
TRANSCEIVER
ADM2795E
R
EMC
TRANSIENT
PROTECTION
CIRCUIT
DE
A
A
RT
B
B
ISOLATION
BARRIER
VDD1
DIGITAL ISOLATOR
RxD
RE
DE
D
VDD2
RS-485
TRANSCEIVER
RS-485
TRANSCEIVER
ADM2795E
VDD1
DIGITAL ISOLATOR
ADM2795E
RxD
R
EMC
TRANSIENT
PROTECTION
CIRCUIT
DE
A
A
B
B
RE
EMC
TRANSIENT
PROTECTION
CIRCUIT
DE
D
D
ISOLATION
BARRIER
GND1
V
VDD2
DD2
R
GND1
TxD
GND2
GND2
RE
TxD
RxD
EMC
TRANSIENT
PROTECTION
CIRCUIT
D
GND1
DIGITAL ISOLATOR
ADM2795E
R
RE
TxD
VDD1
GND2
COMMUINICATION
WITH ±25V
POTENTIAL DIFFERENCE
BETWEEN ISOLATED
BUS GROUNDS
GND2
Figure 52. Robust Half-Duplex Isolated RS-485 Communication Network
Rev. 0 | Page 26 of 27
TxD
GND1
14129-049
VDD1
Data Sheet
Data Sheet
ADM2795E
OUTLINE DIMENSIONS
10.50 (0.4134)
10.10 (0.3976)
9
16
7.60 (0.2992)
7.40 (0.2913)
8
1.27 (0.0500)
BSC
0.30 (0.0118)
0.10 (0.0039)
COPLANARITY
0.10
0.51 (0.0201)
0.31 (0.0122)
10.65 (0.4193)
10.00 (0.3937)
0.75 (0.0295)
45°
0.25 (0.0098)
2.65 (0.1043)
2.35 (0.0925)
SEATING
PLANE
8°
0°
0.33 (0.0130)
0.20 (0.0079)
1.27 (0.0500)
0.40 (0.0157)
COMPLIANT TO JEDEC STANDARDS MS-013-AA
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
03-27-2007-B
1
Figure 53. 16-Lead Standard Small Outline Package [SOIC_W]
Wide Body
(RW-16)
Dimensions shown in millimeters and (inches)
ORDERING GUIDE
Model1
ADM2795EBRWZ
ADM2795EBRWZ-RL7
ADM2795EARWZ
ADM2795EARWZ-RL7
EVAL-ADM2795EEBZ
1
Temperature
Range
−40°C to +125°C
−40°C to +125°C
−40°C to +85°C
−40°C to +85°C
Package Description
16-Lead Standard Small Outline Package [SOIC_W]
16-Lead Standard Small Outline Package [SOIC_W], 7” Reel
16-Lead Standard Small Outline Package [SOIC_W]
16-Lead Standard Small Outline Package [SOIC_W] , 7” Reel
Evaluation Board
Z = RoHS Compliant Part.
©2016 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D14129-0-10/16(0)
Rev. 0 | Page 27 of 27
Package
Option
RW-16
RW-16
RW-16
RW-16
Ordering
Quantity
400
400