Datasheet

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High Speed, ESD-Protected, Half-/Full-Duplex

iCoupler Isolated RS-485 Transceiver

Data Sheet

ADM2491E

Rev. C Document Feedback

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FEATURES

Isolated, RS-485/RS-422 transceiver, configurable as half- or

full-duplex

±8 kV ESD protection on RS-485 input/output pins

16 Mbps data rate

Complies with ANSI TIA/EIA RS-485-A-1998 and

ISO 8482: 1987(E)

Suitable for 5 V or 3.3 V operation (V

DD1

)

High common-mode transient immunity: >25 kV/μs

Receiver has open-circuit, fail-safe design

32 nodes on the bus

Thermal shutdown protection

Safety and regulatory approvals

UL recognition: 5000 V rms isolation voltage

for 1 minute, per UL 1577

VDE certificate of conformity

DIN V VDE V 0884-10 (VDE V 0884-10): 2006-12

Reinforced insulation, V

IORM

= 849 V peak

Operating temperature range: −40°C to +85°C

Wide body, 16-lead SOIC package

APPLICATIONS

Isolated RS-485/RS-422 interfaces

Industrial field networks

INTERBUS

Multipoint data transmission systems

FUNCTIONAL BLOCK DIAGRAM

DD1

GND

DD2

GND

TxD

RxD

ADM2491E

06985-001

GALVANIC ISOLATION

Figure 1.

GENERAL DESCRIPTION

The ADM2491E is an isolated data transceiver with ±8 kV ESD

protection and is suitable for high speed, half- or full-duplex

communication on multipoint transmission lines. For half-

duplex operation, the transmitter outputs and the receiver

inputs share the same transmission line. Transmitter output

Pin Y is linked externally to receiver input Pin A, and transmit-

ter output Pin Z is linked to receiver input Pin B.

The ADM2491E is designed for balanced transmission lines

and complies with ANSI TIA/EIA RS-485-A-1998 and ISO

8482: 1987(E). The device employs Analog Devices, Inc.,

iCoupler® technology to combine a 3-channel isolator, a three-

state differential line driver, and a differential input receiver into

a single package.

The differential transmitter outputs and receiver inputs feature

electrostatic discharge circuitry that provides protection to

±8 kV using the human body model (HBM). The logic side of

the device can be powered with either a 5 V or a 3.3 V supply,

whereas the bus side requires an isolated 5 V supply.

The device has current-limiting and thermal shutdown features

to protect against output short circuits and situations in which

bus contention could cause excessive power dissipation.

The ADM2491E is available in a wide body, 16-lead SOIC package

and operates over the −40°C to +85°C temperature range.

Summary of content (16 pages)

PAGE 1
High Speed, ESD-Protected, Half-/Full-Duplex iCoupler Isolated RS-485 Transceiver ADM2491E Data Sheet FEATURES FUNCTIONAL BLOCK DIAGRAM VDD1 VDD2 ADM2491E DE GALVANIC ISOLATION TxD Y Z A RxD B RE GND1 GND2 06985-001 Isolated, RS-485/RS-422 transceiver, configurable as half- or full-duplex ±8 kV ESD protection on RS-485 input/output pins 16 Mbps data rate Complies with ANSI TIA/EIA RS-485-A-1998 and ISO 8482: 1987(E) Suitable for 5 V or 3.
PAGE 2
ADM2491E Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Switching Characteristics .................................................................9 Applications ....................................................................................... 1 Typical Performance Characteristics ........................................... 10 Functional Block Diagram ..........................................................
PAGE 3
Data Sheet ADM2491E SPECIFICATIONS All voltages are relative to their respective ground; 3.0 V ≤ VDD1 ≤ 5.5 V, 4.5 V ≤ VDD2 ≤ 5.5 V. All minimum/maximum specifications apply over the entire recommended operation range, unless otherwise noted. All typical specifications are at TA = 25°C, VDD1 = VDD2 = 5.0 V, unless otherwise noted. Table 1.
PAGE 4
ADM2491E Data Sheet TIMING SPECIFICATIONS TA = −40°C to +85°C. Table 2.
PAGE 5
Data Sheet ADM2491E INSULATION AND SAFETY-RELATED SPECIFICATIONS Table 5. Parameter Rated Dielectric Insulation Voltage Minimum External Air Gap (Clearance) Symbol L(I01) Value 5000 7.7 Unit V rms mm min Minimum External Tracking (Creepage) L(I02) 8.1 mm min Minimum Internal Gap (Internal Clearance) Tracking Resistance (Comparative Tracking Index) Isolation Group CTI 0.
PAGE 6
ADM2491E Data Sheet ABSOLUTE MAXIMUM RATINGS TA = 25 °C, unless otherwise noted. Each voltage is relative to its respective ground. Table 7. Parameter Storage Temperature Ambient Operating Temperature VDD1 VDD2 Logic Input Voltages Bus Terminal Voltages Logic Output Voltages Average Output Current, per Pin ESD (Human Body Model) on A, B, Y, and Z Pins θJA Thermal Impedance Rating −55°C to +150°C −40°C to +85°C −0.5 V to +7 V −0.5 V to +6 V −0.5 V to VDD1 + 0.5 V −9 V to +14 V −0.5 V to VDD1 + 0.
PAGE 7
Data Sheet ADM2491E PIN CONFIGURATION AND FUNCTIONAL DESCRIPTIONS VDD1 1 16 VDD2 GND1 2 15 GND2 14 A RxD 3 TOP VIEW 13 B DE 5 (Not to Scale) 12 Z TxD 6 11 Y NC 7 10 NC GND1 8 9 GND2 NC = NO CONNECT 06985-002 RE 4 ADM2491E Figure 2. ADM2491E Pin Configuration Table 8. Pin Function Descriptions Pin No. 1 Mnemonic VDD1 2, 8 3 4 GND1 RxD RE 5 DE 6 7, 10 9, 15 11 12 13 14 16 TxD NC GND2 Y Z B A VDD2 Description Power Supply (Logic Side).
PAGE 8
ADM2491E Data Sheet TEST CIRCUITS RL 2 CL1 Y VOC Z Figure 3. Driver Voltage Measurement 06985-006 RLDIFF RL 2 06985-003 VOD CL2 Figure 6. Driver Propagation Delay 375Ω A VTEST 60Ω VOUT B Figure 7. Receiver Propagation Delay Figure 4. Driver Voltage Measurement VDD1 CL 06985-004 375Ω 06985-007 VOD VDD2 ADM2491E VCC VOUT Y RL S1 0V OR 3V DE S2 Z RTERMINATION Figure 8. Driver Enable/Disable A RxD +1.5V B –1.
PAGE 9
Data Sheet ADM2491E SWITCHING CHARACTERISTICS VDD1 TxD 1.5V 1.5V 0V tPLH A, B tPHL 0V 0V tPLH tPHL Z 1/2VOUT VOUT Y VOH tPWD = |tPLH – tPHL| 1.5V 90% POINT 1.5V Y, Z 10% POINT tR tF VOL 06985-010 10% POINT Figure 10. Driver Propagation Delay, Rise/Fall Timing Figure 12. Receiver Propagation Delay VDD1 DE 0.5VDD1 VDD1 RE 0.5VDD1 0.5VDD1 0.5VDD1 0V tZL 2.3V Y, Z 0V tZL tLZ tLZ 1.5V RxD VOL + 0.5V tZH tZH tHZ OUTPUT HIGH VOH Y, Z 2.3V VOH – 0.5V 0V VOL + 0.
PAGE 10
ADM2491E Data Sheet TYPICAL PERFORMANCE CHARACTERISTICS 60 2.58 NO LOAD 50 2.54 tPLH tPHL 40 2.52 DELAY (ns) 100Ω LOAD 2.50 2.48 30 54Ω LOAD 20 2.46 10 2.44 –20 0 20 40 60 80 TEMPERATURE (°C) 0 –40 06985-014 2.42 –40 –20 0 20 40 60 06985-035 IDD1 SUPPLY CURRENT (mA) 2.56 80 TEMPERATURE (°C) Figure 17. Receiver Propagation Delay vs. Temperature Figure 14. IDD1 Supply Current vs. Temperature 60 ∆: 2.12V @: 7.
PAGE 11
Data Sheet ADM2491E 350 4.76 4.74 4.73 250 SIDE 2 VOLTAGE (V) SAFETY-LIMITING CURRENT (mA) 4.75 300 200 150 SIDE 1 100 4.72 4.71 4.70 4.69 4.68 4.67 50 100 150 CASE TEMPERATURE (°C) 200 4.65 –40 0.30 –4 0.25 VOLTAGE (V) –2 –12 0.05 4.4 4.6 4.8 5.0 RECEIVER OUTPUT VOLTAGE (V) Figure 21. Output Current vs. Receiver Output High Voltage 12 10 8 6 4 2 0.2 0.4 0.6 0.8 1.0 1.
PAGE 12
ADM2491E Data Sheet CIRCUIT DESCRIPTION ELECTRICAL ISOLATION TRUTH TABLES In the ADM2491E, electrical isolation is implemented on the logic side of the interface. Therefore, the part has two main sections: a digital isolation section and a transceiver section (see Figure 25). The driver input signal, which is applied to the TxD pin and referenced to logic ground (GND1), is coupled across an isolation barrier to appear at the transceiver section referenced to isolated ground (GND2).
PAGE 13
Data Sheet ADM2491E 100 The limitation on the ac magnetic field immunity of the iCoupler is set by the condition that induced an error voltage in the receiving coil (the bottom coil in this case) that was large to either falsely set or reset the decoder. The voltage induced across the bottom coil is given by  dβ  V    rn 2 ; n  1, 2, . . . , N  dt  where (if the pulses at the transformer output are greater than 1.0 V in amplitude): β is the magnetic flux density (gauss).
PAGE 14
ADM2491E Data Sheet APPLICATIONS INFORMATION PCB LAYOUT The ADM2491E requires isolated power capable of 5 V at up to approximately 75 mA (this current is dependent on the data rate and termination resistors used) to be supplied between the VDD2 and the GND2 pins. A transformer driver circuit with a center-tapped transformer and LDO can be used to generate the isolated 5 V supply, as shown in Figure 28. The center-tapped transformer provides electrical isolation of the 5 V power supply.
PAGE 15
Data Sheet ADM2491E TYPICAL APPLICATIONS Figure 30 and Figure 31 show typical applications of the ADM2491E in half-duplex and full-duplex RS-485 network configurations. Up to 32 transceivers can be connected to the RS-485 bus.
PAGE 16
ADM2491E Data Sheet 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.