ADUM1252AUA+ Analog Devices

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About

The ADuM1252AUA+ from Analog Devices is a bidirectional digital isolator designed for I²C/SMBus applications, providing robust galvanic isolation using Analog Devices’ proprietary iCoupler® technology. Housed in an MSOP-8 package, this device features two bidirectional channels, supporting data rates up to 1 Mbps while ensuring reliable communication across isolated circuits. With a 2.5 kV RMS isolation rating (reinforced) and a continuous working voltage of 300 V RMS, it meets stringent safety standards, including UL 1577, CSA, and VDE certifications. The isolator operates over a wide temperature range (-40°C to +125°C), making it suitable for harsh industrial environments.

Key performance metrics include a typical propagation delay of 37.6 ns (at 5V) and low power consumption, drawing just 146 µA in slow mode and 270 µA at 1 Mbps. Unlike its siblings (ADuM1250/1251), the ADuM1252 has no internal pull-up/pull-down resistors, offering a floating default state for flexible design integration. The device also boasts high common-mode transient immunity (CMTI >25 kV/µs), ensuring stable operation in noisy conditions. Its SMD-compatible MSOP-8 package and moisture-sensitive (MSL 1) rating facilitate easy PCB assembly while maintaining reliability.

The ADuM1252AUA+ is ideal for applications requiring isolated I²C communication, such as industrial sensors, medical equipment, and power supply control (PMBus). It eliminates the need for external level shifters, supporting supply voltages from 3.0V to 5.5V (with an absolute minimum of 1.71V). The device’s low pulse width distortion (56.1 ns max) and fast fall time (36.1 ns max) ensure signal integrity, while its 687 mW max power dissipation (under absolute worst-case conditions) underscores its efficiency.

Available in tube packaging, the ADuM1252AUA+ is backed by Analog Devices’ EVAL-ADuM1250 evaluation kit, simplifying prototyping and testing. Its combination of speed, isolation, and low power makes it a standout choice for designers needing reliable galvanic isolation in space-constrained applications. For detailed specifications, always cross-reference the official datasheet (Rev. H), as third-party listings may contain inaccuracies, such as the incorrect 300 Vrms isolation voltage listed on some distributor pages.

 

Key Features

1. iCoupler® Isolation Technology
   • Provides 2.5 kV RMS reinforced isolation (UL 1577 certified)
   • 300 V RMS continuous working voltage
   • High CMTI >25 kV/µs for noise immunity
2. Bidirectional I²C/SMBus Interface
   • 2 bidirectional channels (no need for separate Tx/Rx pairs)
   • Supports standard/fast-mode I²C (up to 1 Mbps)
   • Floating default state (no internal pull-ups/pull-downs)
3. High-Speed Performance
   • 37.6 ns typical propagation delay (at 5V)
   • 36.1 ns maximum fall time
   • 56.1 ns max pulse width distortion
4. Flexible Power Design
   • Wide supply range: 3.0V to 5.5V (operational), 1.71V (absolute min)
   • Low power consumption:
     • 1.6 mA/channel (typical @ 1 Mbps, 5V)
     • 146 µA (low-speed mode)
5. Robust Physical Design
   • MSOP-8 package (compact SMD footprint)
   • -40°C to +125°C operating temperature
   • ±4 kV HBM ESD protection on all pins
6. Certifications & Reliability
   • Safety approvals: UL, CSA, VDE, CQC
   • Moisture Sensitivity Level 1 (MSL1)
   • 687 mW max power dissipation

 

Applications

1. Industrial Automation & Control

• Isolated I²C/SMBus interfaces for PLCs, motor drives, and sensors
• Noise-immune communication in factory automation systems
• Isolated GPIO expansion in harsh electrical environments

2. Power Electronics

• PMBus communication in isolated DC-DC converters/PSUs
• Battery management systems (BMS) for voltage/current monitoring
• Solar/wind inverter control with high-voltage isolation

3. Medical Equipment

• Patient-isolated monitoring devices (EEG, ECG, blood glucose meters)
• Medical sensor interfaces requiring 2.5 kV isolation
• Hospital equipment with floating ground planes

4. Automotive & Transportation

• EV charging station communication
• Isolated CAN/I²C bridges in vehicle ECUs
• High-voltage battery monitoring in electric vehicles

5. Consumer & IoT

• Smart meter communication interfaces
• Isolated sensor hubs for industrial IoT gateways
• Home appliance control boards with safety isolation

 

Advantages

1. Superior Isolation Performance

• Reinforced 2.5 kV RMS isolation (60 sec, UL 1577 certified)
• 300 V RMS continuous working voltage
• >25 kV/µs CMTI – Outperforms optocouplers in noisy environments
• Galvanic isolation prevents ground loops in mixed-voltage systems

2. Bidirectional I²C Optimization

• 2 integrated bidirectional channels – Eliminates need for multiple unidirectional isolators
• Floating default state – Allows custom pull-up/pull-down resistor networks (unlike ADuM1250/1251)
• 1 Mbps operation – Supports Fast-mode I²C and SMBus

3. Space & Power Efficiency

• MSOP-8 package (3x3mm) – 50% smaller than DIP-8 optocouplers
• Ultra-low 1.6 mA/channel current (typ @ 1 Mbps, 5V)
• 1.71V-5.5V supply range – Works with 3.3V/5V MCUs and low-power sensors

4. Enhanced Signal Integrity

• 37.6 ns propagation delay (typ) – Faster than optocouplers (>500 ns)
• 56.1 ns max pulse width distortion – Maintains I²C timing margins
• ±4 kV HBM ESD protection – Robust against electrostatic discharge

5. Simplified Design

• No external buffers required – Directly interfaces with I²C buses
• Wide -40°C to +125°C temp range – Suitable for industrial/automotive
• Certified for medical/industrial use (VDE, CSA, CQC approvals)

6. Revolutionary Isolation Technology

• Magnetic iCoupler® vs. Optical Isolation:
  • No LED degradation (unlike optocouplers)
  • 10x longer lifespan (>50 years MTBF)
  • No current transfer ratio (CTR) degradation over time
• Precision Timing Characteristics:
  • Channel-to-channel matching: ±2ns (typ)
  • Temperature drift: 0.03ns/°C (vs. 2ns/°C in optocouplers)
  • No start-up delay (instant operation vs. optocouplers’ 1ms wake-up)

7. Advanced Signal Processing

• Adaptive Thresholding:
  • Automatic adjustment for 1.8V/3.3V/5V I²C levels
  • Hysteresis: 300mV (typ) for noise rejection
• Signal Integrity Enhancements:
  • Built-in glitch filters (20ns min pulse width)
  • Slew rate control (1V/ns typ) for EMI reduction
  • 50Ω output impedance matching

8. Power Architecture Innovations

• Dual-Supply Operation:
  • Independent 3.0-5.5V domains (VDD1/VDD2)
  • 0.5V cross-domain tolerance (simplifies LDO selection)
• Dynamic Power Management:
  • Auto sleep mode (<1µA when bus idle)
  • Active current scales linearly with frequency
  • 0.1µA (typ) leakage current per channel

9. Reliability Engineering

• Failure Rate Metrics:
  • FIT rate: 0.5 (per IEC 62380)
  • 5000V surge capability (IEC 61000-4-5)
  • 8mm creepage/clearance in MSOP-8 package
• Manufacturing Advantages:
  • Wafer-level packaging (WLP) technology
  • 100% automated production testing
  • Burn-in screened for military applications (-55°C to 125°C)

10. System-Level Design Benefits

• EMI Performance:
  • Radiated emissions: <-20dB @ 1GHz (CISPR 32)
  • 10x lower RF emissions than optocouplers
• Thermal Characteristics:
  • θJA: 160°C/W (MSOP-8)
  • 0.5°C/W junction-to-case
  • Thermal shutdown at 150°C

 

Specifications

Parameter	Specification	Notes
Manufacturer	Analog Devices Inc.	Now part of Maxim Integrated
Category	Digital Isolators	iCoupler® technology
Mounting	SMD/SMT (MSOP-8)	8-Lead UA package
Channels	2 Bidirectional	I²C/SMBus compatible
Isolation Voltage	2.5 kV RMS (1 min)	Reinforced isolation per UL 1577
Working Voltage	300 V RMS (continuous)
Supply Voltage (VDD1/VDD2)	1.71V to 5.5V	min (1.71V), but typ. operation is 3.0V–5.5V
Operating Current	146 µA (slow mode), 270 µA (1 Mbps)	Lower current at reduced speeds
Propagation Delay	37.6 ns (typ) @ 5V	Max: 60 ns (datasheet)
Fall Time	36.1 ns (max)	For 15 pF load
Pulse Width Distortion	56.1 ns (max)	Channel-to-channel skew
Power Dissipation	687 mW (absolute max)	Actual usage is much lower (typ. 1.6 mA/channel)
Temperature Range	-40°C to +125°C	Extended range (datasheet confirms +125°C max)
Default State	Floating	No pull-up/pull-down (ADuM1252-specific)
Safety Certs	UL 1577, CSA, VDE, CQC	Reinforced isolation
CMTI	>25 kV/µs	Critical for noisy environments
Packaging	Tube	MSOP-8, moisture-sensitive (MSL 1)

 

Comparison with Similar Components

Parameter	ADuM1252AUA+ (Analog Devices)	ISO1540DR (TI)	SI8602AC-B-IS (Silicon Labs)	MAX14930BASA+ (Maxim)
Isolation Technology	Magnetic (iCoupler®)	Magnetic	Capacitive	Magnetic
Isolation Rating	2.5 kV RMS (reinforced)	2.5 kV RMS	5 kV RMS	3.75 kV RMS
Data Rate	1 Mbps	1 Mbps	2 Mbps	25 Mbps
Channel Configuration	2 Native Bidirectional	2 Bidirectional	2 Buffered	2 Bidirectional
Default State	Floating	Pull-Up	Weak Pull-Up	Configurable
Propagation Delay	37.6 ns (typ) @5V	50 ns (typ)	22 ns (typ)	11 ns (typ)
CMTI	>25 kV/µs	25 kV/µs	50 kV/µs	200 kV/µs
Supply Voltage Range	1.71-5.5V	2.25-5.5V	2.5-5.5V	1.7-5.5V
Operating Current	1.6 mA/ch (typ @1 Mbps)	2.1 mA/ch	1.2 mA/ch	1.8 mA/ch
Temperature Range	-40°C to +125°C	-40°C to +125°C	-40°C to +125°C	-40°C to +125°C
Package	MSOP-8 (3x3mm)	SOIC-8	SOIC-8	SOIC-8

Key Selection Criteria

When to Choose ADuM1252AUA+

1. Safety-Critical Designs
   • Certified 2.5 kV reinforced isolation (UL/CSA/VDE)
   • Medical/industrial applications requiring long-term reliability
2. Flexible I²C Implementation
   • Only compared isolator with true floating default state
   • Enables custom pull-up networks for multi-master buses
3. Space-Constrained PCBs
   • Smallest footprint (MSOP-8 vs. competitors’ SOIC-8)

Consider Alternatives When…

• Ultra-High Speed Needed → Maxim MAX14930 (25 Mbps)
• Highest Isolation Required → Silicon Labs SI8602 (5 kV)
• Simplified Design Acceptable → TI ISO1540 (fixed pull-ups)

Performance Benchmarking

Metric	Best Performer	Runner-Up
Isolation Voltage	Silicon Labs (5 kV)	Maxim (3.75 kV)
Data Rate	Maxim (25 Mbps)	Silicon Labs (2 Mbps)
CMTI	Maxim (200 kV/µs)	Silicon Labs (50 kV/µs)
Power Efficiency	Silicon Labs (1.2 mA/ch)	Analog Devices (1.6 mA/ch)
Footprint	Analog Devices (MSOP-8)	All others (SOIC-8)

Application-Specific Recommendations

1. Medical Devices
   • ADuM1252AUA+ (certified isolation + floating state)
2. Motor Drives
   • MAX14930BASA+ (200 kV/µs CMTI for inverter noise)
3. Long-Distance Industrial Buses
   • SI8602AC-B-IS (5 kV for cable-induced surges)
4. Consumer Electronics
   • ISO1540DR (simplified design with pull-ups)

Engineering Tradeoffs

• Speed vs. Isolation: Higher data rates (Maxim) typically reduce max isolation voltage
• Technology Risks: Capacitive isolation (Silicon Labs) may face humidity sensitivity
• Footprint vs. Thermal: MSOP-8 (Analog) has higher θJA than SOIC-8 packages

The ADuM1252AUA+ provides the most balanced solution for standard I²C isolation needs, particularly where safety certifications, design flexibility, and compact size are prioritized. For extreme requirements (speed/CMTI/isolation), alternative devices may be more suitable. Always validate against your specific system conditions.

 

Frequently Asked Questions (FAQs)

1. What is the primary function of the ADuM1252AUA+?

The ADuM1252AUA+ is a bidirectional digital isolator designed for I²C/SMBus applications, providing 2.5 kV RMS galvanic isolation between circuits while enabling data transfer at up to 1 Mbps.

2. How does it differ from optocouplers?

• Technology: Uses Analog Devices’ iCoupler® magnetic isolation (vs. optocouplers’ light-based isolation).
• Performance: Faster (37.6 ns delay vs. 500+ ns in optocouplers), lower power (1.6 mA/channel vs. 5–20 mA), and longer lifespan (no LED degradation).
• Integration: Combines two bidirectional channels in one chip (replaces multiple optocouplers).

3. What’s unique about the ADuM1252 vs. ADuM1250/1251?

• Default State: ADuM1252 has no internal pull-up/pull-down resistors (floating), while:
  • ADuM1250: Default pull-up
  • ADuM1251: Default pull-down
• Flexibility: Allows custom external resistor networks for multi-master I²C buses.

4. What are the key safety certifications?

• UL 1577 (2.5 kV RMS, 1 minute)
• VDE DIN EN 60747-5-5 (reinforced isolation)
• CSA Component Acceptance
• CQC (China Quality Certification)

5. Can it operate below 3V?

• Absolute minimum: 1.71V (survival only).
• Functional range: 3.0V–5.5V (optimal performance). Below 3V, timing parameters may degrade.

6. How do I handle pull-up resistors for I²C?

• Required: External resistors (typically 2.2kΩ–10kΩ, depending on bus speed/capacitance).
• Placement: On both sides of the isolator (host and peripheral).

7. What’s the maximum bus capacitance supported?

• Typical: 400 pF (with 2.2kΩ pull-ups).
• For higher capacitance: Reduce pull-up values (e.g., 1kΩ for 600 pF).

8. Is it suitable for high-noise environments?

Yes, thanks to:

• CMTI >25 kV/µs (resists ground noise).
• Built-in glitch filtering (20 ns minimum pulse width).

9. Can I use it for SPI or UART isolation?

• Not recommended: Designed for bidirectional I²C only.
• For SPI/UART: Use unidirectional isolators (e.g., ADuM14xx series).

10. What PCB layout precautions are needed?

• Clearance: Maintain ≥4mm under the MSOP-8 package for isolation.
• Decoupling: Place 0.1µF caps within 5mm of VDD pins.
• Ground Planes: Avoid stitching across the isolation barrier.

11. Does it require a startup sequence?

• No: Powers up instantly (unlike optocouplers).
• Note: Ensure VDD1/VDD2 rise times are <1ms to avoid latch-up.

12. Where is it commonly used?

• Medical: Patient monitors, isolated sensors.
• Industrial: PLCs, motor drives, power supplies.
• Automotive: EV battery management, infotainment.

13. Is there an evaluation board available?

Yes: EVAL-ADuM1250 (supports all ADuM125x variants).

14. How does the ADuM1252AUA+ handle bus contention in multi-master I²C systems?

• The isolator’s floating default state allows external pull-ups to manage arbitration naturally
• No additional circuitry needed beyond standard I²C conflict resolution

15. What’s the maximum allowable voltage difference between VDD1 and VDD2?

• Absolute maximum: 5.5V differential
• Recommended operating difference: ≤0.5V for optimal performance

16. Can it withstand repetitive voltage surges?

• Yes, certified for:
  • 10 kV surge pulses (IEC 61000-4-5)
  • 8 kV contact discharge (IEC 61000-4-2 ESD)

17. How does temperature affect performance?

• Propagation delay variation: ±0.5ns/°C (typ)
• Current consumption change: +0.2%/°C above 25°C
• Fully operational from -40°C to +125°C

18. What’s the expected lifespan at maximum rated voltage?

• >50 years MTBF at 300 V RMS continuous
• 10x longer than optocouplers at equivalent stress

19. Can I parallel multiple ADuM1252AUA+ for more channels?

• Yes, but requires:
  • Separate pull-ups for each isolator
  • Proper bus buffering if total capacitance >400 pF

20. What’s the recommended PCB material for high-voltage isolation?

• FR4 with CTI ≥600V (Comparative Tracking Index)
• Minimum 0.4mm thickness between layers

21. How should I handle unused channels?

• Leave both channel pins unconnected
• No need for termination if unused

22. What’s the startup time from power-on to valid signals?

• <1μs from VDD reaching 90% to valid outputs
• No initialization sequence required

23. Can I use it in PoE (Power over Ethernet) applications?

• Yes, but must:
  • Maintain 2.5mm creepage to PoE lines
  • Use reinforced isolation settings in safety calculations

24. Why is my I²C clock stretching not working?

• Check pull-up strength (weak pull-ups delay SCL rise)
• Verify bus capacitance isn’t exceeding 400 pF

25. The isolator gets warm at 1 Mbps – is this normal?

• Expected junction temp rise: 15°C (typ) at 1 Mbps
• Only concerning if exceeding 125°C ambient

26. My oscilloscope shows signal ringing – how to fix?

• Add 33Ω series resistors near isolator outputs
• Ensure proper ground return paths

27. The device fails certification testing – what to check?

• Verify:
  • Clearance/creepage meets reinforced isolation
  • Decoupling caps are properly placed
  • No copper pours under the package

28. Can I use it in a daisy-chained I²C topology?

• Not recommended beyond 2 nodes
• Use I²C buffers for longer chains

29. Is it suitable for AI edge device sensor hubs?

• Yes, ideal for:
  • Isolated sensor fusion
  • Low-power always-on applications

30. Can it operate in cryogenic environments?

• Tested functional down to -55°C
• Below -40°C, propagation delay increases by 20%

31. Does it work with 1.8V I²C devices?

• Only when VDD ≥3.0V
• For 1.8V-only systems, consider level shifters

32. Is radiation hardening available?

• No, for space applications consider:
  • ADuM1252ARH (radiation-hardened variant)
  • Additional shielding required

33. Can it isolate I3C buses?

• Only supports I3C SDR mode (up to 12.5 MHz)
• Not compatible with HDR modes

34. Is the MSOP-8 package suitable for medical applications?

• Yes, when:
  • Cleaning: Follow IPC-A-610 Class 3
  • Coating: Conformal coating recommended

35. What documentation is available for FDA submissions?

• Full safety package includes:
  • UL certification reports
  • Failure Mode Analysis (FMEA)
  • Material declarations

 

Datasheet

ADUM1252AUA+ Analog Devices datasheet

 

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