CA-IS3722 High-Performance Dual-Channel Digital Isolator
Break through the barriers of industrial communication with the CA-IS3722 – a game-changing digital isolator that delivers ±150 kV/μs CMTI performance while maintaining blazing-fast 150 Mbps data rates. Engineered by Shanghai Chipanalog Microelectronics, this device sets new standards for noise immunity and reliability in harsh industrial environments.
Key Features
• Superior Noise Immunity – Industry-leading ±150 kV/μs CMTI outperforms TI and ADI competitors
• High-Speed Performance – DC to 150 Mbps data rate with ultra-low 12ns propagation delay
• Robust Isolation – Up to 5,000 VRMS isolation voltage for critical safety applications
• Extended Operating Range – 2.5V to 5.5V supply with -40°C to +125°C temperature range
• Bidirectional Architecture – 2 channels with 1 channel in each direction for flexible communication
• Multiple Package Options – SOIC8 narrow/wide body and SOIC16 wide body configurations
• Comprehensive Safety Certified – VDE 0884-17, UL 1577, IEC 61010-1 compliant
• Long Operational Life – >40 years with capacitive SiO2 isolation technology
• Low Power Consumption – 1.2mA per side at 3.3V DC operation
Technical Specifications
| Parameter | Specification | Units | Notes |
|---|---|---|---|
| Performance Specifications | |||
| Data Rate | DC to 150 | Mbps | Continuous operation from DC to maximum speed |
| Propagation Delay | 12 (typical) | ns | Best-in-class timing performance |
| Propagation Delay Skew | 2 (chip-to-chip) | ns | Excellent channel matching |
| Pulse Width Distortion | 1 | ns | Minimal signal distortion |
| Minimum Pulse Width | 5 | ns | High-frequency capability |
| Isolation Specifications | |||
| Isolation Voltage Rating | Up to 3,500 | VRMS | Robust isolation barrier |
| Common Mode Transient Immunity (CMTI) | ±150 (typical) | kV/μs | Superior noise immunity |
| Isolation Barrier Lifetime | >40 | years | Long-term reliability |
| Isolation Technology | Capacitive SiO₂ | – | Robust isolation barrier |
| Electrical Specifications | |||
| Supply Voltage Range | 2.5 to 5.5 | V | Wide supply range compatibility |
| Operating Temperature Range | -40 to +125 | °C | Extended temperature operation |
| Default Output State | High | – | Fail-safe operation |
| Power Consumption (VDD = 5.0V) | |||
| Power @ 1 Mbps | 1.5 per channel | mA | Low power consumption |
| Power @ 100 Mbps | 6.6 per channel | mA | Efficient high-speed operation |
| Operational Features | |||
| Startup Initialization | None required | – | Immediate operation |
| Channel Configuration | 2 channels bidirectional | – | Ideal for Tx/Rx isolation |
| Default Output Behavior | High when input unpowered/open | – | Safe system operation |
Why Bidirectional Architecture Matters for Transceiver Isolation
The Fundamental Challenge
Most communication protocols like RS-485, CAN, and UART require simultaneous bidirectional data flow – one channel transmitting (Tx) while the other receives (Rx). Traditional isolation solutions required two separate unidirectional isolators, creating design complexity, increased cost, and potential timing mismatches.
The CA-IS3722’s 2-channel bidirectional architecture solves this elegantly:
- Channel 1: Side A → Side B (e.g., Tx isolation)
- Channel 2: Side B → Side A (e.g., Rx isolation)
RS-485 Transceiver Isolation Applications
Typical RS-485 Implementation
MCU/Controller ←→ CA-IS3722 ←→ RS-485 Transceiver ←→ Network
(Side A) (Side B)
Pin Configuration:
- VI1 (Side A): Connected to MCU Tx pin
- VO1 (Side B): Connected to RS-485 transceiver DI (Data Input)
- VI2 (Side B): Connected to RS-485 transceiver RO (Receiver Output)
- VO2 (Side A): Connected to MCU Rx pin
Critical Applications
Industrial Automation Networks
- Factory Floor Communication: Isolate PLCs from field devices across noisy factory environments
- Process Control Systems: Protect control rooms from ground loops in chemical plants
- Building Management: Isolate HVAC controllers from central monitoring systems
- Power Plant Monitoring: Protect control systems from high-voltage switchgear interference
Key Benefits:
- Ground Loop Elimination: Prevents differential ground potentials from disrupting communication
- Surge Protection: Protects expensive controllers from lightning and switching transients
- Noise Immunity: ±150 kV/μs CMTI ensures reliable data transmission in electrically harsh environments
- Long Distance Communication: Enables reliable RS-485 networks over kilometers of cable
CAN Bus Transceiver Isolation
CAN Network Architecture
ECU/Controller ←→ CA-IS3722 ←→ CAN Transceiver ←→ CAN Bus
(Side A) (Side B)
Signal Flow:
- CAN_Tx: MCU → VI1 → VO1 → CAN Transceiver TXD
- CAN_Rx: CAN Transceiver RXD → VI2 → VO2 → MCU
Automotive Applications
Electric Vehicle Systems
- Battery Management: Isolate cell monitoring units from high-voltage battery packs
- Charging Infrastructure: Protect charging station controllers from vehicle electrical systems
- Motor Control: Isolate inverter control from vehicle CAN network
- Safety Systems: Protect airbag and ABS controllers from electrical faults
Industrial CAN Networks
- Heavy Machinery: Isolate engine controls from hydraulic system networks
- Marine Electronics: Protect navigation systems from engine management CAN buses
- Agricultural Equipment: Isolate GPS guidance from tractor implement controls
- Medical Devices: Protect patient monitoring networks from power system interference
Advantages for CAN Applications
- Arbitration Protection: Prevents ground differentials from affecting CAN arbitration
- Fault Isolation: Protects entire network from single node electrical failures
- EMC Compliance: Reduces common-mode emissions in automotive applications
- Diagnostic Safety: Allows safe connection of diagnostic tools to live CAN networks
The Critical Importance of “Default Output High”
Fail-Safe Communication Behavior
When the input is unpowered or open-circuit, the CA-IS3722 defaults to high output. This seemingly simple feature provides crucial system benefits:
RS-485 Applications
Normal Operation:
- Logic High = RS-485 transceiver disabled (high impedance)
- Logic Low = RS-485 transceiver enabled (driving bus)
Fail-Safe Behavior:
- Power Loss: Transceiver automatically disables, preventing bus conflicts
- Cable Disconnect: No spurious bus activity that could disrupt network
- System Startup: Transceivers remain disabled until MCU properly initializes
CAN Applications
Recessive State Protection:
- CAN Logic: High = Recessive (non-dominant), Low = Dominant
- Network Safety: Default high ensures no unintended dominant bits during faults
- Bus Integrity: Prevents single node failures from monopolizing the CAN bus
UART/Serial Applications
Idle State Maintenance:
- UART Idle: High state indicates no data transmission
- Clean Startup: Receiving end sees proper idle state during system initialization
- Error Prevention: Prevents false start bits from corrupted power-up sequences
Advanced Transceiver Integration Examples
1. Isolated RS-485 Repeater
Network A ←→ RS-485 Transceiver ←→ CA-IS3722 ←→ RS-485 Transceiver ←→ Network B
- Galvanic Isolation: Completely separate network segments
- Ground Loop Prevention: Eliminate potential differences between network segments
- Surge Protection: Protect both network segments from electrical faults
2. Multi-Protocol Gateway
CAN Network ←→ CAN Transceiver ←→ CA-IS3722 ←→ Protocol Converter ←→ CA-IS3722 ←→ RS-485 Transceiver ←→ RS-485 Network
- Protocol Translation: Safely convert between different communication standards
- Dual Isolation: Protect both networks from electrical interference
- System Integration: Connect legacy RS-485 systems to modern CAN networks
3. Isolated USB-to-Serial Converter
USB Host ←→ USB-Serial IC ←→ CA-IS3722 ←→ RS-232 Transceiver ←→ Industrial Equipment
- PC Protection: Isolate expensive computers from industrial ground loops
- Hot-Plug Safety: Prevent ground current spikes during cable connection
- Diagnostic Safety: Enable safe connection to live industrial systems
Design Implementation Best Practices
1. Power Supply Architecture
- Dual Isolated Supplies: Provide separate power domains for each side
- Low Ripple Design: Minimize power supply noise to maintain signal integrity
- Decoupling Strategy: Place 0.1μF ceramic capacitors close to each VDD pin
2. PCB Layout Optimization
- Isolation Barrier: Maintain proper creepage/clearance distances
- Ground Plane Separation: Keep Side A and Side B ground planes isolated
- Signal Routing: Route high-speed signals away from isolation barrier
- Bypass Capacitors: Local decoupling for each power supply pin
3. Timing Considerations
- Propagation Delay: Account for 12ns typical delay in both directions
- Skew Matching: Ensure balanced delays for bidirectional protocols
- Setup/Hold Times: Verify timing margins for target communication speeds
4. Fault Protection
- ESD Protection: Additional TVS diodes for harsh environments
- Overcurrent Protection: Series resistors for transceiver protection
- Thermal Management: Adequate copper area for heat dissipation
Competitive Advantages for Transceiver Applications
1. Timing Performance
- 12ns Propagation Delay: Enables high-speed communication up to 150 Mbps
- 1ns Pulse Width Distortion: Maintains signal integrity for critical timing
- 5ns Minimum Pulse Width: Supports high-frequency digital protocols
2. Electrical Robustness
- ±150 kV/μs CMTI: Superior noise immunity compared to competitors
- 5000V Isolation: Meets stringent safety requirements for industrial applications
- Extended Temperature Range: -40°C to +125°C for harsh environments
3. System Integration
- Wide Supply Range: 2.5V to 5.5V accommodates various system voltages
- Default High Output: Ensures safe system behavior during faults
- Multiple Packages: Flexible form factors for different space constraints
The CA-IS3722’s bidirectional architecture with default high output makes it the ideal solution for any transceiver isolation application, providing robust, reliable, and cost-effective protection for critical communication links.
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