1756-L73 Allen-Bradley ControlLogix 5570 PAC Controller Module

Product Description

The 1756-L73 is a high-performance Programmable Automation Controller (PAC) belonging to the ControlLogix 5570 product category. Engineered for large-scale factory automation and complex process applications, this processor supports both simplex and high-availability redundant topologies. It features 8 Megabytes of user memory and 0.98 Megabytes of dedicated I/O memory. Utilizing integrated energy storage technology, the 1756-L73 eliminates the need for lithium batteries to retain volatile memory contents during power cycles.

Global PLC Spare HUB Insight

The ControlLogix 1756-L73 is a cornerstone of mid-to-large tier Rockwell Automation architectures. By separating user execution memory from I/O processing space, it sustains fast scan times even when handling high-density communication tasks. Its native USB 2.0 port significantly reduces commissioning time compared to legacy serial interfaces, enabling rapid firmware flashing and diagnostic access. This module represents a reliable long-term asset for plants transitioning away from older hardware generations without rewriting legacy logic.

Target Equipment Compatibility

This processor installs directly into any standard or corrosion-resistant ControlLogix chassis:

• Standard Chassis Series: 1756-A4, 1756-A7, 1756-A10, 1756-A13, 1756-A17
• Conformal Coated K-Chassis Variants: 1756-A4K, 1756-A7K, 1756-A10K, 1756-A13K, 1756-A17K
• Standard Power Units: 1756-PA50, 1756-PA72, 1756-PA75, 1756-PB50, 1756-PB72, 1756-PB75, 1756-PH75
• Redundant Power Systems: 1756-PA75R, 1756-PA75RK, 1756-PB75R, 1756-PB75RK, 1756-PSCA2, 1756-PSCA2K

Technical Specifications

• Brand: Allen-Bradley / Rockwell Automation
• Model Number: 1756-L73
• Controller Series: ControlLogix 5570
• Module Type: Central Processing Unit (CPU)
• User Application Memory: 8 Megabytes
• I/O Memory Allocation: 0.98 Megabytes
• Total Digital I/O Capacity: 128,000 signals maximum
• Total Analog I/O Capacity: 4,000 signals maximum
• Task Architecture: 32 concurrent execution tasks
• Program Capacity: 100 applications per individual task
• Local Interface: One USB 2.0 port operating at 12 Mbps full speed
• Supported Networks: EtherNet/IP, ControlNet, DeviceNet, SynchLink, DH+, Remote I/O (RIO)
• Integrated Motion: Supports SERCOS, analog motion, and CIP Motion over EtherNet/IP
• Programming Languages: Ladder Diagram (LD), Structured Text (ST), Function Block Diagram (FBD), Sequential Function Chart (SFC)
• Backplane Current Draw (5.1V DC): 800 mA
• Backplane Current Draw (1.2V DC): 5 mA
• Power Dissipation: 2.5 Watts
• Thermal Dissipation: 8.5 BTU per hour
• Continuous Isolation Voltage: 30 Volts continuous (basic insulation type)
• Dielectric Test Rating: 500V AC for 60 seconds duration
• Wiring Category: Category 3 on USB port paths
• Physical Width: Single-slot form factor
• Enclosure Rating: Open-style construction (0.25 kg net weight)
• Operating Ambient Temperature: 32 to 140 degrees Fahrenheit (0 to 60 degrees Celsius)
• Storage Temperature Range: -40 to 185 degrees Fahrenheit (-40 to 85 degrees Celsius)
• Relative Humidity Range: 5 to 95 percent non-condensing levels
• Operating Vibration Resistance: 2 g acceleration at 10 to 500 Hz frequency
• Operating Shock Rating: 30 g peak force
• Non-Operating Shock Limit: 50 g peak force (45 g with Secure Digital card inserted)

Diagnostic & Fault Management Capabilities

• Integrated execution engine tracks onboard tasks and registers event triggers.
• The processing unit performs continuous background memory integrity checks.
• Status metrics report communication health over local backplane networks.
• Hardware registers capture specific program fault traps immediately.
• Real-time operational diagnostics stream directly via the built-in USB portal.

Typical Process Scenarios

• High-axis coordinated motion control loops across automated assembly lines.
• Large-scale distributed remote I/O management in wastewater facilities.
• Hot-standby redundant control configurations within power generation applications.
• Specialized oil and gas pipeline data concentration across legacy fieldbuses.

Procurement & Selection Guidance

• Verify that your application logic and tag databases do not exceed the 8MB memory threshold.
• Choose this controller if your safety or uptime specifications demand hardware redundancy.
• Ensure you possess Studio 5000 Logix Designer software compatible with 5570 hardware.
• Select matching K-prefix parts if your environment requires conformal coating protection.

Logistics, Delivery & Warranty Terms

• Dispatch Window: Orders process and dispatch within 24 to 48 hours following payment confirmation.
• Shipping Carriers: Express global transport managed by FedEx, UPS, and DHL Express.
• Warranty Coverage: Includes a comprehensive 12-month industrial performance warranty starting from the ship date.

Frequently Asked Questions

How does the battery-less energy storage module function on this processor during extended outages?

The integrated capacitor structure charges automatically from backplane power during normal system operation. Upon main power loss, this stored charge provides enough energy to copy volatile execution memory into onboard non-volatile flash storage safely.

Can this unit reside alongside legacy modules in an older 1756 series backplane?

Yes, the processor works within all standard 1756 chassis options. However, you must verify that the installed power supply meets the specific dual-voltage requirement of 800 mA at 5.1V DC and 5 mA at 1.2V DC.

What is the practical impact of having 0.98 MB of dedicated I/O memory separated from user memory?

This dual-zone design ensures that heavy network traffic or large I/O configurations do not consume the memory space needed for application code execution. It stabilizes scan times and prevents program crashes caused by memory allocation overflows.

Which firmware version is required to implement redundancy with this module?

Redundant topologies require specific enhanced redundancy firmware bundles inside Studio 5000. You must reference the Rockwell Product Compatibility and Download Center (PCDC) to match your exact hardware series with the certified redundancy revision.

Is an external Secure Digital card required for the system to execute its program loops?

No, the controller executes programs directly out of its internal volatile memory space. The optional industrial SD card serves as a non-volatile backup for manual firmware loads or user code restoration when servicing field equipment.

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