Understanding the distinction between MOD and SA power is the first hurdle for any engineer working with the CompactLogix 5380 or Compact 5000 I/O platform. Unlike older systems where power was often shared across the backplane, the 5069 series uses a dual-bus architecture to separate logic electronics from field-side power.
Two Buses Explained:
- MOD (Module) Power: This is the logic side. It powers the internal circuitry, communication chips, and LEDs of your PLC and I/O modules. It is strictly 24V DC.
- SA (Sensor/Actuator) Power: This is the field side. It provides the current that actually goes out to your proximity switches, solenoid valves, and relays. This can be DC or AC depending on the module.
Manual Calculation:
You need to sum the current for every single module in the local rack.
Step 1: The MOD Power Calculation
- Check the technical data for each module’s MOD Power Current.
- Sum the values for the Controller (or AENTR adapter) and every I/O module.
- Ensure the total is under 10 A.
Step 2: The SA Power Calculation
There are two components to SA Power:
- Internal SA Draw: Some modules (like analog or high-density digital) pull a small amount of power from the SA bus to run their output converters.
- Field Load: This is the sum of every device wired to the terminals. If you have 10 solenoids drawing 500mA each, that is 5 A of SA load. Ensure the total (Internal + Field) is under 10 A per bus.
Reference Table for 5069 Modules
| Module Type | Part Number | MOD Current (mA) | SA Current (mA) | Max LA Current / Channel (mA) |
|---|---|---|---|---|
| Controller | 5069-L320ER | 450 | 10*** / 25**** | n/a |
| Ethernet Adapter | 5069-AENTR | 220 | 5*** / 10**** | n/a |
| 16-point Digital Input (DC) | 5069-IB16 | 75 | 200 | n/a |
| 8-point Digital Output (DC) | 5069-OB8 | 75 | 0 | 2000 |
| 16-point Digital Output (DC) | 5069-OB16 | 75 | 0 | 500 |
| 16-point Digital Input (AC) | 5069-IA16 | 75 | 240 | n/a |
| 16-point Relay Output | 5069-OW16 | 75* / 225** | 150* / 0** | n/a |
| 8-point Analog Input | 5069-IF8 | 75 | 100 | n/a |
| 4-point Analog Output | 5069-OF4 | 75 | 150 | n/a |
Source: Data pulled from Rockwell Automation Publication 5069-TD001P-EN-P – March 2026
Note: Modules that use LA power do not use the SA power bus to power their own outputs; instead, they receive power via the LA+ and LA- terminals on the removable terminal block (RTB)
Additional Notes
- Always use separate separate branches for MOD and SA. This ensures that if a field device shorts out the SA bus, the MOD bus stays alive, keeping the PLC and communications online for troubleshooting.
- Don’t forget Inrush Current.
- Watch for Voltage Mixes. If you have 24V DC modules and 120V AC modules in the same rack, you must use a 5069-FPD to physically break the SA bus and prevent cross-voltage issues.