12V Hot Swap Control

Reference Design LogoA hot-swap controller is used to limit the inrush current when a circuit board is plugged into a powered backplane. In addition a hot-swap controller may offer some or all of the following features: over current protection (electronic circuit breaker), over-voltage protection, and under-voltage protection. Hot-swap controllers are also required to isolate the board from the backplane which is useful in troubleshooting, maintenance, and upgrade activities. The power-down request may come from the backplane (remote) or an on-board switch (manual).

This reference design demonstrates how a Power Manager II ispPAC-POWR1220AT8 can be used to implement the functions required for +12V hot-swap applications. This reference design is compatible with the Power Manager II Hercules Development Kits.


  • Programmable inrush current limit (default 2 Amps)
  • Programmable de-bounce delay (default 30ms)
  • Programmable over current limit (default 15 Amps)
  • Over and under Voltage limits both at source and load
  • Short circuit protection
  • Programmable SOA drive of N-channel MOSFET
  • Power supply Or-ing

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Block Diagram

12V Hot Swap Control

Performance and Size

Tested Devices* Macrocells Product Terms VMONs I/Os HVOuts Timers Revision
ispPAC-POWR1220AT8 14 57 3 1/1 1 3 1.0

* May work in other devices as well.

Note: The performance and design sizes shown above are estimates only. The actual results may vary depending upon the chosen parameters, timing constraints, and device implementation. See the design's documentation for details. All coding and design work was done on a PC platform unless noted otherwise. 


Technical Resources
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12V Hot Swap Control - Documentation
RD1068 1.0 4/26/2010 PDF 469.8 KB
12V Hot Swap Control - Source Code
RD1068 1.0 4/26/2010 ZIP 371.1 KB

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