Hot socketing refers to the capability to insert a board into or remove a board from a system during system operation without causing negative effects to the system or the board. It is also referred to as "hot swapping" or "hot plug-in".

Altera offers on-chip hot-socketing and power-sequence-protection support and characterization proof data for 130-nm FPGA families. The Stratix®, Stratix GX, and Cyclone® FPGA families and the MAX® 7000AE, and MAX 3000A CPLD families are designed and tested to offer robust support for on-chip hot socketing and power-sequence protection without needing additional external devices or board manipulation. The 90-nm Stratix II and Cyclone II FPGA families and the 0.18-um MAX II CPLD family also support on-chip hot socketing and power-sequence-protection capability.

To be considered a hot-socketable device, the device must meet three criteria:

• It can be driven before power-up without any damage
• It does not drive out before or during power-up
• External input signals to the device’s I/O pins do not power its VCCIO or VCCINT power supplies through the device’s internal paths

To find out more about the advantages of the on-chip hot-socketing support in Altera FPGA devices, refer to the white paper Altera FPGA Hot-Socketing & Power-Sequencing Advantages that details Altera FPGA’s hot-socketing advantages. For detailed characterization data, refer to the white paper Hot-Socketing & Power-Sequencing Feature & Testing for Altera FPGA Devices.

For detailed characterization data, refer to the white paper detailing hot-socketing features and testing for Stratix II, Cyclone II, Stratix, Stratix GX, and Cyclone FPGA families and MAX II, MAX 7000AE, and MAX 3000A CPLD families.

Hot Socketing & Power-Sequence Protection in PLDs for High-Availability Systems

Hot socketing is a critical requirement for systems that require high availability (constant system uptime), such as network storage servers or carrier-class telecommunication infrastructures, where each second of system downtime translates directly into revenue losses.

Hot Socketing & Power-Sequence Protection in PLDs for Multi-Voltage Systems

In multi-voltage systems for which hot socketing is not required, hot-socketing and power-sequence-protection capability of the PLDs still can be critical. In these systems, regulators are used to provide different voltage levels and can cause the power-up sequence to become unpredictable; devices that require a predetermined power-up sequence may no longer function properly. PLDs’ hot-socketing support can alleviate problems in multi-voltage system designs because normal PLD functionality will not be influenced by the system power-up sequence. This can be vital for the common application where CPLDs are used to control the power-up of other devices in very complex systems.

Table 1 outlines some example systems in different market segments that benefit from hot socketing.

On-Chip Hot Socketing & Power-Sequencing Support Advantages

There are several techniques used to ensure that PLDs function properly during hot socketing, including sequence connectors and discrete hot-swap controllers. Table 2 compares hot socketing in Altera FPGA PLDs versus using other techniques.