Compact Dual-Slot PCI Express Hot Swap Controller Provides Fault Protection

Together with analog current limit amplifiers, electronic circuit breakers with adjustable response time provide dual level over-current protection. Control for the auxiliary supplies is completely independent with separate ON and FAULT pins. The internal 3.3V AUX MOSFET features a low 0.25 Ohm ON resistance which, together with the exposed backside metal on the QFN package and thermal shutdown protection, minimizes heat in the device. A separate VCC pin allows the part to power up without the main supplies being present and the ability to ride out glitches in the auxiliary supply, ensuring continuous reliable operation.

The 5mm x 7mm QFN package is narrow enough to fit between the PCI Express connectors if needed for board space optimization. The optional leaded package, 36-pin SSOP, is a proprietary package designed for narrow applications, requiring less than 8mm including the landing area for the pins. Despite the small form factor, the controller offers independent control of the main and auxiliary supplies for each port, separate FAULT outputs for main and auxiliary supplies, power-good outputs for each slot and board-present inputs for each slot.

Specified over the commercial and industrial temperature ranges, the LTC4242 is offered in 5mm x 7mm 38-lead QFN and 36-lead SSOP packages. Available from stock, pricing begins at $3.30 each in 1,000 piece quantities.

For more sophisticated monitoring, Linear Technology also offers the single-slot LTC4245 which includes an integrated ADC and I2C interface for high-end PCI Express applications.