A small investment in over-voltage protection for high value FPGAs, ASICs, and micro processors could pay dividends in reliability, safety and warranty costs

The widening gap between the 24V-28V intermediate bus commonly found in industrial, aerospace and defense systems and the input supply voltages of modern digital processors presents design risk that could easily result in system failure, noxious smoke or even worse a fire. A relatively higher input voltage makes it increasingly difficult to maintain power supply voltages within the safe limits of the processor and has direct implications to the product in terms of size, operating costs, safety and reliability. These risks of overvoltage include but are not limited to:

1. Input surge events on the intermediate power bus.
2. Slight inaccuracies in the PFM/PWM timing of the switching regulator.
3. Erroneous, gray market or counterfeit capacitors introduced during manufacturing.

While most firms deny that illegitimate electronic components could ever enter their assembly line, customer support calls we’ve received at Analog Devices, discussions with our peers at other IC firms and even a US Senate Committee report released in May 2012 unfortunately indicate black market and counterfeit electronic components are a regular occurrence even at the most reputable companies and in the most secure applications.

Any one of these three events could cause output voltage excursions exceeding the load’s ratings potentially causing the costly FPGA, ASIC or microprocessor to be permanently damaged and in some extreme cases ignite. Depending on the extent of the damage, the root cause may be quite challenging to determine and the resulting high repair costs, lost customer productivity and harm to your reputation extremely frustrating.

If your system employs a intermediate voltage bus, a risk mitigation plan deserves your consideration to minimize cost and inconvenience to customers. Traditional overvoltage protection schemes involving a fuse are not suitable for protecting modern FPGAs, ASICs and microprocessors, particularly when the upstream voltage rail is 24V or 28V nominal. The response time is highly variable and too inaccurate to guarantee protection in such a high input-to-output voltage ratio application. Moreover, even if the digital logic device is successfully protected, the recovery process is lengthy and the resulting downtime irritating to clients as human intervention is necessary to replace the fuse before attempting a system restart.

A new solution has been created, combining an LTM4641 38V-rated, 10A DC/DC µModule switching regulator with circuitry to defend against many faults, including output overvoltage to protect high value FPGAs, ASICs or microprocessors. In case of an overvoltage event at the load, every regulator is tested at the factory and guaranteed to engage protection within 500ns before it ever reaches a customer. Furthermore, recovery is fast and simple. Simply toggle a logic level control pin to resume normal operation assuming the fault has cleared otherwise the protection will immediately engage again indicating a more serious problem. Power and protection for today’s most advanced digital logic devices are now available in one compact surface mount device. Watch this 2 minute Techclip Video for a demonstration: