Many commercially available advanced-technology CMOS and bipolar integrated circuits are susceptible to single-event latchup (SEL) effects caused by heavy ions or protons from cosmic rays or solar flares, making them unsuitable for satellite applications. Remanufacturing the integrated circuits in an inherently SEL-immune process has been an expensive and technically difficult option, as is the alternate option of incorporating latchup protection and recovery circuitry in the spacecraft system's electronics.
Space Electronics Inc. has developed several different circuits that provide protection and recovery of integrated circuits known to exhibit single-event-induced latchup. These circuits are integrated within the same package as the susceptible integrated circuit using multichip module (MCM) and modern packaging technology, resulting in a device-level solution providing minimum cost and minimum impact on the system
The Latchup Protection Technology (LPT™) circuit was designed to provide current limiting to the device, detect the increase in current during the SEL event above a preset threshold, force a shutdown when the threshold is exceeded, hold the device in the shutdown mode for a preset time interval, and return the device's supply voltage to its original operating level.
The LPT circuitry (patent pending) has the potential to be applied to a wide variety of susceptible devices. The specific implementation details such as current latchup protection threshold and supply off time are determined by characterization of the susceptible devices at a heavy ion facility. The LPT device converts a single-event latchup into a recoverable event.
Two devices were evaluated with LPT: the ADS7805 16-bit analog-to-digital converter and the Gatefield GR10009 9000-gate flash programmable gate array. The first was selected for latchup protection, and the preliminary circuit design and analysis was based on protecting the ADS7805 device, which is susceptible to SEL at low linear energy transfer levels.