NASA Office of Logic Design

NASA Office of Logic Design

A scientific study of the problems of digital engineering for space flight systems,
with a view to their practical solution.

RTAX-S VCCA Transients

Updated May 14, 2006.

OLD News #18, "New FPGA Technologies: Currents, Voltages, and Temperatures," discusses the tight voltage limits on many modern FPGAs, including the RTAX-S series of FPGAs.  This makes the job of the power supply designer challenging, as not only must tight DC limits be met but AC transients, induced by radiation, must also be limited.  Radiation testing of a number of voltage regulators showed the effects of single event transients (SETs) on output voltage.  This note will describe a recent change in the RTAX-S military specification with regard to these transients.

The following is excerpted from the RTAX2000S SMD:

AC transient VCCA limit is for radiation induced transients less than 10µs duration, and not intended for repetitive use. Core voltage spikes from a single event transient will not negatively affect the reliability of the device if, for this non-repetitive event, the transient does not exceed 1.8 V at any time, and the total time that the transient exceeds 1.575 V does not exceed 10 µs in duration."

While this note is taken from the RTAX2000S SMD, it is expected that a similar specification will be contained in the SMD's for the other members of the RTAX-S family, the RTAX250S and the RTAX1000S.  This note will be updated when those SMD's are released..

Additionally, note that the RTAX2000S absolute maximum voltage for VCCA has been increased to 1.7V from 1.6V.

The following two figures give real examples of measured single event transients induced in low voltage drop out regulators when exposed to a heavy ion beam and how to apply the specification.  Note that the transients are not simple pulses.  A transient is outside of the specification if it is not contained in the rectangle defined above.

 


Figure 1. Transient goes outside of the rectangle and is "out of spec."


Figure 2. Transient stays within the rectangle and is "in spec."

References

  1. OLD News #18, "New FPGA Technologies: Currents, Voltages, and Temperatures," October 30, 2005.

  2. Microcircuit, Memory, Digital, CMOS, Field Programmable Gate Array, 2,000,000 Gates, Monolithic Silicon FSC: 5962, Revision: -, Dated: 5 April 2006 File name: 04221.pdf.

  3. Low Voltage Dropout Regulators and DC-DC Converters

  4. RTAX-S VCCA Guidelines Update, May 9, 2006

     

 

RTAX-S and AX Application Notes

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