Frederick Jace
The Defense Supply Center Columbus, aka DSCC, is responsible for managing military specifications for electronic parts, like hybrid DC-DC Converters.
Hybrid packaged DC-DC Converters, which are several devices inside one large package, are controlled with several specifications, standards, and test methods.
The top-level specification is MIL-PRF-38534, which is used for almost all “hybridized” electronic parts.
This specification is quite complex and undergoes constant review and interpretation via Hybrid Manufacturers and other groups within the Industry or Government Solid State Devices Committee.
Why is MIL-PRF-38534 considered to be “top-level’’?
And what are the specifications NASA considers when categorizing DC-DC converters?
Let’s take a look at this information straight from NASA themselves!
1. What Is MIL-PRF-38534?
MIL-PRF-38534 follows a Qualified Manufacturer List (QML) approach, which focuses on the capacity and consistency of manufacturing processes and materials, plus a highly defined test flow.
This specification provides proof that the manufacturer used materials and processes that can withstand severe environmental stresses. Moreover, it also shows that the converter is electrically stable with long-term use.
After an audit of parts and successful testing for qualification, each part is awarded a QML Listing, which means it’s now qualified.
Sometimes the manufacturer might change process materials and methods of assembly. In this case, further testing followed by submission of results to DSCC is needed to reaffirm qualification.
2. What Are the Certification Classes of MIL-PRF-38534?
When DSCC audits the specific testing flows of production parts, it bases these audits on several certification classes.
There are five classes: K, H, G, D, and E.
In this part, we’ll focus on Class H and Class K.
Class H requirements form the baseline. Any extra pre-build inspections done by the manufacturer are awarded a Class K, in addition to Class H.
The extra requirements are intended to show a buyer that the parts are of high initial quality and that any defective pieces have been removed from the lot.
Moreover, Class K requirements address the special needs of space users.
NASA Goddard Space Flight Center (GSFC) policy affirms that Class H and K are the only classes routinely used in flight hardware. Plus, radiation hardness requires special DSCC approval and can be added to any class level.
If a user chooses to buy Class H or K DC-DC Converters, they must rely on the DSCC verification of the manufacturer’s systems.
However, if the user is still not convinced and wants further confirmation, they must do their own verification through consulting DSCC’s qualification team.
3. The Main Specifications for Mil-Grade DC-DC Converters
● Standard Microcircuit Drawings (SMDs)
These are Individual drawings created for particular devices in the MIL-PRF-38534 system. They include details of the individual converter, its package style, pin assignments, electrical performance specifications and ratings, temperature ratings, functional block diagrams, and specific application notes.
● Standard Microcircuit Cross-Reference Tool (SMCRT)
SMDs can be found by using the SMCRT tool, which has three main fields: left, middle, and right.
Set the left field to “Description,” the middle set to “Contains,” and set the right field to “DC-DC Converter.”
This gives you a list of about 1200 individual part numbers for all of the DC-DC Converters.
The MIL-PRF-38534/SMD system standardizes the part numbering system using the format below:
5962-0052201HXC or 5962R9161402KXA
- 5962 begins all SMDs and is the National Stock Class for microcircuits.
- The next letter identifies radiation tolerance ( the dash signifies “not rated”).
- The five digits, 00522 and 91614, identify the SMD drawing number.
- 02 and 01 identify device types when more than one is listed in one SMD.
- K, H, G, D, or E, identify the device class. The last digits are related to the package style and other physical details of the part.
Choose a Mil-Grade DC-DC Converter
Selecting a high-quality military DC-DC converter can be tough. That’s why it’s crucial to take your time in understanding the specifications by thoroughly examining the product’s datasheet or by reaching out to the companies themselves.
