We're learning about NVE's exclusive, True 8 millimeter creepage Isolators,with Tammy
in the NVE Application center. Tammy, give us the "truth" about isolator packages.
Creepage is the minimum spacing over insulation. Stringent rules are set by IEC60601.
Sixteen-pin wide-body SOICs are popular for isolators, but most don't meet
the eight-millimeter creepage requirement.
Why so, Tamarino?
With most packages, JEDEC tolerances, mold variability, and surface metal in the creepage
path means full 8 millimeter creepage can't be assured.
The shortest creepage path is usually around the end of the package.
Ordinary JEDEC wide-body packages are nominally 7.4 millimeters wide,
with approximately 8.1 millimeters between pins,
before subtracting tie bars.
I used to wear tie bars...
Well, these tie bars are tabs used in the molding process.
Internally connected or not,
the exposed metal reduces creepage. The tie bar subtraction, for an ordinary JEDEC package
is typically half a millimeter, bringing creepage to 7.4 to 7.6 millimeters.
That's not enough for 250 working volt applications,
even before tolerances.
So how are NVE True-8 packages, different?
Instead of a general-purpose package, we custom tooled the True 8 package.
It's within the JEDEC standard,
so there's no special board layout or handling.
It has much tighter tolerances for width and pin position.
And, rather than two metal tabs, the True 8 has just
one thin tab that secures the lead-frame during molding.
Creepage around the end is calculated
as the package edge width, plus two pin-to-end spacings, less the surface metal.
Even worst-case package dimensions and pin position,
the True 8 ensures 8.03 millimeters minimum creepage.
The path over the top is also specified for 8 millimeters.
Eliminating the outdated pin-one edge chamfer
ensures over-the-top creepage.
So, what parts come in the True 8 package?
There are oodles of True 8 parts:
high-performance IL700/200 Series Isolators,
single-chip transceivers,
cost-effective IL500s, and
IL600 Passive Input Isolators.
Common applications include serial busses,
SPI, A-D converters, and power interfaces.
Thanks, Tammy. How can viewers learn more about the True 8 package?
We have links to application bulletins, or call us at 800-GMR-7141, extension 4.