MALVERN, Pa.--(BUSINESS WIRE)--
Vishay Precision Group, Inc. (NYSE: VPG) today announced that it has
completed tests showing that its Bulk Metal® Foil current
sensing resistors meet the accuracy and stability required by its
aircraft customers for charging of Li-ion batteries in avionics
applications. VFR resistors provide a variety of device configurations
and ultra-high-precision specifications to help ensure the efficient and
safe charging of Li-ion batteries. They include the surface-mount Z-Foil
VCS1610Z and VCS1625ZP and the high-power VCS331Z and CSNG (offering 3-
or 6-chip constructions).
The Li-ion battery charging process goes through several critical phases
to ensure the battery is charged to its maximum capacity, while at the
same time following certain safety rules to avoid explosion or fire.
Li-ion battery chargers require accurate current and voltage settings
and monitoring, as well as a constant current and constant voltage. If
these accuracy requirements are not met, the charger will undercharge or
overcharge the battery. A failure to completely charge the battery
results in reduced battery life, while overcharging can cause batteries
to fail due to overheating.
Precision current sensing resistors are required to charge and monitor
the Li-ion battery at a known current level until it reaches its final
voltage. At this point, the charger circuitry switches over to constant
voltage mode, providing the current necessary to hold the battery at
this final voltage. For both phases, Bulk Metal Foil resistors provide
higher accuracy than other technologies, such as thin film, thick film,
and wirewound resistors.
“Li-ion batteries are well established in portable consumer electronics
and are now becoming more popular in military and advanced civilian
avionics. As the scope of their applications has expanded, so have the
stringent requirements they must meet, especially in terms of cell
safety and lifetime. For designers, the main challenge in meeting these
requirements is in finding the optimal point between undercharging and
overcharging through continuous accurate and stable monitoring of input
and output current,” said Yuval Hernik, senior director of application
engineering for VFR.
Hernik added, “The need for safety was emphasized in the latest
near-catastrophic incident involving the charging of Li-ion batteries,
in which a Dreamliner caught fire while parked at Heathrow. Luckily, no
passengers were on board. In our opinion, designers in the avionics
industry have every motivation to look for more precise and reliable
commercial-off-the-shelf (COTS) resistors to accurately monitor the
battery voltage when connected to the charger. Bulk Metal Foil current
sensing resistors provide the low TCR and thermal EMF required to meet
this need. They also provide wide resistance ranges, and unlike most
COTS resistors, any resistance value within their given range is
available with no additional cost or lead time effect.”
There are five important phases that need to be considered when choosing
a current sense or shunt resistor for any application: connection
errors, external and Internal temperature errors, frequency, drift over
time, load life stability and thermal EMF. VFR's Bulk Metal Foil current
sense resistors offer a four-terminal Kelvin connection for increased
accuracy. They feature an ultra-low TCR of ±0.05 ppm/°C typical (0°C to
+60°C) and ±0.2 ppm/°C typical (-55°C to +125°C, +25°C ref.). The
surface-mount VCS1610Z and VCS1625ZP offer load-life stability of
±0.015% at 70°C for 2,000 hours at rated power while the VCS331Z power
resistor features load-life stability down to ±0.005% (50 ppm) typical
at 3 W and +25°C for 2,000 hours (mounted on a heatsink) and thermal EMF
of 0.05 μV/°C typical.
Featuring a non-inductive (<0.08 μH), non-capacitive design, Bulk Metal
Foil resistors offer a rise time of 1.0 ns with effectively no ringing,
a thermal stabilization time of < 1 s to within 10 ppm of steady state
value, current noise of 0.010 µVrms per volt of applied voltage (<-40
dB), voltage coefficient of <0.1 ppm/V, and resistance tolerance down to
±0.01%.
Samples and production quantities of the Z-Foil resistors are available
now, with lead times of five days for prototype samples and from two
days to five weeks for standard orders at the catalog houses, depending
on their shelf availability.
Further information about Vishay Foil Resistors products is available at www.vishayfoilresistors.com.
Follow Vishay Foil Resistors at http://twitter.com/foilresistor.
About Vishay Precision Group
Vishay Precision Group (VPG) is an internationally recognized designer,
manufacturer and marketer of: components based on its resistive foil
technology; sensors; and sensor-based systems specializing in the
growing markets of stress, force, weight, pressure, and current
measurements. VPG is a market leader of Foil Technology Products,
providing ongoing technology innovations in precision foil resistors and
foil strain gages, which are the foundation of the Company’s Force
Sensors Products and its Weighing and Control Systems. The product
portfolio consists of a variety of well-established brand names
recognized for precision and quality in the marketplace. To learn more,
visit VPG at www.vishaypg.com.
About VPG Foil Resistors
VPG Foil Resistors, a part of Vishay Precision Group (VPG), produces the
most precise and stable resistors available. Distinguished by the
premier brands Vishay Foil Resistors, Powertron, and Alpha Electronics,
the VPG Foil Resistors portfolio includes discrete resistors and
resistor networks in surface mount and through-hole (fixed-lead)
configurations; customized chip resistor networks; precision trimming
potentiometers; and discrete chips for use in hybrid circuits. These
devices are used in applications requiring a high degree of precision
and stability, such as in medical testing equipment, semiconductor
equipment, precision measuring instruments, aerospace, and military
applications. To learn more, visit www.vishayfoilresistors.com.
Bulk Metal is a registered trademark of Vishay Precision Group, Inc.
Links to featured product datasheets:
http://www.vishaypg.com/ppg?63226
(VCS1610Z)
http://www.vishaypg.com/ppg?63155
(VCS1625ZP)
http://www.vishaypg.com/ppg?63240
(VCS331Z, CSNG et al)
Link to product image:
http://www.flickr.com/photos/[email protected]/9606240631/sizes/l/in/photostream/
Vishay Precision Group, Inc.
Marti Spalding, +1 919-374-5515
Director,
Global MarCom
[email protected]
Source: Vishay Precision Group, Inc.