ZXLD1100 데이터 시트보기 (PDF) - Zetex => Diodes
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ZXLD1100
Zetex => Diodes
ZXLD1100 Datasheet PDF : 16 Pages
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ZXLD1100
Open circuit protection
The voltage sense pin (VSENSE) can be connected to the
output to provide open circuit protection for the device
and external circuits when driving series connected
LEDs, thus eliminating the need for an external Zener
diode. Protection is provided by the internal avalanche
diode (ZD), which limits the maximum output voltage
to a value below the breakdown voltage of the output
switch when the connection to the diodes is broken.
Capacitor selection
A ceramic capacitor grounded close to the GND pin of
the package is recommended at the output of the
device. Surface mount types offer the best
performance due to their lower inductance. A
minimum value of 0.22F is advised, although higher
values will lower switching frequency and improve
efficiency especially at lower load currents. A higher
value will also minimize ripple when using the device
to provide an adjustable dc output current.
For maximum stability over temperature, capacitors
with X7R dielectric are recommended, as these have a
much smaller temperature coefficient than other types.
A table of recommended manufacturers is provided
below:
Manufacturer
Murata
Taiyo Yuden
Kemet
AVX
Website
www.murata.com
www.t-yuden.com
www.kement.com
www.avxcorp.com
A good quality, low ESR capacitor should also be used
for input decoupling, as the ESR of this capacitor is
effectively in series with the source impedance and
lowers overall efficiency. This capacitor has to supply
the relatively high peak current to the coil and smooth
the current ripple on the input supply. A minimum
value of 1F is acceptable if the input source is close to
the device, but higher values will improve performance
at lower input voltages, when the source impedance is
high. The input capacitor should be mounted as close
as possible to the IC
ISSUE 4 - JULY 2004
9
SEMICONDUCTORS
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