ZXLD1100 datasheet(9/16 Pages) DIODES

9 / 16 page

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 0.22 F 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.

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 1 F 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

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

Website

Murata

www.murata.com

Taiyo Yuden

www.t-yuden.com

Kemet

www.kement.com

AVX

www.avxcorp.com

ZXLD1100

SEMICO NDUC TORS

ISSUE 4 - JULY 2004

ZXLD1100 Datasheet(PDF) 9 Page - Diodes Incorporated

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