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Standard
light sources such as bulbs are replaced by LEDs or LED strings in
more and more applications now. The ASIC manufacturer PREMA
Semiconductor offers the new constant current driver PR4130
controlling up to three LEDs in series. Even if one or two LEDs are
disconnected or short circuited, the current and the brightness
remain constant, thus providing a high reliability.
The supply voltage of the PR4130 ranges from 10V up to 14.4V or a
maximum voltage of 21V for short time. Only one external resistor is
necessary for operation of the IC, which defines the LED current in
a range from 5mA up to 30mA. Due to the very accurate current
control the brightness of the LEDs is very constant and almost
independent of the supply voltage and the number of connected
LEDs.
The PR4130 circuit is compensating the disadvantage of serial LED
circuits, that a failure in one LED will lead to the disfunction of
the whole string. A Zener diode circuit provides a current flow also
with a break of one LED and together with the current control the
brightness of all connected LEDs stays smooth and constant also with
short circuit or break of one or two LEDs. The Zener diode circuit
has been defined for forward voltages of the LEDs of up to 2.3V.
PDF
Datasheet
Due to the supply voltage of around 12V the
PR4130 is well suited for automotive applications such as a driver
for the third high mounted stop light (Center High Mount Stop Light)
consisting of a string of more LEDs. In this case several PR4130 can
be used in parallel, uniformly distributed current is guaranteed by
the current control also at a failure of a single LED. Further
applications are decoration light strings with 12V power supplies.
The PR4130 is offered as a standard cell for design of an analog
ASIC. Production of a custom specific standard cell IC can be
reasonable for annual amounts from several 10 k units. The NRE cost
are comparatively low and possible customised adaptions are often
quickly implemented.
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