Datasheet

depends on the particular circuit. Remember that voltages have to be added in serial circuits
and remain the same in parallel connection, whereas currents have to be calculated vice versa.
Figure 8
Circuit diagram of
cascaded ACULEDs.
The corresponding
chips of each color
are connected
serially.
ACULED 1 ACULED 2 ACULED 3 ACULED 4 ACULED 5 ACULED 6 ACULED 7 ACULED 8
Figure 9
Mixture of parallel
and serial connection
of one ACULED
channel to decrease
ACULED 9 ACULED 10 ACULED 11 ACULED 12 ACULED 13 ACULED 14 ACULED 15 ACULED 16
V F sum and increase
redundancy.
Testing in laboratory
There is a significant danger of destroying LED chips when testing them, for example in a
laboratory environment. Beside the above mentioned issues of ESD and current overshoot of
faulty drivers and PSUs, bad connections, for example with improperly soldered cables, can
damage a chip due to the peak caused by a sudden circuitry interrupt. Make sure you have
switched off the PSU any time you connect or disconnect the ACULED to it. When testing an LED
with a constant current source, use a voltage limit to avoid voltage overshoot. In doubt you can start
with a small voltage and increase it carefully to the value of the maximum forward voltage that is
shown in the ACULED datasheet.
Influence of Current
As described in the previous chapter, LEDs are usually driven by current. Hence a constant LED
light output requires a constant current source. Beside the necessity to avoid the chip from
being damaged by overdriving, the current has an impact on several parameters which are
particularly
• lifetime [t
Life
]
• forward voltage [V
F
]
www.excelitas.com Driving the ACULED® VHL™ 9