Datasheet

ESD Protection
We have learned before that the ACULED is a highly sophisticated semiconductor product
which is sensitive to electro-static discharge (ESD). Though all LED chips are generally
sensitive to ESD, some chips are even more sensitive than others. Therefore Excelitas
protects the most sensitive chips with ESD protection diodes up to 2 kV according to the circuit
diagram in figure 23. Please refer to the specific datasheet to check whether your ACULED VHL
has ESD protection or not. Figure 24 shows the layout with and without these diodes according
to the datasheet. Generally speaking UV, blue, green and white LEDs made from InGaN are the
most ESD sensitive chips. When you design your own ACULED you can choose if you want to
use ESD protection or not. In doubt, please ask Excelitas if ESD protection is recommended
or not. If protection diodes are used, they are always at all four channels.
LED
Figure 23
Circuit diagram of the ACULED
+
-
Z-diode and LED chip.
Z-Diode
Figure 24
Layout of the ACULED VHL / DYO
with (left) and without (right)
Z-diodes.
Electrostatic damage to electronic devices can occur at any point from manufacture to field
service. Damage results from handling the ACULED in uncontrolled surroundings without
adequate ESD control practices. Static charges of 2 kV are not uncommon and can be
generated quite easily. In comparison, a discharge of only 10 V can destroy a Class 1 ESD
sensitive chip like InGaN dies that are widely used with the ACULED VHL. ESD damaged
ACULED LEDs can appear dim, dead, shorted, or with low forward voltage.
The ESD protection diodes used with the ACULED are bidirectional Zener diodes (Z-diodes) on
chip level that are placed close to the LED chips inside the encapsulation ring. The dies are very
small and do not disturb the light distribution of the LEDs. With a reverse leakage current of less
than 1 µA at a reverse voltage of 5 V they also do not influence the electrical operation of the
LEDs. The reverse break through voltage (also known as Zener voltage V
Z
) is 8 V ± 1 V at
10 mA. If the voltage is higher than V
Z
- for example at electro-static discharge or too high
www.excelitas.com Driving the ACULED® VHL™ 21