IS31BL3212
Integrated Silicon Solution, Inc. – www.issi.com 7
Rev. C, 06/24/2014
LED SELECTION
The IS31BL3212 has low headroom voltage and it is
designed to drive white-LEDs.
The drive current will automatically scale down to
reduce the LED current consumption.
INPUT CAPACITOR SELECTION
The IS31BL3212 is designed to run off of a fixed input
voltage. Depending on the stability and condition of
this voltage rail, it may be necessary to add a small
input capacitor to help filter out any noise that may be
present on the line. In the event that filtering is needed,
ceramic composition capacitors are highly recom-
mended over all other types of capacitors for use with
the IS31BL3212. Ceramic capacitors offer many
advantages over their tantalum and aluminum
electrolytic counterparts. A ceramic capacitor typically
has very low ESR, is lowest cost, has a smaller PCB
footprint, and is non-polarized. Low ESR ceramic
capacitors help to maximize charge pump transient
response. Since ceramic capacitors are non-polarized,
they are not prone to incorrect connection damage.
THERMAL PROTECTION
The IS31BL3212 has a thermal protection circuit that
will shut down the chip if the die temperature rises
above the thermal limit.
Although the IS31BL3212 is designed for driving white
LEDs, the device also can be used to drive most types
of LEDs with forward voltage specifications ranging
from 2.0V to 4.7V. LED applications may include main
and sub-LCD display backlighting, camera photo-flash
applications, color (RGB) LEDs, infrared (IR) diodes
for remotes, and other loads benefiting from a
controlled output current generated from a varying
input voltage. Since the D1 to D4 output current
sources are matched with negligible voltage
dependence, the LED brightness will be matched
regardless of the specific LED forward voltage (V
F
)
levels. In some instances (e.g., in high luminous output
applications such as photo flash), it may be necessary
to drive high-V
F
type LEDs. The low dropout current
sources in the IS31BL3212 make it capable of driving
LEDs with forward voltages as high as 4.7V at full
current from an input supply of 2.7V to 5.0V. Outputs
can be paralleled to drive high-current LEDs without
complication
