LDS8846 IXYS Corporation, LDS8846 Datasheet - Page 7

• Manufacturer Part Number: LDS8846
• Description: Lds8846 4-channel Ultra Low Dropout No Noise Led Driver
• Manufacturer: IXYS Corporation

LDS8846
Unused LED Channels
For applications with only two or three LEDs, unused
LED can be disabled via the appropriate CTRL pins
logic states. For applications requiring 1 LED only,
the unused LED pins should be tied to V
However, we recommend use of all channels
connecting
decreased current per channel. If one LED is used
only, current per channel should be decreased four
times, or this device may drive one LED with
maximum current up to 120 mA with all channels
connected in prallel and 30 mA current per chennel.
© 2009 IXYS Corp.
Characteristics subject to change without notice
Figure 3. Application circuit with three LEDs
Figure 4. Application circuit with two LEDs
Figure 5. Application circuit with two LEDs
them
in
parallel
with
accordingly
OUT
.
7
Protection Mode
The LDS8846 limits output current if V
shorted to ground either before or after device start.
This is to prevent the device from overload in case of
short circuit at the output. Device resumes normal
operation after short removed.
If the die temperature exceeds +150°C, the driver will
enter thermal protection shutdown mode. When the
device temperature drops by about 20°C, the device
resumes normal operation.
If the input voltage is below under-voltage protection
threshold, device turns into shutdown mode with high
impedance state at V
LED Selection
LEDs with forward voltages (V
4.5 V may be used. The device exhibits the highest
efficiency when V
voltage source is a Li-ion battery, we recommend
selecting LEDs with V
minimum expected battery discharging voltage to
extend the battery life and achieve highest efficiency.
If the minimum battery discharging voltage is limited
at 3 V, recommended V
2.95 V
External Components
The driver requires only one external component –
current setting resistor R
connected to the voltage source (battery) through
long traces, or voltage source has high electrical
noise due bad performance of other components
connected to this source, we recommend 1uF
decoupling capacitors
located as close to he device as possible.
Power dissipates on R
that allows use of very small surface mount
component.
Figure 5. Application circuit with one LED
F
OUT
voltage is close to V
SET
F
and all LED pins.
F
voltage is V
at the V
resistor is less then 100µW
SET
at least 50 mV below
Doc. No. 8846DS, Rev. N1.6
. However, if device is
F
) ranging from 1.3 V to
IN
F
and V
= 3.0 – 0.05 =
OUT
IN
OUT
. If the
pin is
pins