boost converter designed for driving Light Emitting
Diodes (LEDs) with constant current where the light
intensity is proportional to the current through them.
The input supply voltage range into the device (V
DD
)
is 2.6 to 4.6V. Operation of the driver at lower
voltages is possible as long as a 2.6鈥?.6V low-
current supply is available for the HV9903. The
device uses a single inductor and a minimum
number of passive components. The device can be
enabled/disabled via the SHDN pin.
The HV9903 has an internal oscillator. The oscillator
frequency is at fixed frequency of 1.2MHz that allows
use of small value inductors. The LED current can
be adjusted from 5 to 40mA by an external resistor
connected between the R
SET
and the GND pins. The
amount of current though the LED can also be
adjusted via DC voltage or a pulse width modulated
(PWM) signal to the R
SET
pin.
Soft-start is implemented on-chip, minimizing inrush
current to only 30% over steady state current.
An open LED circuit detects an open LED condition,
disables the driver, and sets the R
SET
pin high. The
driver is re-enabled by asserting SHDN low, then
high. If the open LED condition persists, the driver
will again latch off.
Applications
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Color LCD Backlighting
Cell phones, smart phones
PDAs, pocket PCs
Organizers
Digital Cameras
MP3 Players
Typical Application
Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate "products
liability indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined to be
defective due to workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product
specifications, refer to the Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current databook or to the Legal/Disclaimer
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