Diodes AL3159 - Manual (Page 6)

AL3159
HIGH EFFICIENCY 1x/2x CHARGE PUMP
FOR WHITE LED APPLICATIONS
AL3159
Document number: DS35048 Rev. 2 - 2
6 of 10
www.diodes.com
January 2011
© Diodes Incorporated
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T
Functional Description
The AL3159 is a dual-mode high efficiency charge pump
(1x and 2x) device, driving nine LED channels with three
simple logic control inputs, intended for white
LED backlight applications. An internal comparator circuit
compares the voltage at each constant current sink input
against a reference voltage. To ensure maximum power
efficiency, the most appropriate switching mode (1x and
2x) is automatically selected.
The AL3159 requires only three external components: one
1 µF ceramic flying capacitor (C
1
) for the charge pump,
one 2.2µF ceramic input capacitor (C
IN
), and one
2.2µF ceramic charge pump output capacitor (C
OUT
).
The each output channel of the AL3159 can drive nine
individual LEDs with a maximum current of fixed
manufacture setting (20mA or 30mA) per channel. These
can be paralleled to give a total maximum output current of
270mA.
Disabled Current Sinks
Unused current channels must be disabled by connecting
the sinks to VOUT with only a small sense current flowing
through the disabled channel.
Soft-Start
Soft-start is incorporated to prevent excessive inrush
current during power-up, mode switching, and
transitioning out of stand-by mode.
Short-Circuit Protection
Short-circuit protection function is incorporated to prevent
excessive load current when either flying cap terminals or
output pin electrically tied to a very lower voltage or
ground.
Over-Voltage Protection
Over-Voltage Protection function is incorporated to limit
the output voltage under a safe value to avoid on-chip
device breakdown.
Under-Voltage Lockout
Under-Voltage lockout feature disables the device when
the input voltage drops below UVLO threshold.
Thermal Auto Shutdown
When the die temperature exceeds the thermal limit, the
device will be disabled and enter stand-by mode. The
operation resumes whenever the die cools off sufficiently.
CTL<3:1> LED ON/OFF CONTROL
000 ALL OFF
001 LED1~LED2 ON
010 LED3~LED5 ON
011 LED6~LED9 ON
100 LED9 ON
101 LED6~LED8 ON
110 LED1~LED5 ON
111 ALL ON