PRODUCT DATASHEET
AAT3113,AAT3114/14A
TM
ChargePump
High Efficiency 1.5X Fractional Charge Pumps For White LED Applications
Functional Block Diagram
VIN
Soft Start
C1+
C1-
1.5X
Charge
Pump
600kHz
Oscillator
C2+
C2-
Voltage
Reference
OUT
D1
D2
Current
Mode
DAC
5
8
S2Cwire
Interface
D3
32x8 bit
ROM
EN/SET
D4
D5*
D6*
GND
* AAT3114/14A only
the EN/SET pin and decodes them into 32 individual cur-
rent level settings each 1dB apart (see Table 1, Current
Level Settings). Code 32 is full scale, and Code 1 is full
scale attenuated by 31dB. The modulo 32 interface
wraps states back to state 1 after the 32nd clock. With
each EN/SET pulse, the output current increases by 1dB.
To decrease the output current by 1dB, 31 EN/SET clock
pulses are required. The counter can be clocked at
speeds up to 1MHz, so intermediate states are not visi-
ble. The first rising edge of EN/SET enables the IC and
initially sets the output LED current to -31dB, the lowest
setting equal to 525µA. Once the final clock cycle is input
for the desired brightness level, the EN/SET pin is held
high to maintain the device output current at the pro-
grammed level. The device is disabled 500µs after the
EN/SET pin transitions to a logic low state.
Functional Description
The AAT3113 and AAT3114/14A devices are high effi-
ciency 1.5X fractional charge pumps intended for white
LED backlight applications. The fractional charge pump
consists of a linear regulator followed by a 1.5X charge
pump. The AAT3113 and AAT3114/14A require only four
external components: two 1µF ceramic capacitors for the
charge pump flying capacitors (C1 and C2), one 1µF
ceramic capacitor for CIN, and one 0.33µF to 1µF ceram-
ic capacitor for COUT. The charge pump output is con-
verted into four or six constant current outputs (D1 to
D4 or D6) to drive four or six individual LEDs with a
maximum of 20mA each. The current source output
magnitude is controlled by the EN/SET serial data
S2Cwire interface. The interface records rising edges of
w w w . a n a l o g i c t e c h . c o m
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3113.2008.05.1.10
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