AAT3113, AAT3114/14A
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
OUT
Reference
D1
D2
D3
D4
Current
Mode
DAC
5
8
S2Cwire
EN/SET
32x8 bit
ROM
Interface
D5*
D6*
GND
* AAT3114/14A only
and decodes them into 32 individual current 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 visible.
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 out-
put current at the programmed 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
efficiency 1.5X fractional charge pumps intended
for white LED backlight applications. The fraction-
al charge pump consists of a linear regulator fol-
lowed by a 1.5X charge pump. The AAT3113 and
AAT3114/14A require only four external compo-
nents: 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
ceramic capacitor for COUT. The charge pump out-
put is converted into four or six constant current
outputs (D1 to D4 or D6) to drive four or six indi-
vidual 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 the EN/SET pin
8
3113.2006.07.1.9
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
