AAT3193 Datasheet, PDF (9/18 Pages) Advanced Analogic Technologies – 3-Channel Charge-Pump LED Driver

ChargePump^TM
Functional Block Diagram
C+ C–
Two-Mode
CP Control
IN
V_F Monitoring
PRODUCT DATASHEET
AAT3193
3-Channel Charge-Pump LED Driver
OUT
D1
D2
3
D3
EN/SET
(EN/PWM)
S²Cwire Control
(PWM Control)
I_REF
DAC
GND
RSET
Functional Description
The AAT3193 is a low-cost charge-pump solution designed
to drive up to three white LEDs. The charge pump oper-
ates from a 2.7V to 5.5V power source and converts it to
voltage levels necessary to drive the LEDs. LED current
is individually controlled through integrated current sinks
powered from the output of the charge pump. Low 1x
charge-pump output resistance and low-drop voltage
current sinks allow the charge pump to stay in 1x mode
with an input voltage as low as 3.75V and LED forward
voltages as high as 3.5V. Once in 2x mode, the charge
pump monitors the input supply voltage and automati-
cally switches back to 1x mode when there is sufficient
input voltage.
The AAT3193 requires only four external components:
one 1μF ceramic capacitor for the charge pump flying
capacitors (C_P), one 1μF ceramic input capacitor (C_IN),
one 1μF ceramic output capacitor (C_OUT) and a resistor
(R_SET) to set the maximum LED current. The three con-
stant current outputs of the AAT3193 (D1 to D3) can
drive three individual LEDs with a maximum current of
30mA each. AnalogicTech’s S²Cwire serial Interface
enables the AAT3193-1/-2/-3 and changes the current
sink magnitudes through the EN/SET pin. The AAT3193-4
uses an external PWM signal to enable the IC and control
the brightness of the LEDs.
Constant Current Control using R_SET
The maximum current is programmed by an external
resistor at the RSET pin. Using a 14.3kΩ external resis-
tor at the RSET pin, the AAT3193-1/-2/-4 includes an
integrated serial LED current control that sets the full-
scale LED current between 20mA and 0.63mA. For the
AAT3193-3, a 11.5kΩ external resistor at the RSET pin
sets the full-scale LED current between 20mA and
1.3mA. The full-scale LED current can set higher or lower
than 20mA; see Table 5. For maximum accuracy, a 1%
tolerance resistor is recommended.
3193.2008.07.1.3
www.analogictech.com
9