AAT3177 Datasheet, PDF (10/16 Pages) Advanced Analogic Technologies – High Current, High Efficiency Charge Pump with Auto-Timer

ChargePump^TM
PRODUCT DATASHEET
AAT3177
High Current, High Efficiency Charge Pump with Auto-Timer
Real-Time Control of the CT Pin
To achieve flash and torch mode control, the auto-timer
can be enabled or disabled in real-time. This can be done
by connecting a microcontroller or microprocessor GPIO
port to the CT pin.
To set up flash mode in real-time, enable the auto-timer
by tri-stating the GPIO port. Do not drive the port high. It
can only be set to high-impedance so that the CT capaci-
tor can be charged and discharged by the AAT3177.
To set up torch mode in real-time, disable the auto-
timer by driving the GPIO port low so that the CT pin will
be pulled to GND through the GPIO port.
AAT3177
EN/SET
Tri-state = TMR ON
Low = TMR OFF
CT
0.1μF = 1 sec
Figure 2: Enable or Disable the Auto-Timer in
Real-Time for Flash/Torch Control.
Flash/Torch Control Using the RSET Pin
An alternative method can be used for flash/torch con-
trol that eliminates the need to use the S²Cwire single-
wire interface. By using any typical digital I/O port, an
additional enable can be created (see Figure 3).
The I/O port output configuration can be an open-drain
NMOS or open-drain PMOS, but not a push-pull type. The
control will always act as an active-low flash enable or,
equivalently, an active-high torch enable (see Table 2).
EN
ENFL
Mode
0
0
Off
0
1
Off
1
0
Flash
1
1
Torch
Table 2: Flash/Torch Control Modes.
According to I/O port type, the following equations can
be used to calculate appropriate resistor values.
For an open-drain NMOS I/O port output configuration,
the line is pulled low to GND or left floating, according to
state. To calculate the appropriate R₁ and R₂ resistor
values, first calculate the R₁ resistor value needed for the
desired torch level LED current:
600mA · 187kΩ
R₁ = _{ILED (torch)}
2.7V
to 5.5V
C1
C2
1μF
1μF
C1+ C1- C2+ C2+
CIN
4.7μF
VOUT
AAT3177
EN
ENCT
C_T
EN/SET
CT
GND
F1
RSET
C_OUT
2.2μF
Flash
LED
R2
R1
ENF
Figure 3: Flash/Torch Control Using the RSET Pin.
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3177.2008.06.1.0