AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
600mA · 187kΩ
ILED (torch)
EN
ENFL
Mode
R1 =
0
0
1
1
0
1
0
1
Off
Off
Next, choose R2 based on the desired flash level
LED current:
Flash
Torch
Table 2: Flash/Torch Control Modes.
R1 · 600mA · 187kΩ
R1 · ILED (flash) - 600mA · 187kΩ
R2 =
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 configu-
ration, 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 resis-
tor value needed for the desired torch level LED
current:
The current and resistance values used in the equa-
tions come from the conditions placed on the IDX
parameter of the Electrical Characteristics table.
C1
1µF
C2
1µF
C1+
C1- C2+
C2+
2.7V
to 5.5V
VOUT
CIN
4.7µF
COUT
2.2µF
Flash
LED
AAT3171
EN
EN/SET
CT
F1
R2
ENCT
RSET
ENFL
GND
CT
R1
Figure 3: Flash/Torch Control Using the RSET Pin.
3171.2007.03.1.1
11
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
