AAT3200 Datasheet, PDF (12/16 Pages) Advanced Analogic Technologies – OmniPower LDO Linear Regulator

AAT3200
OmniPower™ LDO Linear Regulator
Higher input-to-output voltage differentials can be
obtained with the AAT3200, while maintaining
device functions in the thermal safe operating area.
To accomplish this, the device thermal resistance
must be reduced by increasing the heat sink area
or by operating the LDO regulator in a duty-cycled
mode.
For example, an application requires V_IN = 5.0V
while V_OUT = 3.0V at a 150mA load and T_A = 85°C.
V_IN is greater than 4.33V, which is the maximum
safe continuous input level for V_OUT = 3.0V at
150mA for T_A = 85°C. To maintain this high input
voltage and output current level, the LDO regulator
must be operated in a duty-cycled mode. Refer to
the following calculation for duty-cycle operation:
P_D(MAX) is assumed to be 200mW.
I_GND = 20µA
I_OUT = 150mA
V_IN = 5.0V
V_OUT = 3.0V
%DC =
100
P_D(MAX)
(V_IN - V_OUT)I_OUT + (V_IN × I_GND)
%DC =
100
200mW
(5.0V - 3.0V)150mA + (5.0V × 20µA)
%DC = 66.6%
For a 150mA output current and a 2.0V drop across
the AAT3200 at an ambient temperature of 85°C,
the maximum on-time duty cycle for the device
would be 66.6%.
The following family of curves shows the safe oper-
ating area for duty-cycled operation from ambient
room temperature to the maximum operating level.
Device Duty Cycle vs. V_DROP
(V_OUT = 2.5V @ 25°C)
3.5
3
2.5
2
1.5
1
0.5
0
0
200mA
150mA
10 20 30 40 50 60 70 80 90 100
Duty Cycle (%)
Device Duty Cycle vs. V_DROP
(V_OUT = 2.5V @ 50°C)
3.5
3
2.5
2
1.5
1
0.5
0
0
200mA
150mA
100mA
10 20 30 40 50 60 70 80 90 100
Duty Cycle (%)
Device Duty Cycle vs. V_DROP
(V_OUT = 2.5V @ 85°C)
3.5
3
2.5
2
1.5
1
0.5
0
0
100mA
50mA
200mA
150mA
10 20 30 40 50 60 70 80 90 100
Duty Cycle (%)
12
3200.2006.02.1.4