AAT3201 Datasheet, PDF (12/15 Pages) Advanced Analogic Technologies – 150mA OmniPower LDO Linear Regulator

AAT3201
150mA OmniPower™ LDO Linear Regulator
Higher input-to-output voltage differentials can be
obtained with the AAT3201, 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 = 2.5V at a 150mA load and T_A = 85°C.
V_IN is greater than 4.28V, which is the maximum
safe continuous input level for V_OUT = 2.5V 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:
I_GND = 20µA
I_OUT = 150mA
V_IN = 5.0V
V_OUT = 2.5V
%DC = 100
P_D(MAX)
(V_IN - V_OUT)I_OUT + (V_IN × I_GND)
%DC = 100
267mW
(5.0V - 2.5V)150mA + (5.0V × 20µA)
%DC = 71.2%
P_D(MAX) was assumed to be 267mW.
For a 150mA output current and a 2.5V drop across
the AAT3201 at an ambient temperature of 85°C,
the maximum on-time duty cycle for the device
would be 71.2%.
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
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
200mA
2
150mA
1.5
1
0.5
0
0
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
100mA
2.5
2
200mA
1.5
1
150mA
0.5
0
0 10 20 30 40 50 60 70 80 90 100
Duty Cycle (%)
12
3201.2006.01.1.2