AAT3201
150mA OmniPower™ LDO Linear Regulator
Higher input-to-output voltage differentials can be
Device Duty Cycle vs. VDROP
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.
(VOUT = 2.5V @ 25°C)
3.5
3
200mA
2.5
2
For example, an application requires VIN = 5.0V
while VOUT = 2.5V at a 150mA load and TA = 85°C.
VIN is greater than 4.28V, which is the maximum
safe continuous input level for VOUT = 2.5V at
150mA for TA = 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:
1.5
1
0.5
0
0
10
20
30
40
50
60
70
80
90
100
Duty Cycle (%)
IGND = 20µA
IOUT = 150mA
VIN = 5.0V
VOUT = 2.5V
Device Duty Cycle vs. VDROP
(VOUT = 2.5V @ 50°C)
3.5
3
200mA
2.5
2
PD(MAX)
(VIN - VOUT)IOUT + (VIN × IGND
150mA
%DC = 100
)
1.5
1
267mW
(5.0V - 2.5V)150mA + (5.0V × 20µA)
0.5
0
%DC = 100
0
10
20
30
40
50
60
70
80
90
100
%DC = 71.2%
Duty Cycle (%)
PD(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%.
Device Duty Cycle vs. VDROP
(VOUT = 2.5V @ 85°C)
The following family of curves shows the safe oper-
ating area for duty-cycled operation from ambient
room temperature to the maximum operating level.
3.5
3
100mA
2.5
2
200mA
150mA
1.5
1
0.5
0
0
10
20
30
40
50
60
70
80
90
100
Duty Cycle (%)
12
3201.2006.01.1.2
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
