AAT3215
150mA CMOS High Performance LDO
Applications Information
Device Duty Cycle vs. VDROP
VOUT = 2.5V @ 25 C
VOUT = 2.5 volts
IOUT = 150mA
IGND = 150uA
3.5
3
2.5
VIN(MAX)=(211mW+(2.5Vx150mA))/(150mA +150uA)
VIN(MAX) = 3.90V
200mA
2
1.5
1
Higher input to output voltage differentials can be
obtained with the AAT3215, while maintaining
device functions within 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.
0.5
0
0
10
20
30
40
50
60
70
80
90
100
Duty Cycle (%)
For example, an application requires VIN = 4.2V
while VOUT = 2.5V at a 150mA load and TA = 85°C.
VIN is greater than 3.90V, 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:
Device Duty Cycle vs. VDROP
VOUT= 2.5V @ 50 C
3.5
3
2.5
2
200mA
1.5
1
150mA
PD(MAX) is assumed to be 211mW
0.5
0
IGND = 150µA
IOUT = 150mA
VIN = 4.2 volts
0
10
20
30
40
50
60
70
80
90
100
Duty Cycle (%)
VOUT = 2.5 volt
ꢀDC=100(PD(MAX)/((VIN-VOUT)IOUT+(VINxIGND))
ꢀDC=100(211mW/((4.2V-2.5V)150mA+(4.2Vx150µA))
ꢀDC = 85.54ꢀ
Device Duty Cycle vs. VDROP
VOUT = 2.5V @ 85 C
For a 150mA output current and a 2.7volt drop
across the AAT3215 at an ambient temperature of
85°C, the maximum on time duty cycle for the
device would be 85.54ꢀ.
3.5
3
100mA
2.5
2
200mA
150mA
The following family of curves show the safe oper-
ating area for duty cycled operation from ambient
room temperature to the maximum operating level.
1.5
1
0.5
0
0
10
20
30
40
50
60
70
80
90
100
Duty Cycle (%)
3215.2002.03.0.91
11
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
