AAT3242 AAT, AAT3242 Datasheet - Page 12

• Manufacturer Part Number: AAT3242
• Description: Dual CMOS LDO Linear Regulator
• Manufacturer: AAT

Thermal Considerations and High
Output Current Applications
The AAT3242 is designed to deliver continuous
output load currents of 300mA and 150mA under
normal operations, and can supply up to 500mA
during circuit start-up conditions. This is desirable
for circuit applications where there might be a brief
high in-rush current during a power-on event.
The limiting characteristic for the maximum output
load current safe operating area is essentially
package power dissipation and the internal preset
thermal limit of the device. In order to obtain high
operating currents, careful device layout and circuit
operating conditions need to be taken into account.
The following discussions will assume the LDO
regulator is mounted on a printed circuit board uti-
lizing the minimum recommended footprint as stat-
ed in the layout considerations section of this doc-
ument. At any given ambient temperature (T
maximum package power dissipation can be deter-
mined by the following equation:
This formula can be solved for I
12
P
D(MAX)
= [(V
I
OUTA(MAX)
IN
- V
OUTA
OUTA
=
to determine the maximum output current for LDOA:
)I
P
300mA/150mA Dual CMOS LDO Linear Regulator
OUTA
D(MAX)
+ (V
A
), the
- (2×V
IN
x I
IN
GND
V
× I
IN
)] + [(V
GND
- V
Constants for the AAT3242 are T
mum junction temperature for the device, which is
125°C) and θ
resistance). Typically, maximum conditions are cal-
culated at the maximum operating temperature of T
= 85°C and under normal ambient conditions where
T
power dissipation is 364mW. At T
imum package power dissipation is 909mW.
The maximum continuous output current for the
AAT3242 is a function of the package power dissi-
pation and the input-to-output voltage drop across
the LDO regulator.
output current for a given output voltage, refer to
the following equation. This calculation accounts
for the total power dissipation of the LDO regulator,
including that caused by ground current.
) - (V
A
OUTA
= 25°C. Given T
IN
- V
IN
- V
OUTB
OUTB
)I
OUTB
JA
) × I
P
= 110°C/W (the package thermal
D(MAX)
+ (V
OUTB
A
= 85°C, the maximum package
To determine the maximum
IN
=
x I
T
J(MAX)
GND
θ
JA
)]
- T
A
AAT3242
A
= 25°C, the max-
J(MAX)
3242.2006.04.1.10
(the maxi-
A