AAT3215IGV-2.8-T1 AAT [Advanced Analog Technology, Inc.], AAT3215IGV-2.8-T1 Datasheet - Page 11

• Manufacturer Part Number: AAT3215IGV-2.8-T1
• Description: 150mA CMOS High Performance LDO
• Manufacturer: AAT [Advanced Analog Technology, Inc.]

taining a reverse bias on the internal parasitic
diode.
should be avoided since this would forward bias
the internal parasitic diode and allow excessive
current flow into the V
the LDO regulator.
In applications where there is a possibility of V
exceeding V
mal operation, the use of a larger value C
tor is highly recommended. A larger value of C
with respect to C
rate during shutdown, thus preventing V
exceeding V
greater danger of V
periods of time, it is recommended to place a
Schottky diode across V
cathode to V
diode forward voltage should be less than 0.45V.
Thermal Considerations and High
Output Current Applications
The AAT3215 is designed to deliver a continuous
output load current of 150mA under normal operat-
ing conditions.
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 reg-
ulator is mounted on a printed circuit board utilizing
the minimum recommended footprint as stated in
the Layout Considerations section of this datasheet.
At any given ambient temperature (T
mum package power dissipation can be deter-
mined by the following equation:
Constants for the AAT3215 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
3215.2006.05.1.6
Conditions where V
IN
IN
IN
JA
P
.
for brief amounts of time during nor-
and anode to V
D(MAX)
OUT
In applications where there is a
= 190°C/W, the package thermal
OUT
=
will effect a slower C
OUT
exceeding V
T
IN
J(MAX)
to V
pin, possibly damaging
θ
OUT
JA
- T
OUT
OUT
might exceed V
A
J(MAX)
). The Schottky
(connecting the
IN
A
for extended
), the maxi-
, the maxi-
IN
OUT
IN
capaci-
decay
from
OUT
IN
IN
150mA CMOS High Performance LDO
where T
T
age power dissipation is 211mW. At T
maximum package power dissipation is 526mW.
The maximum continuous output current for the
AAT3215 is a function of the package power dissi-
pation and the input-to-output voltage drop across
the LDO regulator. Refer to the following simple
equation:
For example, if V
I
to exceed 264mA or if the ambient temperature
were to increase, the internal die temperature
would increase.
stant, the LDO regulator thermal protection circuit
would activate.
To determine the maximum input voltage for a
given load current, refer to the following equation.
This calculation accounts for the total power dissi-
pation of the LDO regulator, including that caused
by ground current.
This formula can be solved for V
maximum input voltage.
The following is an example for an AAT3215 set for
a 2.5 volt output:
V
I
I
V
From the discussion above, P
mined to equal 526mW at T
V
OUT(MAX)
OUT
GND
A
OUT
IN(MAX)
IN(MAX)
= 25°C. Given T
P
D(MAX)
= 2.5V
= 150mA
= 150µA
=
A
= 6.00V
< 264mA. If the output load current were
= 85°C, under normal ambient conditions
526mW + (2.5V
V
IN(MAX)
= (V
I
150mA + 150μA
OUT(MAX)
IN
=
IN
If the condition remained con-
= 5V, V
P
- V
A
D(MAX)
= 85°C, the maximum pack-
<
OUT
(V
I
OUT
OUT
)I
·
+ (V
IN
P
150mA)
OUT
A
D(MAX)
- V
+ I
= 25°C.
= 3V, and T
OUT
+ (V
OUT
GND
IN
D(MAX)
AAT3215
to determine the
·
)
I
IN
OUT
A
· I
= 25°C, the
)
was deter-
GND
A
= 25°C,
)
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