AAT3236IGV-2.8-T1 AAT [Advanced Analog Technology, Inc.], AAT3236IGV-2.8-T1 Datasheet - Page 11

• Manufacturer Part Number: AAT3236IGV-2.8-T1
• Description: 300mA CMOS High Performance LDO
• Manufacturer: AAT [Advanced Analog Technology, Inc.]

Reverse Output-to-Input Voltage
Conditions and Protection
Under normal operating conditions, a parasitic diode
exists between the output and input of the LDO reg-
ulator.
greater than the output load voltage, maintaining a
reverse bias on the internal parasitic diode.
Conditions where V
avoided since this would forward bias the internal
parasitic diode and allow excessive current flow into
the V
In applications where there is a possibility of V
exceeding V
mal operation, the use of a larger value C
itor 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 AAT3236 is designed to deliver a continuous
output load current of 300mA under normal opera-
tions and can supply up to 500mA during circuit
start-up conditions.
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 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:
3236.2007.03.1.4
OUT
The input voltage should always remain
pin, possibly damaging the LDO regulator.
IN
IN
IN
.
for brief amounts of time during nor-
and anode to V
OUT
In applications where there is a
OUT
OUT
will effect a slower C
This is desirable for circuit
might exceed V
exceeding V
IN
to V
OUT
OUT
). The Schottky
(connecting the
IN
A
for extended
IN
), the maxi-
should be
IN
OUT
IN
capac-
decay
from
OUT
IN
300mA CMOS High Performance LDO
Constants for the AAT3236 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
where T
T
age power dissipation is 211mW. At T
maximum package power dissipation is 526mW.
The maximum continuous output current for the
AAT3236 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
25°C, I
were to exceed 584mA or if the ambient tempera-
ture 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 AAT3236 set for
a 3.0V output:
A
= 25°C. Given T
P
OUT(MAX)
D(MAX)
A
= 85°C, under normal ambient conditions
V
IN(MAX)
= (V
JA
I
< 584mA. If the output load current
P
OUT(MAX)
D(MAX)
=
= 190°C/W, the package thermal
IN
IN
If the condition remained con-
P
= 4.2V, V
- V
A
D(MAX)
= 85°C, the maximum pack-
=
OUT
<
I
T
OUT
V
J(MAX)
)I
+ (V
P
IN
OUT
θ
+ I
D(MAX)
- V
OUT
JA
OUT
- T
GND
+ (V
OUT
IN
AAT3236
= 3.3V, and T
A
J(MAX)
to determine the
× I
IN
OUT
A
x I
= 25°C, the
, the maxi-
)
GND
)
A
11
=