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參數(shù)資料
| 型號(hào)： | AAT3218IJS-1.25-T1 |
| 廠商： | Advanced Analog Technology,lnc. |
| 英文描述： | 150mA MicroPower⑩ High Performance LDO |
| 中文描述： | 150mA的微功耗高性能的LDO⑩ |
| 文件頁(yè)數(shù)： | 11/18頁(yè) |
| 文件大?。?/td> | 384K |
| 代理商： | AAT3218IJS-1.25-T1 |
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No-Load Stability
The AAT3218 is designed to maintain output volt-
age regulation and stability under operational no-
load conditions. This is an important characteristic
for applications where the output current may drop
to zero.
Reverse Output-to-Input Voltage
Conditions and Protection
Under normal operating conditions, a parasitic
diode exists between the output and input of the
LDO regulator. The input voltage should always
remain greater than the output load voltage, main-
taining a reverse bias on the internal parasitic
diode. Conditions where V
OUT
might exceed V
IN
should be avoided since this would forward bias
the internal parasitic diode and allow excessive
current flow into the V
OUT
pin, possibly damaging
the LDO regulator.
In applications where there is a possibility of V
OUT
exceeding V
IN
for brief amounts of time during nor-
mal operation, the use of a larger value C
IN
capaci-
tor is highly recommended. A larger value of C
IN
with respect to C
OUT
will effect a slower C
IN
decay
rate during shutdown, thus preventing V
OUT
from
exceeding V
IN
. In applications where there is a
greater danger of V
OUT
exceeding V
IN
for extended
periods of time, it is recommended to place a
Schottky diode across V
IN
to V
OUT
(connecting the
cathode to V
IN
and anode to V
OUT
). The Schottky
diode forward voltage should be less than 0.45V.
Thermal Considerations and High
Output Current Applications
The AAT3218 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 must 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
A
), the maxi-
mum package power dissipation can be deter-
mined by the following equation:
Constants for the AAT3218 are T
J(MAX)
, the maxi-
mum junction temperature for the device which is
125°C and
Θ
JA
= 190°C/W, the package thermal
resistance. Typically, maximum conditions are cal-
culated at the maximum operating temperature
where T
A
= 85°C, under normal ambient conditions
T
A
= 25°C. Given T
A
= 85°C, the maximum pack-
age power dissipation is 211mW. At T
A
= 25°C, the
maximum package power dissipation is 526mW.
The maximum continuous output current for the
AAT3218 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
IN
= 5V, V
OUT
= 3V, and T
A
= 25°C,
I
OUT(MAX)
< 264mA. If the output load current were
to exceed 264mA or if the ambient temperature
were to increase, the internal die temperature
would increase. If the condition remained con-
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.
P
D(MAX)
= (V
IN
- V
OUT
)I
OUT
+ (V
IN
x I
GND
)
P
D(MAX)
I
OUT(MAX)
<(V
IN
- V
OUT
)
[T
J(MAX)
- T
A
]
JA
P
D(MAX)
=
AAT3218
150mA MicroPower High Performance LDO
3218.2006.04.1.8
11
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| AAT3218IJS-2.6-T1 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:150mA MicroPower⑩ High Performance LDO |
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