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AAT3216 Datasheet, PDF (11/16 Pages) List of Unclassifed Manufacturers – 150mA MicroPower™ LDO with PowerOK
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AAT3216
150mA MicroPower™ LDO with PowerOK
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 document.
At any given ambient temperature (TA), the maxi-
mum package power dissipation can be deter-
mined by the following equation:
PD(MAX)
=
TJ(MAX) -
θJA
TA
Constants for the AAT3216 are TJ(MAX), the maxi-
mum junction temperature for the device which is
125°C, and ΘJA = 190°C/W, the package thermal
resistance. Typically, maximum conditions are cal-
culated at the maximum operating temperature
where TA = 85°C, under normal ambient conditions
TA = 25°C. Given TA = 85°C, the maximum pack-
age power dissipation is 211mW. At TA = 25°C, the
maximum package power dissipation is 526mW.
The maximum continuous output current for the
AAT3216 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:
IOUT(MAX) <
PD(MAX)
VIN - VOUT
For example, if VIN = 5V, VOUT = 3V, and TA = 25°C,
IOUT(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.
PD(MAX) = (VIN - VOUT)IOUT + (VIN x IGND)
This formula can be solved for VIN to determine the
maximum input voltage.
3216.2006.01.1.3
VIN(MAX) =
PD(MAX) + (VOUT × IOUT)
IOUT + IGND
The following is an example for an AAT3216 set for
a 2.5V output:
VOUT = 2.5V
IOUT = 150mA
IGND = 150µA
526mW + (2.5V × 150mA)
VIN(MAX) =
150mA + 150µA
VIN(MAX) = 6.00V
From the discussion above, PD(MAX) was deter-
mined to equal 526mW at TA = 25°C.
Thus, the AAT3216 can sustain a constant 2.5V out-
put at a 150mA load current as long as VIN is ≤ 6.00V
at an ambient temperature of 25°C. 6.0V is the
absolute maximum voltage where an AAT3216
would never be operated, thus at 25°C, the device
would not have any thermal concerns or operational
VIN(MAX) limits.
This situation can be different at 85°C. The follow-
ing is an example for an AAT3216 set for a 2.5V
output at 85°C:
VOUT = 2.5V
IOUT = 150mA
IGND = 150µA
211mW + (2.5V × 150mA)
VIN(MAX) =
150mA + 150µA
VIN(MAX) = 3.90V
From the discussion above, PD(MAX) was deter-
mined to equal 211mW at TA = 85°C.
Higher input-to-output voltage differentials can be
obtained with the AAT3216, while maintaining
device functions within the thermal safe operating
area. To accomplish this, the device thermal
resistance must be reduced by increasing the heat
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