1.5A Very L.D.O Voltage Regulator
LM27150/27151/27152
APPLICATION INFORMATION
The LM27150 are high performance low-dropout voltage regulators suitable for all moderate to high current
voltage regulator applications. Their 350mV dropout voltage at full load makes them especially valuable in
battery powered systems and as high efficiency noise filters in "post-regulator" applications. Unlike older
NPN-pass transistor designs, dropout performance of the PNP output of these devices is limited merely by
the low VCE saturation voltage.
The LM27150 family of regulators is fully protected from damage due to fault conditions. Current Limiting is
provided. This limiting is linear; output current under overload conditions is constant. Thermal shutdown
disables the device when the die temperature exceeds the 125℃ maximum safe operating temperature.
Transient protection allows device survival even when the input voltage spikes between -20V and +30V.
When the input voltage exceeds about 28V, the over voltage sensor temporarily disables the regulator.
VIN
VOUT
VIN
OUT
+
+
CIN
COUT
GND
Figure 1. Linear regulators require only two capacitors for operation.
Thermal Design
Linear regulators are simple to use. The most complicated design parameters to consider are thermal
characteristics. Thermal design requires the following application-specific parameters:
- Maximum ambient temperature, TA
- Output Current, IOUT
- Output Voltage, VOUT
- Input Voltage, VIN
First, we calculate the power dissipation of the regulator from these numbers and the device parameters
from this datasheet.
PD=IOUT(1.01VIN-VOUT
)
Where the ground current is approximated by 1% of IOUT. Then the heat sink thermal resistance is
determined with this formula:
T
- T
A
JMAX
(
)
θ
=
- θ +θ
SA
JC CS
P
D
θCS
Where TJMAX ≤ 125℃ and
is between 0 and 2℃/W.
Dec. 2011 – Rev.1.3.1
- 9 -
HTC
HTC [ HTC KOREA TAEJIN TECHNOLOGY CO. ]
