1.5A Very L.D.O Voltage Regulator
LM29150/1/2/3
Applications Information
The LM29150 are high performance low-dropout voltage regulators suitable for all moderate to high
-current voltage regulator applications. Their 350mV dropout voltage at full load make 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 LM29150 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 +60V. When the input voltage exceeds about 35V to 40V. The over
voltage sensor temporarily disables the regulator.
Figure 3. 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, T
A
*
Output Current, I
OUT
*
Output Voltage, V
OUT
*
Input Voltage, V
IN
First, we calculate the power dissipation of the regulator from these numbers and the device
parameters from this datasheet.
P
D
=I
OUT
(1.01V
IN
-V
OUT
)
Where the ground current is approximated by 1% of I
OUT
. Then the heat sink thermal
resistance is determined with this formula:
Where TJ MAX≤ 125℃ and ΘCS is between 0 and 2℃/W.
Capaitor Requirements
For stability and minimum output noise,a capacitor on the regulator output is necessary. The
value of this capacitor is dependent upon the output current; lower currents allow smaller
capcitors. LM29150 regulators are stable with the 10uF minimum capacitor values at full load.
Where the regulator is powered from a source with a high AC impedance, a 0.1uF capacitor
connected between input and GND is recommended. This capacitor should have good
characteristics to above 250kHz.
Mar. 2006-Rev06
97
HTC
HTC [ HTC KOREA TAEJIN TECHNOLOGY CO. ]
