TS39300 TSC [Taiwan Semiconductor Company, Ltd], TS39300 Datasheet - Page 5

• Manufacturer Part Number: TS39300
• Description: 3A Ultra Low Dropout Positive Voltage Regulator
• Manufacturer: TSC [Taiwan Semiconductor Company, Ltd]

Application Information (continues)
Thermal Design
Linear regulators are simple to use. The most
complicated design parameters to consider are thermal
characteristics.
Thermal
design
requires
four
application-specific
parameters:
Maximum ambient temperature (Ta)
Output Current (Iout)
Output Voltage (Vout)
Input Voltage (Vin)
Ground Current (Ignd)
Calculate the power dissipation of the regulator from
these numbers and the device parameters from this
datasheet, where the ground current is taken from data
sheet.
Pd = (Vin – Vout) x Iout + Vin x Ignd
The heat sink thermal resistance is determined by:
Өsa = (Tj
– Ta) / Pd – (Өjc + Өcs)
(max)
o
o
Where Tj
≤ 125
C and Өcs is between 0
C and
(max)
o
2
C/W. The heat sink may by significantly reduced in
applications where the minimum input voltage is know
and is large compared with the dropout voltage and
distribute the heat between this resistor and the
regulator. The low dropout properties of vertical PNP
regulators allow significant reductions in regulator power
dissipation and the associated heat sink without
compromising performance. When this technique is
employed, a capacitor of at least 1.0uF is needed
directly between the input and regulator ground.
TS39300
5-6
2005/12 rev. A