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FS8856
550mA LDO Linear Regulator
Fortune Semiconductor Co.
TEL : +886-2-2809-4742
10/13
TD-0405008
Rev. 1.3
http://www.fsc.com.tw
FAX: +886-2-2809-4874
circuit board with two square inches of copper
allocated for “heat spreading”, the resulting θJA is
180°C/W.
Based
on
a
maximum
operating
junction
temperature 125°C with an ambient of 25°C, the
maximum power dissipation will be:
() ()
W
T
T
P
CA
JC
A
J
MAX
555
.
0
180
25
125
=
−
=
+
−
=
θ
θ
Thermal characteristics were measured using a
double sided board with 1” x 2” square inches of
copper area connected to the GND pin for “heat
spreading”.
Input-Output Voltage
A regulator’s minimum input-output voltage differential,
or dropout voltage, determines the lowest usable
supply voltage. In battery-powered systems, this will
determine the useful end-of-life battery voltage. The
FS8856 uses a P-channel MOSFET pass transistor,
its dropout voltage is a function of drain-to-source
on-resistance (RDS(ON)) multiplied by the load current.
VDROPOUT = VIN-VOUT = RDS(ON) x IOUT