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FS8854
350mA LDO Linear Regulator
Fortune Semiconductor Corp.
TEL : +886-2-2809-4742
10/13
TD-0410025
Rev. 1.4
http://www.fsc.com.tw
FAX: +886-2-2809-4874
package is mounted on a double sided printed
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 FS8854 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