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Dropout 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 RS7110 use a P‐channel MOSFET
pass transistor, its dropout voltage is a function of drain‐to‐source on‐resistance R
DS(ON)
multiplied by the load current.
V
DROPOUT
=
V
IN
−
V
OUT
=
R
DS
(
ON
)
×
I
OUT
Application Note
Layout
a
b
c
d
e
f
g
h
i
Copper Area
Top Side (in )
Bottom Side (in
2
)
0
0
0
0.070
0
0.310
0.067
0.067
0.200
0.080
0.600
0.080
0.285
0.285
0.393
0.393
0.500
0.500
2
Thermal Area
SOT‐223 (θ
JA
,°C/W)
TO‐252 (θ
JA
,°C/W)
140
106
127
91
84
64
125
89
118
87
89
63
92
64
78
58
73
55
Top view of the PCB layout in real area.
Bottom view of the PCB layout in real area.
DS‐RS7110‐03
September, 2009
www.Orister.com
ORISTER [ ORISTER CORPORATION ]
