NCP718
www.onsemi.com
6
APPLICATIONS INFORMATION
The NCP718 is the member of new family of Wide Input
Voltage Range Low Dropout Regulators which delivers
Ultra Low Ground Current consumption, Good Noise and
Power Supply Rejection Ratio Performance. The NCP718
incorporates EN pin and soft−start feature for simple
controlling by microprocessor or logic.
Input Decoupling (C
IN
)
It is recommended to connect at least 1 mF ceramic X5R
or X7R capacitor between IN and GND pin of the device.
This capacitor will provide a low impedance path for any
unwanted AC signals or noise superimposed onto constant
input voltage. The good input capacitor will limit the
influence of input trace inductances and source resistance
during sudden load current changes.
Higher capacitance and lower ESR capacitors will
improve the overall line transient response.
Output Decoupling (C
OUT
)
The NCP718 does not require a minimum Equivalent
Series Resistance (ESR) for the output capacitor. The device
is designed to be stable with standard ceramics capacitors
with values of 1 mF or greater. The X5R and X7R types have
the lowest capacitance variations over temperature thus they
are recommended.
Power Dissipation and Heat Sinking
The maximum power dissipation supported by the device
is dependent upon board design and layout. Mounting pad
configuration on the PCB, the board material, and the
ambient temperature affect the rate of junction temperature
rise for the part. For reliable operation junction temperature
should be limited to +125°C.
The maximum power dissipation the NCP718 can handle
is given by:
P
D(MAX)
+
ƪ
T
J(MAX)
* T
A
ƫ
R
qJA
(eq. 1)
The power dissipated by the NCP718 for given
application conditions can be calculated from the following
equations:
P
D
[ V
IN
ǒ
I
GND
(I
OUT
)
Ǔ
) I
OUT
ǒ
V
IN
* V
OUT
Ǔ
(eq. 2)
or
V
IN(MAX)
[
P
D(MAX)
)
ǒ
V
OUT
I
OUT
Ǔ
I
OUT
) I
GND
(eq. 3)
Hints
VIN and GND printed circuit board traces should be as
wide as possible. When the impedance of these traces is
high, there is a chance to pick up noise or cause the regulator
to malfunction. Place external components, especially the
output capacitor, as close as possible to the NCP718, and
make traces as short as possible.
