NCP552, NCP553, NCV553
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7
APPLICATIONS INFORMATION
A typical application circuit for the NCP552 series and
NCP553 series is shown in Figure 1 and Figure 2, front page.
Input Decoupling (C1)
A 1.0 F capacitor either ceramic or tantalum is
recommended and should be connected close to the package.
Higher values and lower ESR will improve the overall line
transient response. If large line or load transients are not
expected, then it is possible to operate the regulator without
the use of a capacitor.
TDK capacitor: C2012X5R1C105K, or C1608X5R1A105K
Output Decoupling (C2)
The NCP552 and NCP553 are very stable regulators and
do not require any specific Equivalent Series Resistance
(ESR) or a minimum output current. If load transients are not
to be expected, then it is possible for the regulator to operate
with no output capacitor. Otherwise, capacitors exhibiting
ESRs ranging from a few m up to 10 can thus safely be
used. The minimum decoupling value is 0.1 F and can be
augmented to fulfill stringent load transient requirements.
The regulator accepts ceramic chip capacitors as well as
tantalum devices. Larger values improve noise rejection and
load regulation transient response.
TDK capacitor: C2012X5R1C105K, C1608X5R1A105K,
or C3216X7R1C105K
Enable Operation (NCP552 ONLY)
The enable pin will turn on the regulator when pulled high
and turn off the regulator when pulled low. These limits of
threshold are covered in the electrical specification section
of this data sheet. If the enable is not used then the pin should
be connected to V
in
.
Hints
Please be sure the Vin and GND lines are sufficiently
wide. When the impedance of these lines is high, there is a
chance to pick up noise or cause the regulator to
malfunction.
Set external components, especially the output capacitor,
as close as possible to the circuit, and make leads as short as
possible.
Thermal
As power across the NCP552 and NCP553 increases, it
might become necessary to provide some thermal relief. 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 also the
ambient temperature effect the rate of temperature rise for
the part. This is stating that when the devices have good
thermal conductivity through the PCB, the junction
temperature will be relatively low with high power
dissipation applications.
The maximum dissipation the package can handle is
given by:
PD
T
J(max)
T
A
R
JA
If junction temperature is not allowed above the
maximum 125°C, then the NCP552 and NCP553 can
dissipate up to 250 mW @ 25°C.
The power dissipated by the NCP552 and NCP553 can be
calculated from the following equation:
P
tot
[
V
in
*I
gnd
(I
out
)
]
[
V
in
V
out
]
*I
out
or
V
inMAX
P
tot
V
out
*
I
out
I
gnd
I
out
If an 80 mA output current is needed then the ground
current from the data sheet is 2.8 A. For an NCP552 or
NCP553 (3.0 V), the maximum input voltage will then be
6.12 V.
