MC78LC00 Series
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8
APPLICATIONS INFORMATION
A typical application circuit for the MC78LC00 series is
shown in Figure 20.
Input Decoupling (C1)
A 0.1 mF capacitor either ceramic or tantalum is
recommended and should be connected close to the
MC78LC00 package. Higher values and lower ESR will
improve the overall line transient response.
Output Decoupling (C2)
The MC78LC00 is a stable component and does not
require any specific Equivalent Series Resistance (ESR) or
a minimum output current. Capacitors exhibiting ESRs
ranging from a few mW up to 3.0 W can thus safely be used.
The minimum decoupling value is 0.1 mF 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.
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 MC78LC00 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 MC78LC00 has 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
qJA
If junction temperature is not allowed above the
maximum 125°C, then the MC78LC00NTR can dissipate
up to 357 mW @ 25°C.
The power dissipated by the MC78LC00NTR can be
calculated from the following equation:
P
tot
+
ƪ
V
in
*I
gnd
(I
out
)
ƫ
)
[
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 1.1 mA. For an
MC78LC30NTR (3.0 V), the maximum input voltage will
then be 7.4 V.
V
out
C2
+
C1
+
Battery or
Unregulated
Voltage
Figure 20. Basic Application Circuit for NTR Suffixes
