MC78LC00 Series

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9

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 m

Ω 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

+

TJ(max) * TA

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:

Ptot + [Vin *Ignd (Iout)] ) [Vin * Vout] *Iout

or

VinMAX +

Ptot ) Vout * Iout

Ignd ) Iout

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.

C2

+

C1

+

Battery or

Unregulated

Voltage

Figure 20. Basic Application Circuit for NTR Suffixes