APPLICATION NOTES

HEAT SINK SELECTION:

To select a heat sink for the MSK5102, the following formula for

convective heat flow may be used.

Governing Equation:

WHERE:

Tj = Junction Temperature

Pd = Total Power Dissipation

Ta = Ambient Temperature

REGULATOR PROTECTION:

The MSK5102 series is fully protected against reversed input

polarity, overcurrent faults, overtemperature conditions (Pd) and

transient voltage spikes of up to 60V. If the regulator is used in dual

supply systems where the load is returned to a negative supply,

the output voltage must be diode clamped to ground.

OUTPUT CAPACITOR:

The output voltage ripple of the MSK5102 series voltage regulators

can be minimized by placing a filter capacitor from the output to

ground. The optimum value for this capacitor may vary from one

application to the next, but a minimum of 10µF is recommended

for optimum performance. Transient load response can also be

improved by placing a capacitor directly across the load.

LOAD CONNECTIONS:

In voltage regulator applications where very large load currents

are present, the load connection is very important. The path con-

necting the output of the regulator to the load must be extremely

low impedance to avoid affecting the load regulation specifications.

Any impedance in this path will form a voltage divider with the load.

ENABLE PIN:

The MSK5102 series of voltage regulators are equipped with a TTL

compatible ENABLE pin. A TTL high level on this pin activates the

internal bias circuit and powers up the device.ATTL low level on this

pin places the controller in shutdown mode and the device draws

approximately 10µA of quiescent current. If the enable function is

not used, simply connect the enable pin to the input.

First, the power dissipation must be calculated as follows:

Power Dissipation = (VIN - VOUT) x Iout

Next, the user must select a maximum junction temperature. The

maximum allowable junction temperature is 125°C. The equation

may now be rearranged to solve for the required heat sink to ambient

EXAMPLE:

An MSK5102-3.3 is configured for VIN=+5V and VOUT=+3.3V. Iout

is a continuous 1A DC level. The ambient temperature is +25°C.

The maximum desired junction temperature is 125°C.

Power Dissipation = (5V - 3.3V) x (1A)

In this example, a heat sink with a thermal resistance of no more

than 52°C/W must be used to maintain a junction temperature of

no more than 125°C.

1.7W

= 1.7 Watts

DEVICE SOLDERING/CASE CONNECTION:

The MSK5102 series are highly thermally conductive devices and

the thermal path from the package base to the internal junctions

is very short. Standard surface mount techniques should be used

when soldering the device into a circuit board. The external heat

sink/pad needs to be connected to ground because the base of

the MSK5102 is also electrically connected to ground. The user is

urged to keep this in mind when designing the printed circuit board

for the MSK5102. There should be no printed circuit traces making

contact with the base of the device except for ground. The ground

plane can be used to pull heat away from the device.

3

= 52.3°C/W

8548-36 Rev. D 5/15