MSK5230-25 Datasheet, PDF (3/6 Pages) M.S. Kennedy Corporation – Hermetic Surface Mount Package

APPLICATION NOTES
REGULATOR PROTECTION:
The MSK5230 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 MSK5230 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
20µF is recommended for optimum performance. Transient
load response can also be improved by placing a capacitor
directly across the load. The capacitor should not be an
ultra-low ESR type. Tantalum capacitors are best for fast
load transients but aluminum electrolytics will work fine in
most applications.
LOAD CONNECTIONS:
In voltage regulator applications where very large load
currents are present, the load connection is very important.
The path connecting 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.
MINIMIZING POWER DISSIPATION:
Many applications can not take full advantage of the ex-
tremely low dropout specifications of the regulator due to
large input to output voltage differences. The simple circuit
below illustrates a method to reduce the input voltage at the
regulator to just over the dropout specification to keep the
internal power dissipation minimized:
PACKAGE CONNECTIONS:
The MSK5230 series are highly thermally conductive de-
vices and the thermal path from the package heat sink to
the internal junctions is very short. Standard surface mount
soldering techniques should be used when mounting the
device. Some applications may require additional heat
sinking of the device.
HEAT SINK SELECTION:
To select a heat sink for the MSK5230, the following formula
for convective heat flow may be used.
Governing Equation:
Tj = Pd x (Rθjc + Rθcs + Rθsa) + Ta
WHERE:
Tj = Junction Temperature
Pd = Total Power Dissipation
Rθjc = Junction to Case Thermal Resistance
Rθcs = Case to Heat Sink Thermal Resistance
Rθsa = Heat Sink to Ambient Thermal Resistance
Ta = Ambient Temperature
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 absolute maximum allowable junction temperature is
125°C. The equation may now be rearranged to solve for
the required heat sink to ambient thermal resistance (Rθsa).
EXAMPLE:
An MSK5230-3.3 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.
Rθjc = 3.3°C/W and Rθcs = 0.5°C/W typically.
Power Dissipation = (5V - 3.3V) x (1A)

= 1.7 Watts
Solve for Rθsa:
[ ] Rθsa = 125°C - 25°C - 3.3°C/W - 0.5°C/W
1.7W
In this example, a heat sink with a thermal resistance of
no more than 55°C/W must be used to maintain a junction
temperature of no more than 125°C.
For a given continuous maximum load of 1 amp, R1 can be
selected to drop the voltage seen at the regulator to 4V. This
allows for the output tolerance and dropout specifications.
Input voltage variations (5V) also should be included in the
calculations. The resistor should be sized according to the
power levels required for the application.
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8548-39 Rev. J 4/15