OM183-15SC Ver la hoja de datos (PDF) - Omnirel Corp => IRF

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OM183-15SC

7.5A, 5A, 3A, 1.5A LOW DROPOUT FIXED VOLTAGE POSITIVE REGULATORS

Omnirel Corp => IRF 

OM183-5SC - OM186-15ST

APPLICATION NOTES

This family of three terminal regulators is easy to use and

has all the protection features that are expected in high

performance voltage regulators. They are short circuit

protected, have safe area protection as well as thermal

shutdown to turn off the regulator should the temperature

exceed about 165°C.

These regulators offer lower dropout voltage and more

precise reference tolerance. Further, the reference stability

with temperature is improved over older types of regulators.

The only circuit difference between using this family and

older regulators is that they require an output capacitor

for stability.

Overload Recovery

When power is first turned on, as the input voltage rises,

the output follows the input, allowing the regulator to start

up into very heavy loads. During the start-up, as the input

voltage is rising, the input-to-output voltage differential

remains small, allowing the regulator to supply large output

currents. With high input voltage, a problem can occur

wherein removal of an output short will not allow the output

voltage to recover. Older regulators, such as the 7800

series, also exhibited this phenomenon, so it is not unique

to the OM183-5.

The problem occurs with a heavy output load when the

input voltage is high and the output voltage is low, such as

immediately after a removal of a short. The load line for

such a load may intersect the output current curve at two

points. If this happens, there are two stable output

operating points for the regulator. With this double

intersection, the power supply may need to be cycled down

to zero and brought up again to make the output recover.

Thermal Conditions

This series of regulators has internal power and thermal

limiting circuitry designed to protect the device under

overload conditions. For continuous normal load conditions

however, maximum junction temperature ratings must not

be exceeded. It is important to give careful consideration to

all sources of thermal resistance from junction to ambient.

This includes junction to case, case to heat sink interface,

and heat sink resistance itself. New thermal resistance

specifications have been developed to more accurately

reflect device temperature and ensure safe operating

temperatures. The data section for these new regulators

provides a separate thermal resistance and maximum

junction temperature for both the Control Section and the

Power Transistor. Previous regulators, with a single

junction to case thermal resistance specification, used an

average of the two values provided here and therefore

could allow excessive junction temperature under certain

conditions of ambient temperature and heat sink resistance.

To avoid this possibility, calculations should be made for

both sections to ensure that both thermal limits are met.

Junction-to-case thermal resistance is specified from the

IC junction to the bottom of the case directly below the die.

This is the lowest resistance path for heat flow. Proper

mounting is required to ensure the best possible thermal

flow from this area of the package to the heat sink.

Thermal compound at the case-to-heat-sink interface is

strongly recommended. If the case of the device must be

electrically isolated, a thermally conductive spacer can be

used, as long as its added contribution to thermal

resistance is considered. Note that the case of all devices

in this series is electrically connected to the output.

MECHANICAL SPECIFICATIONS

P/N OM183SC and OM184SC JEDEC TO-258AA

MECHANICAL OUTLINE

PIN CONNECTION

.695

.165

.685

.155

.270

.240

.045

.035

.707

.697

.750

.500

.200 TYP.

.835

.815

.550

.530

.065

.055

.140 TYP.

.092 MAX.

.005

12 3

Pin 1 - Ground

Pin 2 - VOUT

Pin 3 - VIN

P/N OM185ST and OM186ST JEDEC TO-257AA

MECHANICAL OUTLINE

.200

.420

.190

.410

.045

.035

PIN CONNECTION

.665

.150

.645

.140

.537

.527

.430

.410

.038 MAX.

.750

.500

.005

1 23

Pin 1 - Ground

Pin 2 - VOUT

Pin 3 - VIN

.035

.100 TYP.

.025

.120 TYP.

3.3 - 69

3.3

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