Micropac Industries cannot assume any responsibility for any circuits shown or represent that they are free from patent infringement.

Micropac reserves the right to make changes at any time in order to improve design and to supply the best product possible.

MICROPAC INDUSTRIES, INC. HYBRID MICROELECTRONICS PRODUCTS DIVISION

• 905 E. Walnut St., Garland, TX 75040 • (972) 272-3571 • Fax (972) 494-2281

www.micropac.com

05/16/01

PRELIMINARY DATA SHEET

53248

28 VDC SOLID STATE HIGH SIDE SELF-PROTECTED POWER CONTROLLER

APPLICATION INFORMATION

The cable harness occupies an important position in the total network to be protected. The wide variety and in

some cases considerable length and packing density used makes them particularly susceptible to persistent

overloads and overheating. The maximum current carrying capacity of a cable depends on its resistance, type of

insulation material and the ambient temperature. A cable, including insulation, generally consists of at least two

materials with different thermal capacitance and thermal resistance. The maximum temperatures of most cables

are at least +150°C (depending on the insulation properties) which is very close to the maximum junction

temperature of the SSPC (Shutdown). Since under overcurrent or short circuit conditions, the unit resistance per

these conditions, it is apparent that the SSPC can adequately protect properly selected cabling.

The following formulas provide methods for calculating the primary parameters.

Trip Current

1/2

= Maximum Trip Temperature

= Thermal Resistance, Junction to Ambient

= Ambient Temperature

On-state Resistance

With the above information, the temperature and current trip can be determined based upon the type of mounting

chosen and the ambient temperatures of operation.

Precaution

When a short circuit causes turn-off of the SSPC, precautions must be taken to limit transient voltages generated by

any inductance in the load. External protection is recommended, either across the switch or across the load, should

the application result in energies beyond this level.