9.1.4 Safe Operating Area (SOA)

The SOA curves in Figure 33 show the continuous current carrying capability of the device versus ambient temperature (T_A) to ensure reliable operation over 100,000 hours of device lifetime. Each curve represents a specific percent of time that the switch is on.

The 100% curve represents use for a full 24 hours in a day. The 75% curve indicates 18 hours of use in a day while the 12.5% curve shows 3 hours of use per day.

Examples on how to use this plot:

• The application has an ambient temperature of 60°C and the switch will be on 100% of the time. The maximum continuous current that can be applied is approximately 2.1 A.
• The application requires the switch to be on 12.5% of the time and the current while on will be 3 A. The maximum ambient temperature is approximately 100°C.
• The application requires 2 A and will be operated at 70°C. The switch can be on for a maximum of 75% of the time.
• It is expected that most applications will not have specific use cases as defined in the examples above. Different use cases can be combined to generate a more complete view of a specific application. This example shows use under various conditions simplified to an average use case. The application requires operation at 4 A for 25% of the time, 1 A for 25% of the time and is off the remaining 50% of the time. Ambient temperature will vary from 25°C to 50°C. Will there be any limitations? The average current can be calculated as (4 A × 25% + 1 A * 25% + 0 A * 50%). The average current calculates to be 1.25 A. Assuming worst case temperature of 50°C, the resulting application is within the safe operating area.

Figure 33. Safe Operating Area