SLPS598C May   2017  – January 2018

PRODUCTION DATA.

1. 1Features
2. 2Applications
3. 3Description
4. 4Revision History
5. 5Specifications
6. 6Application and Implementation
7. 7Layout
1. 7.1 Layout Guidelines
2. 7.2 Layout Example
8. 8Device and Documentation Support
9. 9Mechanical, Packaging, and Orderable Information

#### Package Options

Refer to the PDF data sheet for device specific package drawings

• DMM|22

### 6.6 Design Example – Regulate Current to Maintain Safe Operation

If the case and board temperature of the power block are known, the SOA can be used to determine the maximum allowed current that will maintain operation within the safe operating area of the device. The following procedure outlines how to determine the RMS current limit while maintaining operation within the confines of the SOA, assuming the temperatures of the top of the package and PCB directly underneath the part are known.

1. Start at the maximum current of the device on the Y-axis and draw a line from this point at the known top case temperature to the known PCB temperature.
2. Observe where this point intersects the TX line.
3. At this intersection with the TX line, draw vertical line until you hit the SOA current limit. This intercept is the maximum allowed current at the corresponding power block PCB and case temperatures.

In the example below, we show how to achieve this for the temperatures TC = 124°C and TB = 120°C. First we draw from 50 A on the Y-axis at 124°C to 120°C on the X-axis. Then, we draw a line up from where this line crosses the TX line to see that this line intercepts the SOA at 39 A. Thus we can assume if we are measuring a PCB temperature of 124°C, and a top case temperature of 120°C, the power block can handle 39-A RMS, at the normalized conditions. At conditions that differ from those in Figure 1, the user may be required to make an SOA temperature adjustment on the TX line, as shown in the next section.

Figure 20. Regulating Current to Maintain Safe Operation