SSZT206 December 2020 CSD17576Q5B , CSD19532Q5B

Power metal-oxide semiconductor field-effect transistor (MOSFET) data sheets provide useful information such as key specifications, ratings and characteristics to help you confirm that the device will operate as intended. You may have questions about how a parameter varies, however, so in this article I’ll explain not just what’s in the data sheet but more importantly, what’s not.

The second page of the data sheet includes the table of contents and the revision history. Next are the specifications tables, electrical characteristics and thermal information, followed by
graphs displaying the typical MOSFET
characteristics. Then there is a section on device and documentation support. The data sheet includes the mechanical, packaging and orderable information in
its final section. Unless otherwise noted, all specifications and ratings are at an ambient temperature, T_{A} = 25°C.

Figure 3 is the temperature variation of BV_{DSS} for two power
MOSFETs: the CSD17576Q5B 30-V trench FET and the CSD19532Q5B 100-V superjunction device; the curves in Figure 3 show the temperature dependence for BV_{DSS} as well as
I_{DSS} and I_{GS}. As the temperature increases, the breakdown
voltage for both increases nearly linearly. The slope of the line is the positive
temperature coefficient of BV_{DSS} and will differ based on the FET’s
process technology and voltage rating. Notice that the positive temperature
coefficient is less for the CSD19532Q5B than for the CSD17576Q5B.

Figure 4 shows the temperature dependence of I_{DSS} for the
CSD17576Q5B and CSD19532Q5B. The lower-voltage FET, the CSD17576Q5B, displays more
variation over the temperature range from -55°C to 150°C. For both devices, the
plots tend to flatten out at low temperatures. This is not actual behavior but a
test measurement system limitation at the very small currents being measures. The
device physics dictate a continual downward trend at low temperatures.

As shown in Figure 5 for the CD17576Q5B and CSD19532Q5B, I_{GSS} also has a
positive temperature variation. The relative increase in I_{GSS} is greater
for the CSD19532Q5B over the temperature range from -55°C to 150°C. Again, the
flattening of the curves at low temperatures is caused by the resolution of the test
measurement system.

The last parameter, g_{fs}, is
also temperature-dependent. You can use the transfer curves from the CSD17576Q5B and
CSD19532Q5B data sheets as shown in Figure 6 to estimate g_{fs} using Equation 1:

g_{fs} =
ΔI_{DS}/ΔV_{GS} (1)

Picking data points from the
data-sheet curves, Table 1 lists the estimated values for g_{fs}. You can
see that transconductance has a negative temperature coefficient.

**Table 1: Estimated g _{fs} values for the CSD17576Q5B**

You can make the same g_{fs}
estimates using the transfer characteristics for the CSD19532Q5B, as listed in Table
2.

**Table 2: Estimated gfs values for the CSD19532Q5B**

The easiest approach is to use a linear derating factor. From the graph, determine the SOA current, I_{DS(SOA)}, at the voltage, V_{DS(SOA)} and the pulse width of interest. Equation 2 calculates the SOA current at
temperature T (°C) as:

I_{DS(SOA@T)} = I_{DS(SOA)} × (T_{Jmax} - T)/(T_{Jmax} - 25°C) (2)

Equation 2 yields 0 current when T = T_{Jmax}, specified in the data sheet.

- Check out these technical articles:
- “Understanding MOSFET data sheets, Part 1 – UIS/avalanche ratings.”
- “Understanding MOSFET data sheets, Part 5 – Switching
Parameters.”
- Visit the TI MOSFET support and training center.
- Read the white paper, “Novel Thermally Enhanced Power Package.”
- Review the application report, “3D packaging advancements drive performance, power and density in power devices.”

- Jahdi, Saeed, Olayiwola Alatise, Roozbeh Bonyadi, Petros Alexakis, Craig Fisher, Jose A. Ortiz Gonzalez, Li Ran, and Philip Mawby “An Analysis
of the Switching Performance and Robustness of Power MOSFETs Body Diodes: A Technology Evaluation.”
*IEEE Transactions on Power Electronics*30, no. 5 (May 2015): pp. 2383-2394.