From smartphones to cars, consumers are demanding more functionality packed into smaller and smaller products. To help achieve this goal, TI has optimized packaging techniques for its semiconductor devices, including load switches for subsystem control and power sequencing. Packaging innovations enable higher power densities, allowing more semiconductor devices and functions to be packed per printed circuit board.
Wafer Level Chip Packaging (WCSP)
Currently, the smallest load switches are in wafer-level chip-scale packaging (WCSP). Figure 1 shows an example of a four-pin WCSP device.
Figure 1: Four-pin WCSP device
WCSP technology uses a silicon die and attaches solder balls to the bottom, allowing the package size to be as small as possible and making the technology very competitive in terms of current-carrying capacity and package area. Because the WCSP minimizes the form factor, the number of solder balls used for the input and output pins will limit the maximum current that the load switch can support.
Plastic package with wire bonding technology
Applications requiring higher currents or more demanding manufacturing processes such as industrial PCs require plastic packaging. Figure 2 shows a plastic package implementation using wire bonding technology.
Figure 2: Standard wire-bonded Quad-Flat No Lead (QFN) package
The QFN or Small-Outline No Lead (SON) package uses wire-bonding technology to connect the chip to the leads, allowing greater current to flow from the input to the output while providing good thermal characteristics for self-heating. But wire-bonded plastic packages require a lot of space for the bond wires themselves, requiring a larger package compared to the chip size itself. The bond wires can also increase the resistance of the power path, thereby increasing the overall on-resistance of the load switch. In this case, the compromise is a balance between larger size and higher power support.
Plastic HotRod Package
While both WCSP and wire-bond packaging have their advantages and limitations, TI’s HotRod QFN load switches combine the best of both packaging technologies. Figure 3 shows an exploded view of the HotRod package.
Figure 3: TI HotRod QFN structure and chip connections
These leadless plastic packages use copper pillars to connect the chip to the package, and because this method requires less space than bond wires, the package size can be minimized. The copper pillars also support high current levels and add minimal resistance to the current path, allowing a single pin to carry up to 6A.
Table 1 illustrates these advantages by comparing the TPS22964C WCSP, TPS22975 wire-bonded SON, and TPS22992 load switch.
Table 1: Comparison of various load switch solutions
While the TPS22975 wire-bonded SON device can also support 6A, achieving this current level requires the use of two pins to supply the input and output voltages, which limits the number of other features such as power good and adjustable rise time. Bond wires can also increase the on-resistance of the device, thereby limiting the maximum current.
The WCSP load switch is the smallest of the three solutions, but its limited pins allow it to have the least functionality and support the lowest current.
Epilogue
The TPS22992 load switch combines the advantages of WSCP and SON, combining the small size of a WCSP solution with the high current support and extra features of a wire-bonded SON solution. TI’s TPS22992 and TPS22998 load switches use the HotRod package to optimize small solution size while supporting high current, low on-resistance and many device features.
Other resources
● Read the technical white paper “When to Change Switches to Integrated Load Switches”.
● Read the application report “Basics of Load Switches” to learn more about load switches.
● Read the e-book “11 Ways to Protect Your Power Path” for design tips.
● Read the application report “Enhanced HotRod QFN Package: Achieving Low EMI Performance in the Industry’s Smallest 4A Converter”.
● Check out TI’s QFN and WCSP packaging solutions.
About Texas Instruments (TI)
Texas Instruments (TI) (NASDAQ: TXN) is a global semiconductor company that designs, manufactures, tests and sells analog and embedded processing chips for industrial, automotive, personal electronics, communications Markets such as devices and enterprise systems. We are committed to making electronics more affordable and creating a better world through semiconductor technology. Today, each generation of innovation builds on the innovation of the previous generation, making our technology smaller, faster, more reliable, and more affordable, enabling semiconductors to be widely used in electronics. This is the advancement of engineering. . This is exactly what we have been doing for decades and now. For more information, please visit the company’s website www.ti.com.cn.
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