Optimizing power density with eFuses


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Increased bandwidth demands have made power density more important for electronic equipment like servers, routers and switches as circuit board space becomes more constrained. As a result, power integrated circuits (ICs) must pass more power (with a lower on-resistance [RON]) in a smaller footprint. Often this relationship between RON and footprint size is inversely related – optimizing one will worsen the other.

One subset of power ICs that has seen significant innovation in recent years is the hot-swap controller. Historically, external metal-oxide semiconductor field-effect transistor (MOSFET) hot-swap controllers have been a very popular power-path protection solution. However, the footprint for such a solution can be quite large given the need for an external sense resistor and power MOSFET. As shown in Figure 1, a hot-swap solution can take up a significant amount of board space.

Figure 1: An external MOSFET solution with the TPS2477x hot-swap controller

Decreasing the package size of these ICs will increase the RON, which will worsen the power performance. However, with TI’s proprietary processes, it is possible to optimize both parameters and achieve superior power density in a very small footprint. Figure 2 shows the TPS25982 – a new 24-V, 15-A eFuse that comes in a 4-mm-by-4-mm package.

Figure 2: TPS25982 (center) and TPS2595 (right) size comparison

For even smaller footprint solutions, the TPS2595 eFuse comes in a 2mm x 2mm package and for higher voltages, the TPS1663 eFuse supports up to 60V, as shown below in Table 1.

Device

Voltage

Current

RON

Package

TPS25982

2.7 V-24 V

15 A

3 mΩ

4-mm-by-4-mm quad flat no-lead (QFN)

TPS2595

2.7 V-18 V

4 A

34 mΩ

2-mm-by-2mm QFN

TPS1663

4.5 V-60 V

6 A

31 mΩ

4-mm-by-4mm QFN

Table 1: Texas Instruments eFuse options

As overall power demands increase in the market, board space becomes more and more valuable. As a result, optimizing power efficient solutions in a small footprint will be something all power designers will have to consider.