SLVAF40 July   2021 TPS2661

 

  1.   Trademarks
  2. 1Introduction
  3. 2Discrete Solution With PTC
  4. 3TPS26610 Advantages to a Typical Solution
    1. 3.1 BOM and Size Reduction
    2. 3.2 Burden Resistor and Power Dissipation
    3. 3.3 Voltage Drop
    4. 3.4 Signal Good
    5. 3.5 Additional TPS26610 Features
      1. 3.5.1 Miswiring
      2. 3.5.2 Surge
      3. 3.5.3 Current-Loop Test During Installation (Unpowered)
      4. 3.5.4 High Accuracy For Current Measurements
  5. 4Conclusion

3.2 Burden Resistor and Power Dissipation

The 30-mA current limit granted by the TPS26610 allows the choice of a burden resistor with less constraints on maximum power dissipation. In overcurrent conditions the TPS26610 limits the current faster than the PTC in the typical solution.

Figure 3-2 shows that in the traditional solution the burden resistor has to dissipate more than 1.7 W in about four seconds until the PTC stabilizes to around 120 mW. Figure 3-3 shows the auto-retry feature of the TPS26610 decreasing the power dissipation on the burden resistor (less than 10 mW).


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Figure 3-2 PTC Overcurrent Response With VIN = 24 V (1 s/div) — 250-Ω Burden Resistor

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Figure 3-3 TPS26610 Overcurrent Response With VIN = 24 V (1 s/div) — 250-Ω Burden Resistor

Figure 3-5 and Figure 3-4 show the temperature of the two components during the same overcurrent condition. The temperature of the TPS26610 - Figure 3-5 is 37°C while the temperature of the PTC - Figure 3-4 is more than three times higher, specifically 120°C.


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Figure 3-4 PTC Thermal Image

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Figure 3-5 TPS26610 Thermal Image