SDAA050 August   2025 BQ25180 , BQ25186 , BQ25188 , BQ25622E , BQ25638 , BQ25798 , BQ25890 , TPS2121

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Possible Architectures
    1. 2.1 Power Mux
      1. 2.1.1 Other Power Mux Considerations
      2. 2.1.2 Power Mux Over Voltage and Priority Settings
      3. 2.1.3 Power Mux Testing
    2. 2.2 Multicell Charger IC
    3. 2.3 Dual Chargers
    4. 2.4 eFuses (USB OTG)
  6. 3Summary
  7. 4References

2.4 eFuses (USB OTG)

As most TI power muxes do not allow for reverse current, the USB OTG feature which allows the battery charger IC to boost the battery voltage and act as a power source is not available. This can however be accomplished using two eFuses. In most dual source applications both sources are not USB OTG ports, and as a result, for greatest cost effectiveness a unidirectional eFuse must be used for the non-USB OTG source, while a bidirectional eFuse is used for the USB OTG port.

The parts selected for this example are the TPS25948 bidirectional eFuse and the LM7310 unidirectional eFuse. The TPS25948 typical application diagram in the data sheet features the use of two of these eFuses along with a battery charging IC.

Application Diagram for Dual Source Using eFuses Figure 2-11 Application Diagram for Dual Source Using eFuses

One feature of note is the connection of the second eFuse output to the PMID pin of the battery charger IC. The PMID pin provides a direct connection to the node between the back to back FETs in the battery charger IC and is usually used for an additional decoupling capacitor. Note that for some chargers the OTG output must be taken from the PMID pin (for example, BQ2589x) while on other chargers the OTG output must be taken from VBUS (for example, BQ25638).

Section of the Application Diagram Figure 2-12 Section of the Application Diagram