SLUAAX9 June   2025 BQ25756

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2MOSFET Power Losses in Buck and Boost Chargers
    1. 2.1 Buck Mode Losses
    2. 2.2 Boost Mode Losses
    3. 2.3 Closing Thoughts for FET Losses
  6. 3Evaluating MOSFETs Using the Design Calculator
    1. 3.1 Correlating MOSFET Data Sheet Parameters With the Design Calculator Parameters
    2. 3.2 Design Calculator MOSFET Comparison Example
  7. 4BOM Evaluation
  8. 5Summary
  9. 6References

1 Introduction

As the electrification of the grid, the automotive industry, and the internet of things (IoT) continues to proliferate, efficient power conversion becomes increasingly crucial for many systems today.

The BQ2575x family of devices is a series of charge controllers for Li-ion and LiFePO4 batteries. This family is comprised of the following devices as of the publication of this application note: the BQ25750, the BQ25756, the BQ25756E, the BQ25758, the BQ25758A, and the BQ25758S. These devices can be used to design an efficient buck or buck-boost topology for battery charging or DC-DC conversion. An example of a charger system that uses a BQ25756 charge controller is shown in Figure 1-1.

Example Application System Using a BQ25756 DeviceFigure 1-1 Example Application System Using a BQ25756 Device

This application note is a guide for the selection of the external MOSFETs used in combination with these devices. This is accomplished by

  • Explaining where losses in these charger systems come from.
  • Analyzing the key parameters typically included in MOSFET data sheets.
  • Explaining the usage of the design calculator for the BQ2575x devices.
  • Examining various BOMs that have been tested with the BQ2575x family of devices.