1.3 Second Buck Output for MCU, Radio or Sensor

While the bq25120 integrates a single, ultra-low power step-down converter for one rail, some systems, such as an MCU, radio or sensor, need a second high-efficiency rail with a different voltage. For these sub-systems, a discrete ultra-low power step-down converter with similar performance to the bq25120 converter is required. PMP11311 includes a TPS62743 which contains a user-selectable choice of 8 different output voltages from 1.2 V to 3.3 V.

If the more common 1.2-V or 1.8-V rail is needed, then the pin-to-pin compatible TPS62746 may be used instead to obtain the extra feature of an input voltage switch (VIN switch). The VIN switch allows a no-leakage measurement of the battery voltage by the host MCU. More details about the TPS62743 and TPS62746 and their implementation are found in the data sheets in the references. Either device requires a total solution size of less than 10 mm².

Figure 5. Schematic of Second Buck for MCU, Radio or Sensor Power