New Industry Products

40mA Linear Charger for Thin-Film Batteries in Wearables and IoT

May 14, 2019 by Scott McMahan

The STBC15 from STMicroelectronics is a linear charger thin-film battery that has a maximum charging current of 40mA. A CC/CV algorithm is used to charge the battery.

With the help of an ultra-low consumption architecture, the charger is suited for low-capacity cells such as thin-film batteries, and it can use low energy sources including energy harvesters. A 5V input such as a standard USB port can be used as a voltage source as well. A specific version (-L) is available to charge Li-Ion cells.

Applications for the charger include portable IoT devices, energy harvesting, smart cards, wireless sensor nodes, portable health care devices, and wearable devices for fitness and wellness.

In order to prevent battery damage under fault conditions, the  STBC15 integrates over-current and over-discharge circuitry.

Dedicated selection inputs allow the setting of the floating voltage to four different values. The -L version features a higher set of floating voltages, suitable for Li-Ion batteries. A dedicated pin lets the device be set in shelf-mode. In this state, the STBC15 consumes less than 10nA, thereby not discharging the battery before the end user activates the final device.

The ultra-low power architecture allows the STBC15 to consume less than 250nA when the input power source is removed and less than 10nA in over-discharge-mode. The device is available in a (1.7mm × 2.0 mm) 12-lead QFN package, 400µm pitch, 0.55mm max. thickness or in a flip-chip package (1.1mm x 1.4mm with 12 bumps 300µm pitch).

Key Features

  • Charges thin film battery with CC-CV algorithm
  • L version suitable for Li-Ion batteries
  • Charging current up to 40mA (selectable by dedicated pins)
  • 250nA battery leakage current
  • Reverse current protection from battery to supply input
  • Programmable floating voltage with 0.5% accuracy
  • Battery over-current protection
  • Battery over-discharge protection switch totally disconnects battery for cell durability
  • Shelf-mode supported, no battery mechanical switch needed
  • Power-Good open-drain output
  • Valid source open drain output
  • Peak mode input to avoid over-discharge false triggering
  • Available packages:
    • QFN12 measuring 1.7mm x 2.0mm, thickness 0.55mm max.
    • Flip-chip 12 measuring 1.1mm x 1.4mm, 300µm pitch