STMicroelectronics has introduced the STBP120 which protects the charging-control circuitry inside mobile phones and other battery-powered portable equipment in case the external charger applies an excessive voltage.

A number of variants are available, suitable for a range of charging-voltage levels including the USB voltages recommended by the current best-known proposals. These include YD/T 1591-2006 put forward by China’s Minister for Information and Industry (MII).

When implemented inside a battery-powered product, the STBP120 monitors the voltage from the connected charger. If the detected voltage exceeds a preset threshold, an internal solid-state switch is opened, thereby preventing the over-voltage from damaging the internal circuitry.

There are four variants spanning threshold values from 5.375V to 6.02V, allowing engineers to optimize for USB chargers at up to 5.25V or other chargers at higher voltages up to 6.8V.

Each device will protect against over-voltages as high as 28V. In normal operation the internal switch, an N-channel mosfet, has very low resistance of 90mohm to promote efficiency and minimise heat dissipation.

The STBP120 is delivered in a 2x2.5mm, 10-lead TDFN package.