/> The new STM6600 and STM6601 smart pushbutton on/off controller chips offer protection for battery-operated devices in many ways. These include minimizing the risk of powering up without sufficient battery energy to complete the sequence, which can damage the system. To prevent this, the chip blocks power-up if the battery is excessively discharged. It can also prevent ‘power-up’ if it detects a fault in the power supply. The IC connects directly to the power button and another Smart ResetTM input can be connect to any other pushbutton in the system, and contains circuitry to prevent external interference such as electrostatic discharges (ESD) from causing unwanted ‘power-up’ or ‘system-reset’.

As the latest members of ST’s family of power-path management chips, the STM660x ICs also implement Smart-Reset capabilities to help users recover products that have crashed or frozen during normal operation. Smart Reset requires both pushbuttons to be held down for a minimum period, controlled by an external capacitor, before a reset occurs. This two-action reset eliminates the need to hide the reset button behind a hole in the outer casing to prevent accidental use, thereby lowering engineering costs and allowing the casing to be sealed if required.

The protection features integrated in the STM660x devices replaces as many as 30 or 40 discrete components or a CPLD (Complex Programmable Logic Device) with a separate voltage regulator, clock and a voltage detector to determine the battery condition. Alternatively a microcontroller with dedicated housekeeping features could be used, but this, too, requires an external crystal, a voltage detector and must also be programmed.

The STM660x’s 2x3mm footprint occupies less than half the pc-board space of any alternative approach, which unlocks valuable space savings for mobile products. Also important to portable product designers is the device’s low active power consumption of 6µA and a zero-power shut-down mode consuming less than 1µA.