Two tiny push-button reset controllers from Texas Instruments suit space-constrained, power-sensitive applications such as pedometers, fitness bands, cell phones and tablets. The dual-channel TPS3420 and TPS3421 feature low power consumption and a selectable reset time delay to improve system stability.
Push-button reset controllers are required for portable electronics with an embedded battery. In practice, the user presses and holds one or two external keys for a specific period of time, which turns the portable device off or generates a reset. The TPS3420 and TPS3421 use a long input delay to provide the intended system reset and avoid reset from short push-button or key presses. This reset configuration enables differentiation between software interrupts and hard system resets. The timers are the first in a family of new push-button controllers from TI to ensure a hard and full system reset when needed to increase efficiency.
· Selectable input delay of 7.5 or 12.5 seconds eliminates unintended resets.
· Low 250-nA quiescent current conserves power for portable electronics.
· Selectable reset pulse of 400 or 800 milliseconds allows for flexible initializing.
· Small 1.45-mm by 1.0-mm by 0.55-mm SON package consumes 70 percent less board space than competitive devices.
Although TI's MSP430 microcontrollers (MCUs) are already equipped with a push-button interrupt, an external push-button reset controller, such as the TPS3420 or TPS3421, along with a voltage supervisor like the TPS3839, can serve as an extra line of security. The controller and supervisor remain isolated from the MSP430 MCU, ensuring reset as long as they are connected to a power supply. The TPS3420 and TPS3421 also relieve the MSP430 MCU of the processing power required to monitor a push-button interrupt.
The TPS3420 and TPS3421 push-button reset controllers are available in volume now from TI and its authorized distributors. Offered in a 6-pin SON package, the controllers are priced at US$0.40 in 1,000-unit quantities. For those applications requiring a single push-button input, TI offers the TPS3422 priced at US$0.34.