Texas Instruments (TI) has introduced two tiny push-button reset controllers for 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.
Key features and benefits include: a selectable input delay of 7.5 or 12.5 seconds which eliminates unintended resets; low 250-nA quiescent current that conserves power for portable electronics; a selectable reset pulse of 400 or 800 milliseconds that allows for flexible initialising and a small 1.45-mm by 1.0-mm by 0.55-mm SON package that consumes 70 percent less board space than alternative 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 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.