Low frequency clock IC supports long duration power-on reset/watchdog timers

March 27, 2013 // By Graham Prophet
Linear Technology's LTC6995 is a simple, accurate low frequency clock configurable for long duration power-on reset and watchdog timer applications. The LTC6995 is the latest part in the TimerBlox family of versatile silicon timing devices, which combines an accurate programmable oscillator with precision circuitry and logic.

An extremely wide resistor-settable frequency range provides a clock period from 1msec to 9.5 hours. Upon power-on or a reset signal, the LTC6995 will initiate a full output clock cycle. The reset capability and programmable period are specifically intended for long duration timing events.

The LTC6995 is simply programmed, using 1 to 3 resistors, with a maximum frequency error guaranteed less than 1.5%. The reset function will truncate the output pulse, clear the internal dividers and hold the output in a high or low state. The polarity of the reset input and the output signal can be configured for active-low or active-high operation. Two versions of the LTC6995 are available, with inverted reset functionality; the reset on the LTC6995-1 is active high, and active low for the LTC6995-2. The output polarity in the reset condition is selectable for both versions.

TimerBlox devices are solid state and can be operated under high acceleration, vibration and temperature extremes. They require no timing capacitors, crystals, microcontroller or programming. These devices offer higher accuracy and stability, and lower power consumption than typical resistor/capacitor-based oscillators. They generate a square wave output with 50% duty cycle, use 55µA to 80µA supply current from 2.25V to 5.5V, have a 500µsec start-up time and their 20mA source and sink capability enables direct driving of opto-isolators for electrical isolation. Fully specified over the temperature range of -55°C to 125°C, the TimerBlox devices are suitable for automotive and industrial applications, where many oscillators and microcontrollers are unable to operate. The small SOT23 footprint allows each timing device to be placed at the point of use, without routing signals over long distances, providing an ideal timer for space-limited applications such as handheld and portable devices.

LTC6995costs $1.35 (1,000): more information; www.linear.com/product/LTC6995