Analog Angle Article

Clock/timer-IC family emulates versatility concept of venerable 555

Milpitas, CA—Many of you are familiar with the venerable 555 timer IC which included a multivibrator and comparator (see here), and gained wide popularity, and some cult status, as a creative building block in thousands of diverse, clever circuits; first marketed in 1971, it is still in fairly wide use.

Engendered with the same philosophical mindset, the TimerBlox family of tiny ICs from Linear Technology Corp. (LTC) provides clock- and timing-related building-block functions which users can adapt to a variety of needs, while off-loading their microcontroller and its active-mode power consumption. Members of the LTC6990 family function as voltage-controlled oscillator (VCO), low-frequency oscillator, pulse-width-modulated (PWM) oscillator, one-shot monostable pulse generator, and delay circuit, based on an all-silicon oscillator (with extreme vibration resistance and low tempco) with timing set entirely by user-supplied resistor(s).

The output of the ICs can source or sink up to 16 mA, compatible with direct drive of optoisolators and transformers, a common situation where PWM is used as a modulation scheme in a low-cost, basic galvanically isolated link. Greg Zimmer, Senior Product Marketing Engineer at LTC, pointed out that using the TimerBlox to supplement a microcontroller can provide both much higher timing/clocking accuracy and precision, while off-loading the processor from power-consuming housekeeping tasks that take it out of idle or quiescent mode and thus greatly increase power consumption. Applications include temperature/frequency conversion, motor control, LED dimming, isolation, debounce, long-interval timing (up to 9.5-hour period)

The first released member of the family, the LTC6990, is a VCO for 488 Hz to 2 MHz operation (bandwidth between 300 kHz and 1 MHz); subsequent members will be formally released in the next few weeks. It uses two resistors, to set center frequency and narrow/wide tuning range. The 2.25 to 5.5V, single-supply device requires 72 µamps at 100 kHz, and has 500 µsecond start-up. Support and tools: Given the building-block nature of these ICs, LT has compiled a downloadable collection of application circuits at , and also has LTSpice models with Spice III simulator, schematic capture, and a waveform viewer. There is also an Excel-based tool which assists designers in configuration, selection of resistor values, schematic generation, and generator of timing diagrams.—Bill Schweber

Price, packaging, and availability : The LTC6990 is available now, while other family members with different functions will be released in a few weeks. All ICs will be available in low-profile (1 mm) SOT-23 and 2mm x 3mm DFN. Versions are available in a variety of temperature-range grades, including –40o C to +125o C. Prices begin

For more information : contact Linear Technology Corp,

0 comments on “Clock/timer-IC family emulates versatility concept of venerable 555

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.