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VCO offers 488Hz to 2MHz frequency range

Posted: 16 Aug 2010     Print Version  Bookmark and Share

Keywords:timer IC  clock IC  VCO 

Linear Technology Corp. (LTC) introduces the LTC6990, a member of the TimerBlox family that is a precision silicon oscillator with a programmable frequency range of 488Hz to 2MHz. 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 16mA, 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 9.5hour period)

The first released member of the family, the LTC6990, is a VCO for 488Hz to 2MHz operation (bandwidth between 300kHz and 1MHz); subsequent members will be formally released in the next few weeks. It uses two resistors, to set centre frequency and narrow/wide tuning range. The 2.25 to 5.5V, single-supply device requires 72µA at 100kHz, and has 500µs start-up.

Given the building-block nature of these ICs, LTC has compiled a downloadable collection of application circuits, 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.

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 (1mm) SOT-23 and 2mm x 3mm DFN. Versions are available in a variety of temperature-range grades, including -40�C to +125�C.

- Bill Schweber
  Planet Analog





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