LTC6990 - TimerBlox: Voltage Controlled Silicon Oscillator - Linear Technology - #1

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LTC6990 1 6990f TYPICAL APPLICATION DESCRIPTION TimerBlox: Voltage Controlled Silicon Oscillator The LTC®6990 is a precision silicon oscillator with a programmable frequency range of 488Hz to 2MHz. It can be used as a fi xed-frequency or voltage-controlled oscillator (VCO). The LTC6990 is part of the TimerBlox™ family of versatile silicon timing devices. A single resistor, RSET, programs the LTC6990’s internal master oscillator frequency. The output frequency is determined by this master oscillator and an internal frequency divider, NDIV, programmable to eight settings from 1 to 128. fOUT = 1MHz NDIV • 50kÙ RSET ,NDIV = 1, 2, 4 …128 Optionally, a second resistor at the SET input provides linear voltage control of the output frequency and can be used for frequency modulation. A narrow or wide VCO tuning range can be confi gured by the appropriate selection of the two resistors. The LTC6990 includes an enable function that is synchronized with the master oscillator to ensure clean, glitch-free output pulses. The disabled output can be confi gured to be high impedance or forced low. The LTC6990 is available in the 6-lead SOT-23 (ThinSOT) package or a 6-lead 2mm × 3mm DFN. Voltage Controlled Oscillator with 16:1 Frequency Range L, LT, LTC and LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. TimerBlox and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 6342817, 6614313. FEATURES APPLICATIONS n Fixed-Frequency or Voltage-Controlled Operation – Fixed: Single Resistor Programs Frequency with <2.2% Max Error – VCO: Two Resistors Set VCO Center Frequency and Tuning Range n Frequency Range: 488Hz to 2MHz n 2.25V to 5.5V Single Supply Operation n 72ìA Supply Current at 100kHz n 500ìs Start-Up Time n VCO Bandwidth >300kHz at 1MHz n CMOS Logic Output Sources/Sinks 20mA n 50% Duty Cycle Square Wave Output n Output Enable (Selectable Low or Hi-Z When Disabled) n –40°C to 125°C Operating Temperature Range n Available in Low Profi le (1mm) SOT-23 (ThinSOT™) and 2mm × 3mm DFN Package n Low Cost Precision Programmable Oscillator n Voltage-Controlled Oscillator n High Vibration, High Acceleration Environments n Replacement for Fixed Crystal and Ceramic Oscillators n Portable and Battery-Powered Equipment VCO Transfer Function VCTRL (V) 0 fOUT (kHz) 1000 750 250 500 0 0.5 6990 TA01b 1 1.5 2 6990 TA01a LTC6990 OE GND SET OUT V+ DIV C1 0.1ìF RSET 100k V+ V+ VCTRL RVCO 100k fOUT .. 1MHz .. VCTRL • 0.5 MHz V