Datasheet AD654 (Analog Devices)

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Low Cost Monolithic Voltage-to-Frequency Converter AD654 FEATURES FUNCTIONAL BLOCK DIAGRAM Low Cost Single or Dual Supply, 5 V to 36 V,
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5 V to
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18 V +VS CT CT –VS Full-Scale Frequency Up to 500 kHz 8 7 6 5 Minimum Number of External Components Needed Versatile Input Amplifier Positive or Negative Voltage Modes DRIVER OSC Negative Current Mode High Input Impedance, Low Drift AD654 Low Power: 2.0 mA Quiescent Current Low Offset: 1 mV 1 2 3 4 F LOGIC +V OUT RT IN COMMON PRODUCT DESCRIPTION
2. A minimum number of low cost external components are The AD654 is a monolithic V/F converter consisting of an input necessary. A single RC network is all that is required to set amplifier, a precision oscillator system, and a high current output up any full scale frequency up to 500 kHz and any full-scale stage. A single RC network is all that is required to set up any input voltage up to ± 30 V. full scale (FS) frequency up to 500 kHz and any FS input voltage 3. Plastic packaging allows low cost implementation of the up to ± 30 V. Linearity error is only 0.03% for a 250 kHz FS, standard VFC applications: A/D conversion, isolated signal and operation is guaranteed over an 80 dB dynamic range. The transmission, F/V conversion, phase-locked loops, and tuning overall temperature coefficient (excluding the effects of external switched-capacitor filters. components) is typically ± 50 ppm/°C. The AD654 operates from a single supply of 5 V to 36 V and consumes only 2.0 mA quies- 4. Power supply requirements are minimal; only 2.0 mA of cent current. quiescent current is drawn from the single positive supply from 4.5 volts to 36 volts. In this mode, positive inputs can The low drift (4 µV/°C typ) input amplifier allows operation vary from 0 volts (ground) to (+V directly from small signals such as thermocouples or strain gauges S –4) volts. Negative inputs can easily be connected for below ground operation. while offering a high (250 MΩ) input resistance. Unlike most V/F converters, the AD654 provides a square-wave output, and 5. The versatile open-collector output stage can sink more than can drive up to 12 TTL loads, optocouplers, long cables, or 10 mA with a saturation voltage less than 0.4 volts. The Logic similar loads. Common terminal can be connected to any level between ground (or –VS) and 4 volts below +VS. This allows easy
PRODUCT HIGHLIGHTS
direct interface to any logic family with either positive or 1. Packaged in both an 8-lead mini-DIP and an 8-lead SOIC negative logic levels. package, the AD654 is a complete V/F converter requiring only an RC timing network to set the desired full-scale fre- quency and a selectable pull-up resistor for the open-collector output stage. Any full scale input voltage range from 100 mV to 10 volts (or greater, depending on +VS) can be accommo- dated by proper selection of the timing resistor. The full- scale frequency is then set by the timing capacitor from the simple relationship, f = V/10 RC. REV. C Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties
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