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REV. 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 which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. a AD654 Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: © Analog Devices, Inc., Low Cost Monolithic Voltage-to-Frequency Converter
FEATURES
Single or Dual Supply, 5 V to 36 V, 65 V to 618 V Full-Scale Frequency Up to 500 kHz Minimum Number of External Components Needed Versatile Input Amplifier Positive or Negative Voltage Modes Negative Current Mode High Input Impedance, Low Drift Low Power: 2.0 mA Quiescent Current Low Offset: 1 mV PRODUCT DESCRIPTION The AD654 is a monolithic V/F converter consisting of an input amplifier, a precision oscillator system, and a high current output stage. A single RC network is all that is required to set up any full scale (FS) frequency up to 500 kHz and any FS input voltage up to – 30 V. Linearity error is only 0.03% for a 250 kHz FS, and operation is guaranteed over an 80 dB dynamic range. The overall temperature coefficient (excluding the effects of external 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- cent current. The low drift (4 mV/°C typ) input amplifier allows operation directly from small signals such as thermocouples or strain gauges while offering a high (250 M W ) input resistance. Unlike most V/F converters, the AD654 provides a square-wave output, and can drive up to 12 TTL loads, optocouplers, long cables, or similar loads. PRODUCT HIGHLIGHTS 1. Packaged in both an 8-lead mini-DIP and an 8-lead SOIC 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 +V S) 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. 2. A minimum number of low cost external components are necessary. A single RC network is all that is required to set up any full scale frequency up to 500 kHz and any full-scale input voltage up to – 30 V. 3. Plastic packaging allows low cost implementation of the standard VFC applications: A/D conversion, isolated signal transmission, F/V conversion, phase-locked loops, and tuning switched-capacitor filters. 4. Power supply requirements are minimal; only 2.0 mA of quiescent current is drawn from the single positive supply from 4.5 volts to 36 volts. In this mode, positive inputs can vary from 0 volts (ground) to (+V S –4) volts. Negative inputs can easily be connected for below ground operation. 5. The versatile open-collector output stage can sink more than 10 mA with a saturation voltage less than 0.4 volts. The Logic Common terminal can be connected to any level between ground (or –V S) and 4 volts below +V S. This allows easy direct interface to any logic family with either positive or negative logic levels. FUNCTIONAL BLOCK DIAGRAM 321 58 7 6 AD654 DRIVER OSC FOUT LOGIC COMMON R T +VIN +VS C T C T –VS 2013 781/461.3113 C
–2– REV. AD654–SPECIFICATIONS (TA = +258C and VS (total) = 5 V to 16.5 V, unless otherwise noted. All testing done @ VS = +5 V.) AD654JN/JR Model Min Typ Max Units CURRENT-TO-FREQUENCY CONVERTER Frequency Range 0 500 kHz Nonlinearity1 fMAX = 250 kHz 0.06 0.1 % fMAX = 500 kHz 0.20 0.4 % Full-Scale Calibration Error C = 390 pF, IIN = 1.000 mA –10 +10 % vs. Supply (fMAX £ 250 kHz) VS = +4.75 V to +5.25 V 0.20 0.40 %/V VS = +5.25 V to +16.5 V 0.05 0.10 %/V vs. Temp (0°C to +70°C) 50 ppm/ °C ANALOG INPUT AMPLIFIER (Voltage-to-Current Converter) Voltage Input Range Single Supply 0 (+V S – 4) V Dual Supply –VS (+VS – 4) V Input Bias Current (Either Input) 30 50 nA Input Offset Current 5 nA Input Resistance (Noninverting) 250 MW Input Offset Voltage 0.5 1.0 mV vs. Supply VS = +4.75 V to +5.25 V 0.1 0.25 mV/V VS = +5.25 V to +16.5 V 0.03 0.1 mV/V vs. Temp (0°C to +70°C) 4 mV/°C OUTPUT INTERFACE (Open Collector Output) (Symmetrical Square Wave) Output Sink Current in Logic “0”2 VOUT = 0.4 V max, +25°C 10 20 mA VOUT = 0.4 V max, 0 °C to +70°C5 1 0 m A Output Leakage Current in Logic “1” 10 100 nA 0°C to +70°C 50 500 nA Logic Common Level Range –V S (+VS – 4) V Rise/Fall Times (CT = 0.01 mF) IIN = 1 mA 0.2 ms IIN = 1 mA1 ms POWER SUPPLY Voltage, Rated Performance 4.5 16.5 V Voltage, Operating Range Single Supply 4.5 36 V Dual Supply – 5 – 18 V Quiescent Current VS (Total) = 5 V 1.5 2.5 mA VS (Total) = 30 V 2.0 3.0 mA TEMPERATURE RANGE Operating Range –40 +85 °C NOTES 1At fMAX = 250 kHz; R T = 1 kW , CT = 390 pF, I IN = 0 mA–1 mA. 1At fMAX = 500 kHz; R T = 1 kW , CT = 200 pF, I IN = 0 mA–1 mA. 2The sink current is the amount of current that can flow into Pin 1 of the AD654 while maintaining a maximum voltage of 0.4 V between Pin 1 and Logic Common. Specifications shown in boldface are tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels. All min and max specifications are guaranteed, although only those shown in boldface are tested on all production units. Specifications subject to change without notice. C
Rev. C | Page 3 ABSOLUTE MAXIMUM RATINGS Parameter Rating Total Supply Voltage +VS to −VS 36 V Maximum Input Voltage (Pins 3, 4) to −VS −300 mV to +VS Maximum Output Current Instantaneous 50 mA Sustained 25 mA Logic Common to −VS −500 mV to (+VS –4) Storage Temperature Range −65°C to +150°C Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ESD CAUTION
should be adjusted until the desired FS frequency is indicated. converter will exhibit a zero output for inputs above (+VS – 3.5 V). Also, control currents above 2 mA will increase nonlinearity. of 0.9 mV are sufficient to cause momentary malfunction. guard rings or shielding may be required. Figure 5. Input Protection
100 W ) in the supply lines to provide a measure of decoupling
the AD654. A proper ground scheme appears in Figure 6. Figure 6. Proper Ground Scheme temperatures is shown in Figure 7. Figure 7. Typical Nonlinearities at Different Full-Scale
Rev. C | Page 12 ORDERING GUIDE Model1 Temperature Range Package Description Package Option AD654JN –40°C to +85°C 8-Lead PDIP N-8 AD654JNZ –40°C to +85°C 8-Lead PDIP N-8 AD654JNZ/+ –40°C to +85°C 8-Lead PDIP N-8 AD654JR –40°C to +85°C 8-Lead SOIC_N R-8 AD654JR-REEL –40°C to +85°C 8-Lead SOIC_N R-8 AD654JR-REEL7 –40°C to +85°C 8-Lead SOIC_N R-8 AD654JRZ –40°C to +85°C 8-Lead SOIC_N R-8 AD654JRZ-REEL –40°C to +85°C 8-Lead SOIC_N R-8 AD654JRZ-REEL7 –40°C to +85°C 8-Lead SOIC_N R-8 1 Z = RoHS Compliant Part.
REVISION HISTORY
7/13—Rev. B to Rev. C 12/99—Rev. A to Rev. B ©2013 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the prop erty of their respective owners. D11523-0-7/13(C)