Monolithic Synchronous Voltage-to-Frequency Converter AD652 The AD652 is available in five performance grades. The 20-lead FEATURES PLCC-packaged JP and KP grades are specified for operation Full-scale frequency (up to 2 MHz) set by external system clock over the 0C to +70C commercial temperature range. The Extremely low linearity error (0.005% max at 1 MHz FS, 16-lead CERDIP-packaged AQ and BQ grades are specified for 0.02% max at 2 MHz FS) operation over the 40C to +85C industrial temperature No critical external components required range. The AD652SQ is available for operation over the full Accurate 5 V reference voltage 55C to +125C extended temperature range. Low drift (25 ppm/C max) PRODUCT HIGHLIGHTS Dual- or single-supply operation Voltage or current input 1. The use of an external clock to set the full-scale frequency MIL-STD-883 compliant versions available allows the AD652 to achieve linearity and stability far superior to other monolithic VFCs. By using the same clock PRODUCT DESCRIPTION to drive the AD652 and set the counting period (through a The AD652 synchronous voltage-to-frequency converter suitable divider), conversion accuracy is maintained (SVFC) is a powerful building block for precision analog-to- independent of variations in clock frequency. digital conversion, offering typical nonlinearity of 0.002% 2. The AD652 synchronous VFC requires only one external (0.005% maximum) at a 100 kHz output frequency. The inher- component (a noncritical integrator capacitor) for ent monotonicity of the transfer function and wide range of operation. clock frequencies allow the conversion time and resolution to 3. The AD652 includes a buffered, accurate 5 V reference. be optimized for specific applications. 4. The AD652s clock input is TTL and CMOS compatible and The AD652 uses a variation of the charge-balancing technique can also be driven by sources referred to the negative power to perform the conversion function. The AD652 uses an supply. The flexible open-collector output stage provides external clock to define the full-scale output frequency, rather sufficient current sinking capability for TTL and CMOS than relying on the stability of an external capacitor. The result logic, as well as for optical couplers and pulse transformers. is a more stable, more linear transfer function, with significant A capacitor-programmable one-shot is provided for selec- application benefits in both single- and multichannel systems. tion of optimum output pulse width for power reduction. Gain drift is minimized using a precision low drift reference 5. The AD652 can also be configured for use as a synchronous and low TC, on-chip, thin-film scaling resistors. Furthermore, F/V converter for isolated analog signal transmission. initial gain error is reduced to less than 0.5% by the use of laser- 6. The AD652 is available in versions compliant with wafer-trimming. MILSTD-883. Refer to the Analog Devices Military The analog and digital sections of the AD652 have been Products Databook or current AD652/883B data sheet for designed to allow operation from a single-ended power source, detailed specifications. simplifying its use with isolated power supplies. FUNCTIONAL BLOCK DIAGRAM CLOCK IN R IN COMPARATOR C INT D FLOP LATCH V IN ONE CK G Q SHOT AND D Q D Q INTEGRATOR C OS 5V HL 1mA V S Figure 1. 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 that may result from its use. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Specifications subject to change without notice. No license is granted by implication Tel: 781.329.4700 www.analog.com or otherwise under any patent or patent rights of Analog Devices. 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All rights reserved. 00798-001AD652 TABLE OF CONTENTS Specifications..................................................................................... 3 Component Selection ................................................................ 12 Absolute Maximum Ratings............................................................ 5 Digital Ground............................................................................ 13 ESD Caution.................................................................................. 5 Single-Supply Operation ........................................................... 14 Definitions of Specifications....................................................... 5 Frequency-to-Voltage Converter ............................................. 15 Theory of Operation ........................................................................ 6 Decoupling and Grounding...................................................... 16 Overrange...................................................................................... 8 Frequency Output Multiplier.................................................... 17 SVFC Connection for Dual Supply, Positive Input Voltages .. 9 Single-Line Multiplexed Data Transmission .......................... 18 SVFC Connections for Negative Input Voltages ...................... 9 Isolated Front End...................................................................... 22 SVFC Connection for Bipolar Input Voltages ........................ 10 A-to-D Conversion .................................................................... 22 PLCC Connections..................................................................... 11 Delta Modulator ......................................................................... 23 Gain and Offset Calibration...................................................... 11 Bridge Transducer Interface...................................................... 24 Gain Performance ...................................................................... 12 Outline Dimensions ....................................................................... 25 Reference Noise .......................................................................... 12 Ordering Guide............................................................................... 26 Digital Interfacing Considerations........................................... 12 REVISION HISTORY 5/04Data Sheet Changed from Rev. B to Rev. C Updated Format..............................................................Universal Changes to Gain and Offset Calibration section.................... 11 Updated Outline Dimensions ................................................... 25 Changes to Ordering Guide ...................................................... 26 2/00Data Sheet Changed from Rev. A to Rev. B Rev. C Page 2 of 28