Datasheet AD7740 (Analog Devices)

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3 V/5 V Low Power, Synchronous Voltage-to-Frequency Converter AD7740* FEATURES FUNCTIONAL BLOCK DIAGRAM Synchronous Operation Full-Scale Frequency Set by External System Clock REFIN/OUT VDD 8-Lead SOT-23 and 8-Lead MSOP Packages 3 V or 5 V Operation AD7740 2.5V Low Power: 3 mW (Typ) REFERENCE Nominal Input Range: 0 to VREF True –150 mV Capability Without Charge Pump VREF Range: 2.5 V to VDD VIN X1 VOLTAGE-TO- Internal 2.5 V Reference FREQUENCY FOUT MODULATOR 1 MHz Max Input Frequency Selectable High Impedance Buffered Input Minimal External Components Required CLOCK APPLICATIONS GENERATION Isolation of High Common-Mode Voltages Low-Cost Analog-to-Digital Conversion BUF GND CLKOUT CLKIN Battery Monitoring Automotive Sensing GENERAL DESCRIPTION PRODUCT HIGHLIGHTS
The AD7740 is a low-cost, ultrasmall synchronous Voltage-to- 1. The AD7740 is a single channel, single-ended VFC. It is Frequency Converter (VFC). It works from a single 3.0 V to available in 8-lead SOT-23 and 8-lead MSOP packages, and is 3.6 V or 4.75 V to 5.25 V supply consuming 0.9 mA. The AD7740 intended for low-cost applications. The AD7740 offers is available in an 8-lead SOT-23 and also in an 8-lead MSOP considerable space saving over alternative solutions. package. Small package, low cost and ease of use were major design goals for this product. The part contains an on-chip 2.5 V 2. The AD7740 operates from a single 3.0 V to 3.6 V or 4.75 V bandgap reference but the user may overdrive this using an to 5.25 V supply and consumes typically 0.9 mA when the external reference. This external reference range includes VDD. input is unbuffered. It also contains an automatic power-down function. The full-scale output frequency is synchronous with the clock signal on the CLKIN pin. This clock can be generated with the 3. The AD7740 does not require external resistors and capaci- addition of an external crystal (or resonator) or supplied from a tors to set the output frequency. The maximum output CMOS-compatible clock source. The part has a maximum frequency is set by a crystal or a clock. No trimming or cali- input frequency of 1 MHz. bration is required. For an analog input signal that goes from 0 V to V 4. The analog input can be taken to 150 mV below GND for REF, the out- put frequency goes from 10% to 90% of f true bipolar operation. CLKIN. In buffered mode, the part provides a very high input impedance and accepts a 5. The specified voltage reference range on REFIN is from range of 0.1 V to VDD – 0.2 V on the VIN pin. There is also 2.5 V to the supply voltage, VDD. an unbuffered mode of operation that allows VIN to go from –0.15 V to VDD + 0.15 V. The modes are interchangeable using the BUF pin. The AD7740 (Y Grade) is guaranteed over the automotive temperature range of –40°C to +105°C. The AD7740 (K Grade) is guaranteed from 0°C to 85°C. *Protected under U.S. Patent # 6,147,528.
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