The AD7740 is a low-cost, ultrasmall synchronous Voltage-to-Frequency Converter (VFC). It works from a single 3.0 V to 3.6 V or 4.75 V to 5.25 V supply consuming 0.9 mA. The AD7740 is available in an 8-lead SOT-23 and also in an 8-lead MSOP 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 bandgap reference but the user may overdrive this using an external reference. This external reference range includes VDD.
The full-scale output frequency is synchronous with the clock signal on the CLKIN pin. This clock can be generated with the addition of an external crystal (or resonator) or supplied from a CMOS-compatible clock source. The part has a maximum input frequency of 1 MHz.
For an analog input signal that goes from 0 V to VREF, the output frequency goes from 10% to 90% of fCLKIN. In buffered mode, the part provides a very high input impedance and accepts a range of 0.1 V to VDD – 0.2 V on the VIN pin. There is also 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.
Product Highlights
1. The AD7740 is a single channel, single-ended VFC. It is available in 8-lead SOT-23 and 8-lead MSOP packages, and is intended for low-cost applications. The AD7740 offers considerable space saving over alternative solutions.
2. The AD7740 operates from a single 3.0 V to 3.6 V or 4.75 V to 5.25 V supply and consumes typically 0.9 mA when the input is unbuffered. It also contains an automatic power-down function.
3. The AD7740 does not require external resistors and capacitors to set the output frequency. The maximum output frequency is set by a crystal or a clock. No trimming or calibration is required.
4. The analog input can be taken to 150 mV below GND for true bipolar operation.
5. The specified voltage reference range on REFIN is from 2.5 V to the supply voltage, VDD.
