AD7740YRMZ

Overview

The AD7740YRMZ is a low-cost, ultrasmall synchronous Voltage-to-Frequency Converter (VFC) from Analog Devices. It operates on a single supply of 3.0 V to 3.6 V or 4.75 V to 5.25 V, consuming typically 0.9 mA. The device features an internal 2.5 V bandgap reference and accepts analog inputs from 0 V to VREF, with true capability down to -150 mV without a charge pump. The full-scale output frequency is set by the external clock on the CLKIN pin, ranging up to 1 MHz. Integral Nonlinearity is specified at ±0.012% of span in unbuffered mode. It is housed in an 8-lead MSOP package and guaranteed for automotive temperature ranges of -40°C to +105°C.

Feature Summary

• Synchronous operation where the full-scale output frequency is determined by the external system clock signal applied to the CLKIN pin.
• Selectable high impedance buffered input mode via the BUF pin, allowing for very high source impedance tolerance.
• True bipolar input capability extending 150 mV below ground without requiring an external charge pump circuit.
• Minimal external component requirement as no resistors or capacitors are needed to set the output frequency range.

Applications

• Isolation of high common-mode voltages using opto-isolators
• Low-cost analog-to-digital conversion systems
• Battery monitoring circuits
• Automotive sensing applications

Procurement Notes

Verify that the specific part number suffix corresponds to the required operating temperature grade, as the Y designation indicates the automotive range of -40°C to +105°C. Confirm the package type matches the design footprint, specifically the 8-lead MSOP configuration. Ensure the power supply rails align with the specified 3.0 V to 3.6 V or 4.75 V to 5.25 V operational limits to maintain performance specifications.

Selection Notes

Select this component when space constraints require an ultrasmall package solution for voltage-to-frequency conversion. It is suitable for designs needing ratiometric operation using the internal 2.5 V reference or external overdrive. Consider the buffered versus unbuffered input modes based on source impedance requirements and whether negative input voltages relative to ground are necessary for the application signal range.

Part Context

This device belongs to the AD7740 family of synchronous voltage-to-frequency converters manufactured by Analog Devices. The family includes variants such as the K version for commercial temperatures and different packaging options like SOT-23. The AD7740 utilizes CMOS technology and charge-balance conversion techniques to achieve its performance characteristics within a compact form factor designed for cost-sensitive applications.

Replacement Considerations

The AD7740KRMZ serves as a commercial grade alternative within the same package. Other members of the AD7740 series may offer different temperature ratings or package styles but share the core functional architecture.

FAQ

How is the output frequency synchronized?

The output frequency is synchronous with the clock signal on the CLKIN pin, which can be provided by an external CMOS-compatible clock source or generated by an external crystal connected between CLKIN and CLKOUT.

What is the function of the BUF pin?

The BUF pin selects the input mode. When tied high, it enables a high impedance buffered mode with an input range of 0.1 V to VDD – 0.2 V. When tied low, it enables an unbuffered mode allowing inputs from -0.15 V to VDD + 0.15 V.