AD7740KRMZ

Overview

The AD7740KRMZ is a low-cost, ultrasmall synchronous Voltage-to-Frequency Converter (VFC) manufactured by Analog Devices Inc. It operates from a single 3.0 V to 3.6 V or 4.75 V to 5.25 V supply, 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 an external clock on the CLKIN pin, supporting frequencies up to 1 MHz. It is available in an 8-lead MSOP package.

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 span.

Applications

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

Procurement Notes

Verify the specific grade suffix when ordering; the K variant denotes commercial temperature range while Y indicates automotive grade. Confirm package type matches design requirements as pinouts differ between SOT-23 and MSOP. Ensure supply voltage aligns with selected operating range. Check RoHS compliance status if required by assembly specifications. Validate clock source compatibility with CMOS logic levels.

Selection Notes

Choose the K grade for commercial environments ranging from 0°C to +85°C. Select the Y grade for automotive applications requiring operation from -40°C to +105°C. Consider the buffered mode for high-impedance sources to minimize loading effects. Evaluate power consumption differences between buffered and unbuffered modes based on system battery constraints. Ensure the external clock frequency supports the desired resolution and conversion speed.

Part Context

This component belongs to the AD7740 family of synchronous voltage-to-frequency converters. It utilizes charge-balance conversion technology to translate analog input voltages into a digital pulse train. The design emphasizes space savings and cost reduction compared to traditional ADC solutions. It integrates a precision reference and modulator within a compact footprint suitable for portable and industrial instrumentation.

Replacement Considerations

Direct substitutes include other parts within the AD7740 series such as the AD7740YRTZ for different packaging options. Verify thermal performance and pinout compatibility before swapping packages. Cross-reference specifications for integral nonlinearity and offset error if higher precision is required. Ensure replacement parts support the same clock frequency range and supply voltage conditions.