AD7740YRT-REEL7

Overview

The AD7740YRT-REEL7 is a low-cost, ultrasmall synchronous Voltage-to-Frequency Converter (VFC) from Analog Devices. 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 bipolar capability down to -150 mV without a charge pump. The full-scale output frequency is determined by the external clock on CLKIN, supporting up to 1 MHz. Integral Nonlinearity is specified at ±0.012% of span in unbuffered mode.

Feature Summary

• Synchronous operation where the full-scale output frequency is defined by the external system clock signal applied to the CLKIN pin.
• Selectable high impedance buffered input mode via the BUF pin, providing minimal loading on the source signal.
• True bipolar input capability allowing the VIN pin to accept voltages as low as -150 mV below ground without requiring a charge pump.
• Integrated automatic power-down function that activates when the clock input remains inactive for approximately 1 ms.

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 the specific suffix REEL7 corresponds to the tape and reel packaging format required for automated assembly processes. Confirm that the Y grade designation meets the automotive temperature range requirements of -40°C to +105°C for your specific deployment environment. Ensure the ordering documentation matches the exact part number to avoid discrepancies in package type or electrical specifications.

Selection Notes

Select this component when space constraints necessitate an 8-lead SOT-23 or MSOP package. Choose the buffered mode for high source impedance signals to minimize current draw. Utilize the unbuffered mode if negative input voltages relative to ground are expected. Consider the internal 2.5 V reference for ratiometric applications to simplify external component count.

Part Context

This device belongs to the AD7740 series of voltage-to-frequency converters designed for cost-sensitive and space-constrained applications. It utilizes a charge-balance conversion technique to translate analog input voltages into a digital pulse train. The synchronous architecture ensures stability by relying on an external clock rather than internal timing components, distinguishing it from asynchronous VFC designs.

Replacement Considerations

The AD7740KRMZ-REEL7 is a commercially graded alternative within the same family, guaranteed for operation from 0°C to +85°C instead of the automotive range. Verify that the lower temperature limit of the K grade is acceptable for your application before substitution.

FAQ

How is the output frequency synchronized?

The output frequency is synchronized to the rising edge of the master clock signal applied to the CLKIN pin. The full-scale frequency range is directly proportional to this input clock frequency.

What is the purpose of the BUF pin?

The BUF pin selects between buffered and unbuffered input modes. When tied high, it enables a high-impedance buffered input; when tied low, it allows the input to go below ground potential.

Can the internal reference be overridden?

Yes, an external precision reference can be connected to the REFIN/OUT pin to overdrive the internal 2.5 V bandgap reference, provided the external source can sink and source sufficient current.