AD7740KRM-REEL7

Overview

The AD7740KRM-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 in unbuffered mode. The device features an internal 2.5 V bandgap reference and supports a maximum input frequency of 1 MHz. Integral Nonlinearity is specified at ±0.012% of span in unbuffered mode with a 1 MHz clock. The part is housed in an 8-lead MSOP package and is guaranteed for operation from 0 °C to +85 °C.

Feature Summary

• Synchronous operation where the full-scale output frequency is determined by the external system clock signal on the CLKIN pin.
• True bipolar input capability allowing the analog voltage to go -150 mV below ground without requiring a charge pump.
• Selectable high impedance buffered input mode to minimize loading on the source signal.
• Automatic power-down function activated when the clock input remains inactive low.

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 that the specific ordering suffix matches the required tape and reel packaging configuration. Confirm the temperature grade corresponds to the intended operating environment, as commercial and automotive grades have distinct thermal specifications. Ensure the component is sourced from authorized distributors to guarantee authenticity and traceability. Check for RoHS compliance status if environmental regulations apply to the final assembly.

Selection Notes

Select this component for designs requiring a compact, single-channel VFC with minimal external passive components. The choice between buffered and unbuffered modes depends on the source impedance and whether negative input voltages are necessary. Consider the stability of the external clock source, as it directly defines the transfer function accuracy. Evaluate power consumption requirements against the available supply voltage range of 3 V or 5 V.

Part Context

This component belongs to the AD7740 family of synchronous voltage-to-frequency converters. It is designed to replace asynchronous VFCs that rely on external capacitors for frequency setting, offering superior stability through clock synchronization. The K-grade variant specifically targets commercial temperature ranges, providing a cost-effective solution for space-constrained analog-to-digital conversion tasks.

Replacement Considerations

Direct substitutes within the same package and specification include the AD7740KRMZ and AD7740KRMZ-REEL. Verify pinout compatibility between MSOP variants before substitution.

FAQ

How is the full-scale output frequency determined?

The full-scale output frequency is set synchronously by the clock signal applied to the CLKIN pin, rather than by external resistors or capacitors.

Can the input voltage be negative?

Yes, in unbuffered mode, the VIN pin can accept signals down to -0.15 V relative to ground.

What happens if the clock signal stops?

If the CLKIN pin is held inactive low for approximately 1 ms, the device automatically enters a low-power shutdown mode.