Analog Devices Inc./Maxim Integrated MAX7480ESA+T

Introduction to MAX7480ESA+T 8th-Order Lowpass Filter

The MAX7480ESA+T, from Analog Devices Inc./Maxim Integrated, is an advanced integrated circuit specifically designed for precise and flexible low-frequency signal filtering. This device implements an 8th-order, lowpass Butterworth switched-capacitor filter in a compact 8-pin SOIC or DIP package, targeting precision analog signal-conditioning tasks such as ADC anti-aliasing and post-DAC (digital-to-analog converter) filtering. Its maximally flat passband and highly predictable frequency response make it a prime candidate for applications that demand both accuracy and ease of implementation in environments powered by a single +5V rail.

Design Structure and Operating Mechanism of MAX7480ESA+T

At the heart of the MAX7480ESA+T lies a switched-capacitor design, emulating the characteristics of a passive ladder network for superior component tolerance and stability. Unlike cascaded biquad structures commonly employed in switched-capacitor filters, which can suffer from concentrated errors if stage quality factors (Q) are high, the ladder emulation distributes sensitivity, ensuring that any variation in internal components results in a minor global effect rather than significant local misbehavior.

The filter’s 8th-order Butterworth response is realized using switched-capacitor integrators, summing, and scaling blocks. Importantly, the filter’s passband is designed to be maximally flat—a hallmark of the Butterworth topology—avoiding ripple and providing consistent DC-to-cutoff frequency gain. The filter operates at a fixed 100:1 clock-to-corner frequency ratio, with the corner frequency set by the applied clock or internal oscillator frequency.

Important Electrical Specifications and Performance Details of MAX7480ESA+T

Designed for single-supply operation at +5V, the MAX7480ESA+T draws a modest 2.9mA during normal operation and drops to a mere 0.2μA in shutdown mode, making it highly suitable for portable and low-power systems. The device tolerates a supply range from –0.3V to +6V, and operates reliably across an industrial temperature span (–40°C to +85°C).

The filter supports corner frequencies from as low as 1Hz up to 2kHz, dictated by the user’s choice of clock frequency (with fC = fCLK/100). Input and output voltage offsets are tightly controlled (±5mV typical), and harmonic distortion is extremely low (–73dB THD+N). The filter output remains stable when loaded with 10kΩ || 50pF, which closely aligns with many ADC and DAC interfacing requirements.

The MAX7480ESA+T is robustly protected, with a 1-second output short-circuit duration and an absolute maximum ratings envelope that supports soldering and harsh storage conditions. Its low output offset and high signal fidelity equip it for sensitive measurement and control systems.

Clock Configuration and Frequency Adjustment with MAX7480ESA+T

The MAX7480ESA+T offers engineers a choice between external and internal clocking:

For external clocking, the device expects a CMOS-level clock (40–60% duty cycle) applied to the CLK pin, with the corner frequency given directly by fC = fCLK/100. This option facilitates synchronization with other digital elements—an essential feature for anti-aliasing in data acquisition systems.

Internal clocking is achieved by connecting a capacitor (COSC) from CLK to ground, with the internal oscillator frequency fOSC (in kHz) calculated as fOSC ≈ 53,000/COSC (pF). This method provides a straightforward, flexible means for standalone operation when less stringent synchronization is necessary.

The filter’s input impedance is inversely proportional to clock frequency, approximated by ZIN ≈ 1/(fCLK × 2.31pF). As a rule of thumb, driving sources should present an impedance less than one-tenth of the filter’s calculated average input impedance to avoid gain errors and preserve accuracy.

Use Cases of MAX7480ESA+T for Signal Processing Applications

The MAX7480ESA+T is particularly valuable in roles such as:

ADC anti-aliasing: By configuring the filter to a corner frequency just below half the ADC’s sample clock, engineers can significantly attenuate unwanted high-frequency content, suppressing aliasing artifacts.

Post-DAC filtering: Smoothing the stepped output from a DAC with the MAX7480ESA+T yields precise, low-distortion analog waveforms free from digital quantization noise above the passband.

Instrumentation: Any application demanding rigorous passband accuracy, such as process control or sensor data filtering, benefits from the Butterworth response and minimal passband ripple.

In practical use, it is essential to synchronize filter and data converter clocks to avoid intermodulation and unwanted frequencies within the passband. The high ratio between clock and cutoff frequency also means simple RC networks can be used at the input or output for anti-aliasing or further clock feedthrough reduction, respectively.

Power Supply, Control Methods, and Signal Connections for MAX7480ESA+T

The MAX7480ESA+T is powered by a single +5V supply (bypassed with a 0.1μF capacitor). The device may also be operated with dual supplies (±2.5V) for systems that require a wider input/output signal range; in such scenarios, the COM pin is set at system ground, enabling seamless integration without altering filter behavior.

Shutdown is controlled via the SHDN pin. Pulling SHDN low reduces current consumption to 0.2μA and places the output in high impedance, an advantage for battery-powered or multiplexed-channel designs.

A clever offset adjustment feature enables DC shifting or common-mode adjustment without additional complex circuitry: Connecting OS to COM biases the output at mid-supply, but feeding a different bias through OS allows precision DC level tuning to interface with other analog subsystem blocks.

Alternative or Substitute Options for MAX7480ESA+T

Engineers seeking functionally similar alternatives to the MAX7480ESA+T within the family of integrated switched-capacitor lowpass filters may consider the following approaches:

Other 8th-order, lowpass, Butterworth switched-capacitor filters from Analog Devices Inc./Maxim Integrated, such as the MAX7400–MAX7490 series, with variations in cutoff frequency, response type (e.g., Bessel, elliptic), or operating voltage.

For systems requiring higher corner frequencies or specialized performance characteristics (such as sharper rolloff or different shapes within the passband), consult the MAX291–MAX297 series by Maxim Integrated, which offer distinct filter responses and frequency ranges.

Design transitions to alternative brands must ensure matching in filter order, topology, supply voltage, clocking interface, and pin configuration to minimize redesign efforts and preserve circuit performance equivalence.

When evaluating replacements, particular attention should be paid to order, response, signal range, supply requirements, and package compatibility, as mismatches may affect both functional integrity and ease of integration.

Conclusion

: Engineering value and selection considerations for the MAX7480ESA+T

The MAX7480ESA+T stands out as a highly reliable and energy-efficient solution for lowpass signal conditioning in applications where passband flatness, predictable tuning, and simple single-rail operation are critical. Its flexible clocking design, integrated shutdown function, and Butterworth response uniquely tailor it for modern ADC and DAC interfacing as well as demanding instrumentation environments. Competitive models within the same manufacturer’s portfolio or compatible designs from other brands provide further choice, enabling robust continuity in design and procurement. By closely matching performance and packaging requirements, engineers and purchasing professionals can confidently integrate the MAX7480ESA+T or its equivalents into their next-generation analog signal processing systems.