MAX7420CUA+

Overview

The MAX7420CUA+ is a fifth-order, low-pass switched-capacitor filter featuring a Butterworth response for a maximally flat passband. It operates from a single +5V supply with a typical current draw of 3mA and supports corner frequencies from 1Hz to 45kHz via a 100:1 clock-to-corner ratio. The device includes a shutdown mode reducing current to 0.2μA, an offset adjust pin, and low output offset of ±4mV. Housed in an 8-pin μMAX package, it functions within a temperature range of 0°C to +70°C.

Feature Summary

• Butterworth filter response providing a maximally flat passband
• Clock-tunable corner frequency ranging from 1Hz to 45kHz
• Low-power shutdown mode with 0.2μA standby current
• Single-supply operation at +5V

Applications

• ADC anti-aliasing
• DAC postfiltering
• CT2 base stations
• Speech processing

Procurement Notes

Verify the specific suffix 'CUA+' against the manufacturer's official documentation to confirm the commercial temperature range (0°C to +70°C) and RoHS compliance status. Ensure the ordering code matches the exact package type and revision required for the design. Cross-reference the component marking with the datasheet to prevent counterfeit substitution.

Selection Notes

Select the MAX7420CUA+ when a maximally flat passband response is required for instrumentation applications. This part is designed for single +5V systems; verify that the application voltage does not exceed the specified maximums. Consider the external clock or internal oscillator requirements based on the desired corner frequency precision and available system timing resources.

Part Context

This component belongs to the MAX7418–MAX7425 family of fifth-order, low-pass switched-capacitor filters. While other members offer elliptic or Bessel responses, the MAX7420 specifically provides the Butterworth characteristic. It shares the same physical footprint and basic interface as its siblings but differs in frequency response characteristics and internal circuit topology.

Replacement Considerations

Direct substitutes within the same series include the MAX7424EUA for extended temperature ranges (-40°C to +85°C). Other models like the MAX7418 or MAX7419 provide different filter responses (elliptic or Bessel) and should only be considered if the specific Butterworth response is not strictly required.

FAQ

How is the corner frequency determined?

The corner frequency is set by the clock frequency using a fixed 100:1 ratio (fC = fCLK / 100). It can be controlled by an external clock source or an internal oscillator defined by an external capacitor.

What is the function of the OS pin?

The Offset Adjust (OS) pin allows for adjustment of the DC output level. It can be connected to the COM pin for no adjustment or driven by an external bias voltage to shift the output DC level.

How does the shutdown mode work?

Driving the SHDN pin low activates the shutdown mode, reducing the supply current to 0.2μA and placing the output in a high-impedance state. Driving SHDN high or connecting it to VDD returns the device to normal operation.