MAX7427EPA+

Overview

The MAX7427EPA+ is a 5th-order, lowpass, elliptic switched-capacitor filter designed for single-supply operation at +3V. It features a clock-to-corner frequency ratio of 100:1, allowing corner frequencies from 0.001kHz to 12kHz. The device provides -79dB typical THD+N and 37dB stopband rejection with a transition ratio of 1.25. Operating current is 0.8mA, reducing to 0.2µA in shutdown mode. It includes an offset-adjust pin and operates within a temperature range of -40°C to +85°C.

Feature Summary

• Provides sharp rolloff with 37dB stopband rejection using a fixed elliptic response.
• Supports both self-clocking via external capacitor and external clock inputs.
• Includes a dedicated offset-adjust pin for DC output level tuning.
• Features a low-power shutdown mode that reduces supply current significantly.

Applications

• ADC anti-aliasing
• Post-DAC filtering
• Speech processing

Procurement Notes

Verify the component is the MAX7427 variant rated for +3V operation, distinct from the MAX7426 which requires +5V. Confirm the 'E' suffix indicates the extended industrial temperature range (-40°C to +85°C) and the 'PA+' denotes the PDIP-8 package with lead-free compliance. Check for obsolescence status as older Maxim products may be discontinued.

Selection Notes

Select this component when a steep roll-off is required for anti-aliasing or post-DAC applications in low-power systems. Ensure the system operates on a single +3V supply. Verify that the required corner frequency falls within the 1Hz to 12kHz range achievable with the 100:1 clock ratio. Consider the MAX7426 if a +5V supply is available instead.

Part Context

This part belongs to the MAX7426/MAX7427 family of 5th-order elliptic switched-capacitor filters. The MAX7427 specifically targets +3V single-supply applications, while the MAX7426 is designed for +5V systems. Both share identical filter characteristics and pinouts, differing primarily in operating voltage specifications.

Replacement Considerations

MAX7426EPA+ (Requires +5V supply)

FAQ

How is the corner frequency determined?

The corner frequency is set by the clock frequency using a fixed 100:1 ratio. It can be controlled via an external clock source or an internal oscillator defined by a capacitor connected to the CLK pin.

What is the function of the OS pin?

The OS (Offset Adjust) pin allows for adjustment of the DC output level. It should be connected to COM if no offset adjustment is needed, or biased with a resistive divider for DC level shifting.

How does the shutdown mode work?

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