8th-Order, Lowpass, Elliptic, Switched-Capacitor Filters

 

Part Number	Replacement	Explanation

Description

Create a design and simulate using EE-Sim^® tools:

The MAX293/MAX294/MAX297 are easy-to-use, 8th-order, lowpass, elliptic, switched-capacitor filters that can be set up with corner frequencies from 0.1Hz to 25kHz (MAX293/MAX294) or from 0.1Hz to 50kHz (MAX297).

The MAX293/MAX297's 1.5 transition ratio provides sharp rolloff and -80dB of stopband rejection. The MAX294's 1.2 transition ratio provides the steepest rolloff and -58dB of stopband rejection. All three filters have fixed responses, so the design task is limited to selecting the clock frequency that controls the filter's corner frequency.

An external capacitor is used to generate a clock using the internal oscillator, or an external clock signal can be used. An uncommitted op amp (noninverting input grounded) is provided for building a continuous-time lowpass filter for post-filtering or anti-aliasing. Steep rolloff and high order make these filters ideal for anti-aliasing applications that require maximum bandwidth, and for communication applications that require filtering signals in close proximity within the frequency domain.

The MAX293/MAX294/MAX297 are available in 8-pin DIP and 16-pin wide SO packages, delivering aggressive performance from a tiny area.

MAX293, MAX294, MAX297: Typical Operating Circuit Enlarge+

Key Features

• 8th-Order Lowpass Elliptic Filters
• Clock-Tunable Corner-Frequency Range:
  • 0.1Hz to 25kHz (MAX293/MAX294)
  • 0.1Hz to 50kHz (MAX297)
• No External Resistors or Capacitors Required
• Internal or External Clock
• Clock to Corner Frequency Ratio
  • 100:1 (MAX293/MAX294)
  • 50:1 (MAX297)
• Operate with a Single +5V Supply or Dual ±5V Supplies
• Uncommitted Op Amp for Anti-Aliasing or Clock-Noise Filtering
• 8-Pin DIP and 16-Pin Wide SO Packages

Applications/Uses

• Anti-Aliasing
• DAC Post-Filtering
• Data-Acquisition Systems
• Voice/Data Signal Filtering