Package and board-fit — 16-QSOP, tube delivery
The MAX7491CEE+: The tube packaging means no moisture-sensitive-device (MSD) floor-life clock starts when you open the tube; store the reels dry is not a concern here, just keep the tube sealed against dust. Surface-mount assembly on a standard 0.050-inch pitch SSOP footprint. The 16-pin body is compact enough for space-constrained mixed-signal boards but leaves room for decoupling caps at the supply pins.
Filter core — 40 kHz switched-capacitor, dual 2nd-order
A universal switched-capacitor filter with a 40 kHz center/cutoff frequency and 2nd-order response. The universal topology means it can be configured as low-pass, high-pass, bandpass, or notch by pin-strapping the feedback paths — no external resistors or capacitors set the frequency, only the clock input and the internal switched-capacitor network. Two independent filters on one die — useful for stereo audio anti-aliasing, dual-channel data-acquisition reconstruction, or cascading into a 4th-order response. The 40 kHz cutoff places it in the audio band and low-frequency instrumentation range; it will alias above 40 kHz unless the input is band-limited before the filter. The switched-capacitor architecture draws clock-dependent current; at 40 kHz the dynamic current is modest, but the clock feedthrough at the output needs a post-filter cap (typically 100 pF) to suppress the switching ripple.
If you need a backup, the functional equivalent would be a different package or pinout; a board spin would be required. Stock the last-time-buy quantity if the design is long-lived.