THS4541: Assistance with FDA Bessel MFB LPF Design

Tool/software:

I am designing a 2nd-order Bessel MFB low-pass filter using the THS4541 with the following specifications:

• Passband: DC to 100 kHz with minimal insertion loss and group delay
• Stopband: 1 MHz
• Input/Output Impedance: input is connected to a low-impedance buffer, output is driving approximately a 1 kΩ load
• Power Supply: Single 3.3V

I used TINA-TI to analyze the response and group delay, and I obtained the following results:

• Group delay: Between 720 ns and 734 ns
• Insertion loss: 0.24 dB at 100 kHz, increasing to 18 dB at 1 MHz (the best loss I could achieve)

Group delay is between 720 and 734nsec

I have two main concerns:

1. Could someone assist me in performing a phase stability analysis?
2. Is there a way to improve stopband attenuation beyond 18 dB at 1 MHz without increasing the filter stage count?

Any insights or recommendations would be greatly appreciated.

Thanks!

Nir