A Pulse Slicer is a variation of the Zero Crossing Detector and is used to detect the zero crossings on an input signal with a varying baseline level. This circuit works best with symmetrical waveforms. The RC network of R₁ and C₁ establishes an mean reference voltage V_REF, which tracks the mean amplitude of the V_IN signal. The non-inverting input is directly connected to V_REF through R2. R2 and R3 are used to produce hysteresis to keep transitions free of spurious toggles. The time constant is a tradeoff between long-term symmetry and response time to changes in amplitude.

If the waveform is data, it is recommended that the data be encoded in NRZ (Non-Return to Zero) format to maintain proper average baseline. Asymmetrical inputs may suffer from timing distortions caused by the changing V_REF average voltage.

Figure 9-18 Pulse Slicer

For this design, follow these design requirements:

• The RC constant value (R₂ and C₁) must support the targeted data rate to maintain a valid tripping threshold.
• The hysteresis introduced with R₂ and R₄₃ helps to avoid spurious output toggles.

The TLV182x may also be used, but with the addition of a pull-up resistor on the output (not shown for clarity).

Figure 9-19 shows the results of a 9600 baud data signal riding on a varying baseline.

Figure 9-19 Pulse Slicer Waveforms