A differential input signal of 0 V ideally produces a stream of ones and zeros that are high 50% of the time. A differential input of 50 mV produces a stream of ones and zeros that are high 89.06% of the time. With 16 bits of resolution, that percentage ideally corresponds to code 58368. A differential input of –50 mV produces a stream of ones and zeros that are high 10.94% of the time and ideally results in code 7168 with 16-bit resolution. These input voltages are also the specified linear range of the AMC3306M05. If the input voltage value exceeds this range, the output of the modulator shows nonlinear behavior as the quantization noise increases. The output of the modulator clips with a constant stream of zeros with an input less than or equal to –64 mV or with a constant stream of ones with an input greater than or equal to 64 mV. In this case, however, the AMC3306M05 generates a single 1 (if the input is at negative full-scale) or 0 (if the input is at positive full-scale) every 128 clock cycles to indicate proper device function (see the Section 7.3.4.1 section for more details). Figure 7-4 shows the input voltage versus the output modulator signal.

Figure 7-4 AMC3306M05 Modulator Output vs Analog Input

The density of ones in the output bitstream can be calculated using Equation 1 for any input voltage value with the exception of a full-scale input signal, as described in Section 7.3.4.1:

Equation 1.