A differential input signal of 0V ideally produces a stream of ones and zeros that are high 50% of the time. A differential input of 1V 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 –1V produces a stream of ones and zeros that are high 10.94% of the time. With 16 bits of resolution, that percentage ideally corresponds to code 7168. These input voltages are also the specified linear range of the AMC0386-Q1. If the input voltage value exceeds this range, the output of the modulator shows increasing nonlinear behavior as the quantization noise increases. The modulator output clips with a constant stream of zeros at an input ≤–1.28V or with a constant stream of ones at an input ≥1.28V. In this case, however, the AMC0386-Q1 generates a single 1 or 0 every 128 clock cycles to indicate proper device function. A single 1 is generated if the input is at negative fullscale and a 0 is generated if the input is at positive fullscale. See the Output Behavior in Case of a Fullscale Input section for more details. Figure 6-3 shows the input voltage versus the output modulator signal.

Figure 6-3 Modulator Output vs Analog Input

Calculate the density of ones in the output bitstream with Equation 1 for any input voltage V_IN = (V_SNSP – V_SNSN) value. The only exception is a fullscale input signal. See the Output Behavior in Case of a Fullscale Input section.