An input signal of 0V ideally produces a stream of ones and zeros that are high 50% of the time. An input of 1V produces a stream of ones and zeros that are high 90% of the time. With 16 bits of resolution, that percentage ideally corresponds to code 58982. An input of –1V produces a stream of ones and zeros that are high 10% of the time. With 16 bits of resolution, that percentage ideally corresponds to code 6554. These input voltages are also the specified linear range of the AMC0386. 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 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 7-4 shows the input voltage versus the output modulator signal.

Figure 7-4 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.