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 1 V 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. A differential input of –1 V produces a stream of ones and zeros that are high 10% of the time and ideally results in code 6553 with 16-bit resolution. These input voltages are also the specified linear range of the AMC3336. 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 stream of only zeros with an input less than or equal to –1.25 V or with a stream of only ones with an input greater than or equal to 1.25 V. In this case, however, the AMC3336 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 Analog Input vs Modulator Output

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

Equation 1.