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 250 mV (for the AMC1304x25) or 50 mV (for the AMC1304x05) produces a stream of ones and zeros that are high 90% of the time. A differential input of –250 mV (–50 mV for the AMC1304x05) produces a stream of ones and zeros that are high 10% of the time. These input voltages are also the specified linear ranges of the different AMC1304 versions with performance as specified in this data sheet. If the input voltage value exceeds these ranges, the output of the modulator shows non-linear behavior when the quantization noise increases. The output of the modulator clips with a stream of only zeros with an input less than or equal to –312.5 mV (–62.5 mV for the AMC1304x05) or with a stream of only ones with an input greater than or equal to 312.5 mV (62.5 mV for the AMC1304x05). In this case, however, the AMC1304 generates a single 1 (if the input is at negative full-scale) or 0 every 128 clock cycles to indicate proper device function (see the Fail-Safe Output section for more details). The input voltage versus the output modulator signal is shown in Figure 50.
The density of ones in the output bit-stream for any input voltage value (with the exception of a full-scale input signal, as described in the Output Behavior in Case of a Full-Scale Input section) can be calculated using Equation 1:
The AMC1304 system clock is typically 20 MHz and is provided externally at the CLKIN pin. Data are synchronously provided at 20 MHz at the DOUT pin. Data change at the CLKIN falling edge. For more details, see the Switching Characteristics table.