IN

Clipping

Clipping

V

V

2 V

u

ModulatorOutput

AnalogInput

+FS(AnalogInput)

-FS(AnalogInput)

16

AMC3306M25

SBAS996 – MAY 2020

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Feature Description (continued)

7.3.4 Digital Output

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 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 –250 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 AMC3306M25. 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 –320 mV or with a stream of

only ones with an input greater than or equal to 320 mV. In this case, however, the AMC3306M25 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 Output Behavior in Case of a Full-Scale Input section for more details). Figure 10 shows the input voltage

versus the output modulator signal.

Figure 10. Analog Input versus the AMC3306M25 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 Output Behavior in Case of a Full-Scale Input

section):

(1)

The AMC3306M25 system clock is provided externally at the CLKIN pin.