AMC1303E0510 Datasheet, PDF (21/40 Pages) Texas Instruments – Small, High-Precision, Reinforced Isolated Delta-Sigma Modulators with Internal Clock

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AMC1303E0510, AMC1303M0510, AMC1303E0520, AMC1303M0520
AMC1303E2510, AMC1303M2510, AMC1303E2520, AMC1303M2520
SBAS771 – JUNE 2017
Feature Description (continued)
8.3.4 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 (for the AMC1303x25x) or 50 mV (for the AMC1303x05x) produces a stream of ones
and zeros that are high 89.06% of the time. With 16 bits of resolution on the decimation filter, that percentage
ideally corresponds to code 58368. A differential input of –250 mV (–50 mV for the AMC1303x05x) produces a
stream of ones and zeros that are high 10.94% of the time and ideally results in code 7168 with a 16-bit
resolution decimation filter. These input voltages are also the specified linear ranges of the different AMC1303
versions with performance as specified in this document. If the input voltage value exceeds these ranges, the
output of the modulator shows nonlinear behavior where 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 (–64 mV for the
AMC1303x05x) or with a stream of only ones with an input greater than or equal to 320 mV (64 mV for the
AMC1303x05x). In this case, however, the AMC1303 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).
Figure 41 shows the input voltage versus the output modulator signal.
Modulator Output
+FS (Analog Input)
-FS (Analog Input)
Analog Input
Figure 41. Analog Input versus AMC1303 Modulator Output
Equation 1 calculates 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):
V_IN V_Clipping
2 u V_Clipping
(1)
The AMC1303 internally generates the clock signal required for the modulator. This clock is provided externally
at the CLKOUT pin on AMC1303Mx devices only. For more details, see the Switching Characteristics section.
8.3.5 Manchester Coding Feature
The AMC1303Ex offers the IEEE 802.3-compliant Manchester coding feature that generates at least one
transition per bit to support clock signal recovery from the bitstream. A Manchester coded bitstream is free of dc
components. The Manchester coding combines the clock and data information using exclusive or (XOR) logical
operation. Figure 42 shows the resulting bitstream.
Clock
Uncoded
Bitstream
Machester
Coded
Bitstream
101011100110001
Figure 42. Manchester Coded Output of the AMC1303Ex
Copyright © 2017, Texas Instruments Incorporated
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