6.3 Feature Description

6.3.1 Analog Input

The high-impedance input buffer on the INP pin feeds a second-order, switched-capacitor, feed-forward ΔΣ

modulator. The modulator converts the analog signal into a bitstream that is transferred across the isolation

barrier, as described in the Isolation Channel Signal Transmission section.

For reduced offset and offset drift, the input buffer is chopper-stabilized with the chopping frequency set at

fCLKIN/16. Figure 6-1 shows the spur at 625kHz that is generated by the chopping frequency for a modulator

clock of 10MHz.

0.1

1

10

100

1000

Frequency (kHz)

-160

-140

-120

-100

-80

-60

-40

-20

0

G016

sinc3 filter, OSR = 1, fCLKIN = 10 MHz, fIN = 1 kHz

Figure 6-1. Quantization Noise Shaping

There are two restrictions on the analog input signal. First, if the input voltage exceeds the value specified

in the Absolute Maximum Ratings table, the input current must be limited to 10mA. This limitation is caused

by the device input electrostatic discharge (ESD) diodes turning on. Second, linearity and noise performance

are specified only when the input voltage is within the linear fullscale range (VFSR). VFSR is specified in the

Recommended Operating Conditions table.

AMC0136

SBASAZ0A – AUGUST 2024 – REVISED DECEMBER 2024

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