7.3 Feature Description

The differential analog input of the AMC1100 is a switched-capacitor circuit based on a second-order modulator stage that digitizes the input signal into a 1-bit output stream. The device compares the differential input signal (V_IN = VINP – VINN) against the internal reference of 2.5 V using internal capacitors that are continuously charged and discharged with a typical frequency of 10 MHz. With the S1 switches closed, C_IND charges to the voltage difference across VINP and VINN. For the discharge phase, both S1 switches open first and then both S2 switches close. C_IND discharges to approximately GND1 + 0.8 V during this phase. Figure 33 shows the simplified equivalent input circuitry.

Figure 33. Equivalent Input Circuit

The analog input range is tailored to directly accommodate a voltage drop across a shunt resistor used for current sensing. However, there are two restrictions on the analog input signals, VINP and VINN. If the input voltage exceeds the range GND1 – 0.5 V to VDD1 + 0.5 V, the input current must be limited to 10 mA to protect the implemented input protection diodes from damage. In addition, the device linearity and noise performance are ensured only when the differential analog input voltage remains within ±250 mV.