6.3 Feature Description

6.3.1 Analog Input

As shown in Figure 6-1, the input of the AMC0106M25 is a fully differential, switched-capacitor circuit with a

dynamic input impedance of 27.5kΩ at 20MHz.

The sampling capacitor is continuously charged and discharged with a frequency of fCLK. With the S1 switches

closed, CIND charges to the voltage difference across VINP and VINN. For the discharge phase, both S1 switches

open first and then both S2 switches close. CIND discharges to approximately AGND + 0.8V during this phase.

AGND

INP

INN

CINN = 3pF

AGND

CINN = 3pF

270

270

CIND = 1.8pF

AGND

AGND

AGND + 0.8V

AGND + 0.8V

S1

S1

S2

S2

RIN = 27.5k

INP

INN

3pF

AGND

3pF

AGND

Equivalent circuit at

fCLK = 20 MHz

RIN =

(fCLK x CIND)

1

Figure 6-1. Equivalent Input Circuit

The analog input range is tailored to directly accommodate a voltage drop across a shunt resistor used for

current sensing. There are two restrictions on the analog input signals (INP and INN). First, if the input voltage

exceeds the input range specified in the Absolute Maximum Ratings table, limit the input current to the absolute

maximum value because the electrostatic discharge (ESD) protection turns on. Second, the linearity and noise

performance of the device are specified only when the differential analog input voltage remains within the

specified VFSR and VCM ranges. VFSR is the linear full-scale range and VCM is the input common-mode voltage

range.

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AMC0106M25

SBASAX1A – AUGUST 2024 – REVISED JULY 2025

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