8.2.1 Design Requirements

Table 8-1 lists the parameters for this typical application.

Table 8-1. Design Requirements

PARAMETER

VALUE

High-side supply voltage

3.3 V or 5 V

Low-side supply voltage

3.3 V or 5 V

Voltage drop across RSHUNT for a linear response

±50 mV (maximum)

3 µs (maximum)

8.2.2 Detailed Design Procedure

In Figure 8-1, the high-side power supply (VDD1) for the AMC1202 is derived from the floating power supply of

the upper gate driver.

The floating ground reference (GND1) is derived from the end of the shunt resistor that is connected to the

negative input of the AMC1202 (INN). If a four-pin shunt is used, the inputs of the AMC1202 are connected to

the inner leads and GND1 is connected to the outer lead on the INN-side of the shunt. To minimize offset and

improve accuracy, route the ground connection as a separate trace that connects directly to the shunt resistor

rather than shorting GND1 to INN directly at the input to the device. See the Layout section for more details.

8.2.2.1 Shunt Resistor Sizing

Consider the following two restrictions when selecting the value of the shunt resistor, RSHUNT:

• The voltage drop caused by the nominal current range must not exceed the recommended differential input

• The voltage drop caused by the maximum allowed overcurrent must not exceed the input voltage that causes

8.2.2.2 Input Filter Design

TI recommends placing an RC-filter in front of the isolated amplifier to improve signal-to-noise performance of

the signal path. Design the input filter such that:

• The cutoff frequency of the filter is at least one order of magnitude lower than the sampling frequency

(20 MHz) of the ΔΣ modulator

• The input bias current does not generate significant voltage drop across the DC impedance of the input filter

• The impedances measured from the analog inputs are equal

For most applications, the structure shown in Figure 8-2 achieves excellent performance.

10

10

10 nF

VDD1

GND1

INP

INN

AMC1202

VDD2

OUTP

OUTN

GND2

Figure 8-2. Differential Input Filter

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AMC1202

SBASAB8 – MAY 2021

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