8.2.1 Design Requirements

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

Table 8-1. Design Requirements

PARAMETER

VALUE

Supply voltage

3.3 V or 5 V

±50 mV (maximum)

8.2.2 Detailed Design Procedure

The AMC3302-Q1 requires a single 3.3-V or 5-V supply on its low side. The high-side supply is internally

generated by an integrated DC/DC converter, as explained in the Isolated DC/DC Converter section.

The ground reference (HGND) is derived from the terminal of the shunt resistor that is connected to the negative

input (INN) of the AMC3302-Q1. If a four-pin shunt is used, the inputs of the device are connected to the inner

leads and HGND is connected to one of the outer leads. To minimize offset and improve accuracy, set the

ground connection to a separate trace that connects directly to the shunt resistor rather than shorting HGND 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 to choose the proper 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 Ÿ

10 Ÿ

10 nF

DCDC_OUT

DCDC_HGND

HLDO_IN

HLDO_OUT

HGND

INP

INN

NC

AMC3302-Q1

DCDC_IN

LDO_OUT

VDD

OUTP

OUTN

GND

DIAG

DCDC_GND

Figure 8-2. Differential Input Filter

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AMC3302-Q1

SBASA84A – FEBRUARY 2021 – REVISED JULY 2021

Copyright © 2021 Texas Instruments Incorporated

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