7.2.1 Design Requirements

Table 7-1 lists the parameters for this typical application.

Table 7-1. Design Requirements

PARAMETER

VALUE

Supply voltage

3.3 V or 5 V

Voltage drop across the shunt for a linear response (VSHUNT)

±250 mV (maximum)

7.2.2 Detailed Design Procedure

The AMC3301 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 of the AMC3301 (INN). If a four-pin shunt is used, the inputs of the AMC3301 are connected to the inner

leads and HGND is connected to one of the outer shunt 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.

7.2.2.1 Shunt Resistor Sizing

Use Ohm's Law to calculate the voltage drop across the shunt resistor (VSHUNT) for the desired measured

current: VSHUNT = I × RSHUNT .

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

voltage range: |VSHUNT| ≤ |VFSR|

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

a clipping output: |VSHUNT| ≤ |VClipping|

7.2.2.2 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 7-2 achieves excellent performance.

10 Ÿ

10 Ÿ

10 nF

DCDC_OUT

DCDC_HGND

HLDO_IN

HLDO_OUT

HGND

INP

INN

NC

AMC3301

DCDC_IN

LDO_OUT

VDD

OUTP

OUTN

GND

DIAG

DCDC_GND

Figure 7-2. Differential Input Filter

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AMC3301

SBAS917C – AUGUST 2019 – REVISED MAY 2025

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