AMC131M01DFMR datasheet(69/81 Pages) TI

69 / 81 page

DVDD

Resonator and

Driver

LDO

DCDC_CAP

Rectifier

DGND

Control &

Serial

Interface

1.2-V

Reference

ADC

Gain &

Offset

Calibration

Phase

Shift &

Digital

Filter

Clock

Generation

HLDO_OUT

GND

SCLK

DOUT

DIN

DRDY

SYNC/RESET

CLKIN

Low side supply

(3.0 V to 5.5 V)

MCU

DCDC_OUT

DCDC_HGND

HGND

AIN0N

AIN0P

ISO GND

HLDO_IN

Ferrite

GPO

–

Figure 9-5. Current Sensing With the AMC131M01

9.2.2.1 Current Shunt Measurement

Figure 9-5 shows the analog front-end used for current measurement at the ADC channel 0, which consists of

the shunt resistor RSHUNT and an RC low-pass antialiasing filter (RFILT and CFILT).

For a shunt value of 200 μΩ and a maximum current of IMAX = 100 A, the maximum voltage drop across the

shunt is VSHUNT = RSHUNT × IMAX = 200 μΩ × ±100 A = ±20 mV.

To measure this shunt voltage, configure channel 0 of the AMC131M01 for gain = 32, which allows differential

voltage measurements of VIN1 = VAIN1P – VAIN1N = ±VREF / 8 = ±1.2 V / 32 = ±37.5 mV. The integrated charge

pump in the device allows voltage measurements 1.3 V below HGND while using a unipolar analog power

supply. This bipolar voltage measurement capability is important because one side of the shunt is connected to

the same ISO_GND potential as the HGND pin of the AMC131M01, which means that the absolute voltage that

the device must measure during the current measurement is up to 37.5 mV below HGND.

9.2.3 Application Curves

Electromagnetic interference (EMI) testing is common in many applications using the AMC131M01 to verify the

system does not produce radiated emissions that exceed the defined levels that can possibly negatively impact

other components or circuits in the system. See the Understanding electromagnetic compliance tests in digital

isolators white paper for a more in-depth description of EMI. The magnitude of acceptable radiation and testing

procedure for radiated emissions is put in place by the Comité International Spécial des Perturbations Radio,

also known as CISPR. Industrial applications measure according to the CISPR 11 standard, and automotive

applications measure to the CISPR 25 standard. For more information on the CISPR standards and the

respective magnitudes over frequency, see the An overview of radiated EMI specifications for power supplies

white paper.

Figure 9-6 and Figure 9-7 show the radiated emissions measurement for the AMC131M01 using the evaluation

module available at AMC131M03EVM.

The measurements were done following CISPR 11 requirements, that is in a in a semi-anechoic chamber using

a broadband antenna configured for horizontal and vertical polarizations with a 3-meter distance. The ADC is

receiving a continuous clock at the CLKIN pin, and is generating conversion results, however there is no SPI

communication while the emission profile is characterized.

www.ti.com

AMC131M01

SBASA57 – SEPTEMBER 2023

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