Reinforced Isolated Current-Sense Amplifier with Precision ±250-mV Input, Differential output & Integrated DC/DC Converter

This isolated single-supply bidirectional current sensing project can accurately measure load currents from –2A to 2A. The linear range of the input is from –250mV to 250mV with a differential output range of –2.05V to 2.05V. The gain of the circuit is fixed at 8.2V/V.  The project is based on AMC3301 chip which has a fully integrated, isolated DC/DC converter that allows single-supply operation from the low side of the device. The integrated DC-DC converter saves lots of board space. The reinforced capacitive isolation barrier is certified according to VDE V 0884-11 and UL1577 and supports a working voltage of up to 1.2 kVRMS. The isolation barrier separates parts of the system that operate on different common-mode voltage levels and protects the low-voltage side from hazardous voltages and damage. Output is fully isolated from the input and optimized for high voltage interface. The project provides differential output for easy interface with ADC. Operating Power supply 5V DC.

Analog Output

The analog outputs are fully differential signals centered at a common-mode output voltage of 1.44 V. The outputs are available on the header connector CN2 and swing from 0.5 V to 2.5 V when a negative to positive full-scale linear input signal is applied to the input. OUTN swings from 2.5 V to 0.5 V when a negative to positive full-scale linear input signal is applied to the input.

Various Current Range Can be Achieved with Different Shunt Resistors

• For +/-2A Measurement Shunt Resistor R5 = 0.1E Ohms 2W-3W = Differential Output Range of –2.05V to 2.05V
• For +/-10A Measurement Shunt Resistor R5 = 0.025 Ohms 3W-5W = Differential Output Range of –2.05V to 2.05V
• For +/-50A Measurement Shunt Resistor R5 = 0.005 Ohms 12.5W External Shunt = Differential Output Range of –2.05V to 2.05V

Use the Following Formulas to Calculate the Shunt Resistor

• Vout = I_in x R_shunt x 8.2V
• R_shunt=V_shunt/I_inMax=250mV/2A=100 mOhms

Features

• Operating Supply 5V (Range 3.3V to 5V)
• Single Supply Operation
• Output Fully Isolated from Input
• Good for High Voltage Current Sense Applications
• Can Be used for AC or DC Current Sense
• Integrated Isolated DC/DC Converter (Chip)
• Current Measurement Range -2A to 2A
• Differential Output Range of –2.05V to 2.05V
• Output at Zero 1.44V
• Amplifier Gain 8.2V
• On-Board Power LED
• PCB Dimensions 57.94 x 19.69mm
• 2 x 2.5mm Mounting Holes

DIAG PIN

The open-drain DIAG pin can be monitored to confirm the device is operational and the output voltage is valid. The DIAG pin is actively held low until the high-side supply is in regulation and the device operates properly. During normal operation, the DIAG pin is in high-impedance (Hi-Z) state and is pulled high through an external pullup resistor. The DIAG pin is actively pulled low if:

• The low-side does not receive data from the high-side (for example, because of a loss of power on the high side). In this case, the amplifier outputs are driven to the VFAILSAFE value.
• The high-side DC/DC output voltage (DCDC_OUT) or the high-side LDO output voltage (HLDO_OUT) drop below their respective undervoltage detection thresholds (brown-out). In this case, the low-side may still receive data from the high-side but the data may not be valid. The amplifier outputs are driven to the VFAILSAFE value

Schematic

Parts List

Connections

Application Diagram

Simulation Results

Gerber View

Photos

Video

AMC3301 Datasheet

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