2 Channel Ultra-Precise Current Sensor

The project described here is a two-channel ultra-precise, current-sense amplifier that can measure voltage drops across shunt resistors over a wide common-mode range from 2.7 V to 120 V. The INA2290A1 chip is the heart of the project. The ultra-precise current measurement accuracy is achieved thanks to the combination of an ultra-low offset voltage of ±12 µV (maximum), a small gain error of ±0.1% (maximum), and a high DC CMRR of 160 dB (typical). The circuit is not only designed for DC measurement but also for high-speed applications (such as fast overcurrent protection, for example) with a high bandwidth of 1.1 MHz (at a gain of 20 V/V) and an 85dB AC CMRR (at 50 kHz). The project achieves ultra-precise current measurement by sensing the voltage drop across resistors R3 and R6.

The circuit operates from a single 2.7V to 20V supply with the single channel device only drawing 370µA + LED supply current per channel (typical). The devices are available with five gain options: 20 V/V, 50 V/V, 100 V/V, 200 V/V, and 500 V/V. The low offset of the zero-drift architecture enables current sensing with low ohmic shunts as specified over the extended operating temperature range (−40°C to +125°C). Screw terminals are provided to connect the load, header connector is provided to power the circuit, and analog voltage output.

Input Filter:  Input filtering components   R2, R4, R5, R7, C3, and C4 are optional. Please refer to the datasheet of the chip for guidelines on input filter components. All resistors are SMD size 0805, capacitor ceramic SMD size 0805.

• INA2290A1 devices: 20 V/V
• INA2290A2 devices: 50 V/V
• INA2290A3 devices: 100 V/V
• INA2290A4 devices: 200 V/V
• INA2290A5 devices: 500 V/V

Features

• Power Supply 2.7V to 20V DC
• Output 0.2V/A (2V @ 10Amps)
• Wide common-mode voltage: Operational voltage: 2.7 V to 120 V
• Survival voltage: −20 V to +122 V
• Excellent CMRR: 160-dB DC. 85-dB AC at 50 kHz
• Gain 20V/V
• Accuracy: Gain error: ±0.1% (maximum), Gain drift: ±5 ppm/°C (maximum),
• Offset voltage: ±12 µV (maximum),
• Offset drift: ±0.2 µV/°C (maximum)
• High bandwidth: 1.1 MHz (C_LOAD = 5 pF, V_SENSE = 200 mV)
• Slew rate: 2 V/µs
• Quiescent current: 370 µA (per channel)
• 2 x 3mm Mounting Holes
• PCB Dimensions 31.43 x 29.21 mm

Connections

• CN1: Pin 1 = Load-1 DC Input, Pin 2 = GND, Pin 3 = +Load-1
• CN3: Pin 1 = Load-2 DC Input, Pin 2 = GND, Pin 3 = +Load-2
• CN2: Pin 1 = VCC 2.7V to 20V, Pin 2 = Output 1, Pin 3 = Output 2, Pin 4 = GND
• D1 Power LED
• Current Sense Resistor R3 and R6

Schematic

Parts List

Connections

Gerber View

Photos

Video

INA2290 Datasheet

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