2 Channel Ultra-Precise Current Sensor

Rajkumar Sharma
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SKU: EL143438
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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.

Gain: the board is populated with an OPA2290A1 chip that has a gain of 20V/V, the user may choose the following chips with higher gain. Project provides 0.2V/A , 2V @ 10Amp Load.

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

NO	QNTY	REF	DESC	MANUFACTURER	SUPPLIER	SUPPLIER PART NO
1	2	CN1,CN3	3 PIN SCREW TERMINAL PITCH 5.08MM	PHOENIX	DIGIKEY	277-1248-ND
2	1	CN2	4 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5317-ND
3	1	C1	100nF/50V CERAMIC SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
4	1	C2	10uF/25V CERAMIC SMD SIZE 1206	YAGEO/MURATA	DIGIKEY
5	2	C3,C4	DNP
6	1	D1	LED RED SMD SIZE 0805	OSRAM	DIGIKEY	475-1278-1-ND
7	1	R1	2.2K 5% SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
8	4	R2,R4,R5,R7	0E	YAGEO/MURATA	DIGIKEY
9	2	R3,R6	0.01E/3W 1% SMD SIZE 2512	BOURNS	DIGIKEY	CRA2512-FZ-R010ELFCT-ND
10	1	U1	INA2290A1	TI	DIGIKEY	296-INA2290A1IDGKRCT-ND