Two Channel Current Sensor for High Voltage Range

Rajkumar Sharma
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SKU: EL154082
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This board is built using a 2 x INA149 precision unity-gain difference amplifier with a very high input common-mode voltage range. The project can be used as a current sensor for high-voltage applications, INA149 provides a common-mode voltage range of +/-275V. The project operates with a wide supply range from +/-5V to +/-15V. The circuit measures current by sensing the voltage drop across a series of resistors R_S, R4, and R12. The application circuit shows the INA149 used to measure the supply currents of a device under test. The sense resistor imbalances the input resistor matching of the INA149, thus degrading its CMR. Also, the input impedance of the INA149 loads R_S, causes a gain error in the voltage-to-current conversion. Both of these errors can be easily corrected.

Note: The project can be used to measure current up to 2A, of DC Bus with +/-275V, this project has a few additional optional components R5, R6, C7, C8, C10 + R10, R13, C11, C13, C14, they can be used to overcome of CMR error. Refer to the datasheet of INA149 for more info. All these components are SMD size 0805.

Current Sense Resistors

The board provides dual options for current sense resistors. Users may use THT resistors up to 3W R3, R11, or SMD 2512 R4 and R12 Up to 3W. The default circuit measures current up to 2A. Choose the appropriate current sense resistor for a higher or lower current sense range.

Features

Power Supply +/-5V to +/-15V (Wide Supply Range: ±2.0 V to ±18 V)
Output 500mV/1A
Common-Mode Voltage Range: ±275 V
Minimum CMRR: 90 dB from –40°C to +125°C
DC Specifications: INA149
- Maximum Offset Voltage: 1100 µV
- Maximum Offset Voltage Drift: 15 µV/°C
- Maximum Gain Error: 0.02%
- Maximum Gain Error Drift: 10 ppm/°C
- Maximum Gain Nonlinearity: 0.001% FSR
AC Performance: INA149
- Bandwidth: 500 kHz
Input Protection: INA149
- Common-Mode: ±500 V
- Differential: ±500 V
PCB Dimensions 46.36 x 33.34 mm
4 x 3MM Mounting Holes

The INA149 is a precision unity-gain difference amplifier with a very high input common-mode voltage range. It is a single, monolithic device that consists of a precision op amp and an integrated thin-film resistor network. The INA149 can accurately measure small differential voltages in the presence of common-mode signals up to ±275 V. The INA149 inputs are protected from momentary common-mode or differential overloads of up to 500 V.

Applications

High-Voltage Current Sensing
Battery Cell Current or Voltage Monitoring
Power-Supply Current Monitoring
Motor Controls

Connections

CN1: Pin 1 = +5V to 15V DC, Pin 2 = GND, Pin 3 = -5V to 15V
CN2: Pin1 = Current Sense +I Channel A, Pin 2 Current Sense -I Channel A
CN3: Pin 1 REFB=1 CH-A (No Use), Pin 2 GND, Pin 3 = Channel A Output, Pin 4 = REFA-1 CH-A (No Use)
CN4: Pin1 = Current Sense +I Channel B, Pin 2 Current Sense -I Channel B
CN3: Pin 1 REFB=2 CH-B (No Use), Pin 2 GND, Pin 3 = Channel B Output, Pin 4 = REFA=2 CH-B (No Use)
D1: Power LED

Schematic

Parts List

NO.	QNTY.	REF.	DESC	MANUFACTURER	SUPPLIER	SUPPLIER PART NO
1	1	CN1	3 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5316-ND
2	2	CN2,CN4	2 PIN SCREW TERMINAL PITCH 5.08MM	PHOENIX	DIGIKEY	277-1247-ND
3	2	CN3,CN5	4 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5317-ND
4	2	C1,C3	10uF/25V CERAM IC SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
5	4	C2,C4,C5,C6	100nF/50V CERAMIC SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
6	10	R3,C7,C8,C9,C10,R11,C11,C12,C13,C14	DNP
7	1	D1	LED SMD SIZE 0805	OSRAM	DIGIKEY	475-1278-1-ND
8	1	R1	1K 5% SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
9	10	R2,R5,R6,R7,R8,R9,R10,R13,R14,R15	0E SMD DSIZE 0805	YAGEO/MURATA	DIGIKEY
10	2	R4,R12	0.5E/2W-3W 1% SMD SIZE 2512	VISHAY/DALE	DIGIKEY	541-10290-1-ND
11	2	U1,U2	INA149 SOIC8	TI	DIGIKEY	296-30028-1-ND