Hello,
I am planning to use the INA228 to measure the current of LEDs. The maximum sense current in my application is 50mA. Common mode voltage will be 5V.
I would like to be able to monitor 50uA steps. Would this be possible by using a 3 Ohms shunt resistor?
Also does the supply voltage need to be very stable? Would l be able to supply 5V from a USB 2.0 ?
Thank you.
Hi Kostas,
Yes, a 3Ohm resistor should work fine for your application. Keep in mind that at a 50mA max current there will be a 0.15V drop across your shunt resistor, and if this is acceptable for your application.
The device itself has good Power Supply Rejection Ratio (PSRR), reference the electrical characteristics portion of the data sheet for power supply vs offset details.
Section 8.1 of data sheet shows how to set the calibration registers to achieve your desired Current LSB size (step size).
Yes, a standard chip SMD resistor can be used. Make sure the power rating of the resistor is within your application needs (shouldn't be a concern since only 7.5mW max dissipated for your case) and select a low enough percentage tolerance (at least 1%).
Use Kelvin connections from your shunt resistor to the device to ensure minimal error is introduced as recommended in section 10 of the INA228 datasheet.
Best Regards,
Angel
