Tool/software:
Hi，
My customer is INA210-Q1 and have several questions to ask.
Under normal circumstances, the current flowing through the shunt resistor of our product is about 65A~75A, and the i-peak will reach 200A.
1. What is the appropriate value for the shunt resistor used with INA210-Q1?
2. What is the expected current sampling accuracy of INA210-Q1?
3. If the maximum current to be sampled is 200A, can a current of 100mA be sampled?
BR,
Zach
Hi Mallika,
1. you can refer to block diagram below.
2. What is the voltage flowing through the product?
Usually it is 12V, and the customer requires that 5~18 can work
3. Which gain do you intended to use?
I am not sure yet, and I would like to hear your suggestions. We want to use gate driver for current sampling, but the voltage resolution is only 500uV.
Assuming that the sampling resistor is 0.00005 ohm, the current resolution can only reach 10A. 0.00005 ohm (shunt resistor) * 10 A = 0.0005V = 0.5mV = 500 uV (resolution)
Question 1: If I want the current sampling resolution to reach 100mA within the range of 0~200A, and the current sampling error to be controlled within 10%, what are your design suggestions for INA210-Q1?
Question 2: If INA210-Q cannot sample the entire range of 0~200A, can INA210-Q and gate driver work together, one to sample the high current part and the other to sample the low current part?
4. What is the supply voltage?
The voltage for INA210-Q1 is 5V
5. What kind of resistor are you comfortable using? Surface Mount? Special resistor?
Currently, we prefer surface mount devices
BR,
Zach
Hi Zach,
1.
What is the appropriate value for the shunt resistor used with INA210-Q1?
There are multiple factors to consider when selecting a shunt, I'll walk you through an example below.
Given the max measured current is 200A, Vs=5V, Gain = 50V/V.
If the supply voltage is 5V, then the output is limited to 5V, so then Vshunt = Vout/Gain = 5/50 = 0.1V. Rshunt = Vshunt / Iload = 0.1/200 = 500uOhms.
The power on the shunt then is P = V*I = 0.1*200 = 20W. This is a large power dissipation, so resistors that can handle this power will be larger in size. You could mitigate this by using two shunts in parallel to split up the current and power.
I've used TI's error calculation tool to calculate the offset and gain error at different gains. As you can see, the total error is within 10% beyond 65A, but at 100mA, the error is too large. This is because our device's range can span a max of 2 to 3 decades and the range from 100mA to 200A is close to 4 decades (200, 20, 2, 0.2).
2.
If I want the current sampling resolution to reach 100mA within the range of 0~200A, and the current sampling error to be controlled within 10%, what are your design suggestions for INA210-Q1?
When you say sampling resolution, do you mean you want the minimum measured current to be 100mA or the precision of the measurement to be within 100mA?
Measuring 100mA isn't possible if your range goes up to 200A, but having a precision of 100mA is possible.
Best,
Mallika Senthil
