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# INA190: INA190

Part Number: INA190
Other Parts Discussed in Thread: INA237, INA238, INA228, INA229, TLV700, INA186, ADS1100, INA191

Dear Experts,

Can you suggest some hardware or electronics for voltage source V1 ,V2 and DAS in the below circuit to work.

I have attached the circuit and also pasted it here.PIM_Fixture_DEC_04.pptx

Please find below and attached, the proposed circuit to measure the RESISTANCE of the SAMPLE, which is a metal strip (referred below as “SAMPLE UNDER TEST”).

1. We have estimated that the PIM (SAMPLE UNDER TEST) sample has a resistance in the range of a few 100 micro ohms (< 1 milli ohm).
2. Hence, we intend to use the PIM sample itself as a shunt resistor.
3. In the below test fixture, following are the settings:
1. We use a Variable power source that can be set to deliver a constant current (10A in this case) at a low voltage (1V)
2. We use another voltage source to provide 5V or 10V to the INA190A5 current sense amplifier. INA190A5 (Gain = 500) is used to measure the current flowing through the PIM sample.
3. The voltage output from the INA 190 A5 is measured by the Data Acquisition System (DAS).
4. Using the measured voltage  from INA190 A5, we determine the resistance of the PIM sample, as follows
5. Since we expect the PIM resistance to be less than 1 milli ohm, we expect the Vout to be not greater than 5V.

i.      Set current = Iset = 10A

ii.      Gain of the current sense amplifier (INA186A5) = Gain = 500

iii.      Measured voltage at OUT pin of INA186A5 = Vout

iv.      Resistance of the PIM sample = R

v.      Hence R = (Vout) / (Gain x Iset) = (Vout) / (5000)

• Hey Amit,

My apology for the delay. Thanks for posting to the forum.

In general, you will want V1 to be a very stable source as this will be the most important hardware because you need to know the exact value of the current. There are a couple routes to take with V1. You could just use a normal DC Voltage supply, but since these are voltage-controlled sources, you will need some load resistance to set the current to ~1A; however, this will require a high-power resistor (10Ω/10W). Even if you have this resistor you will have some load variation as the temperature of the resistor will rise, change its resistance, and this will change the Iset current. You could use another 1mΩ shunt resistor along with another INA186A5 current sense amplifier to measure the real-time current during the testing.

Another route to take with V1 is to use an electronic load instrument. In this case V1 would be a current source and you would simply set the load current to 10A. The issue is that these instruments can be costly and the accuracy of the resistor measurement will be dependent upon the accuracy of the current source's specification in output current error.

V2 just needs to be a basic, 5V, low PSRR LDO.

The DAS just needs to be >12-bit delta-sigma ADC. The throughput (sampling frequency) does not need to be high because you are making slow, DC measurements.

Another option is to use one of the INA229/INA228/INA237/INA238, which are very accurate monitors that include the ADC internally.

Hope this helps.

Sincerely,

Peter

• Hi Peter,

Thank you very much for answering my query.

To be more specific can you please guide us the product no for recommended low PSRR LDO, can it be TLV700(TI Product) along with a variable DC voltage source(Please check the attachment)

Can we use the 2 voltage source (the attached one) for both V1 and V2.

If not can you recommend some product details for V1 & V2 voltage source.

For DAS , can we use ADC12EU050(TI Product).If not any recommendation,

Thanks

Amit283_pdf.pdf

• Hey Amit,

You could use the TLV700 to power the INA186; however, it max output voltage variant is 3.6V, which is a valid supply voltage for INA186, but I would recommend using a 5V supply (Vs) for INA186 to maximize dynamic range and thus maximize resolution in your measurement. In the link I sent, I tried narrowing down the selection of the LDOs by setting the Vout voltage to something in between 1.8V and 5.5V, but I am not sure it worked. Here is another parametric search selection where I narrowed down the LDO options with Vout and setting the minimum PSRR at 100kHz to 40 dB minimum. It looks like the TPS7B83-Q1 could be a very nice option, but there are plenty of good options. As long as the INA186 is receiving a stable 5V at Vs pin with the recommended 0.1uF decoupling capacitance, the device will operate perfectly fine.

For the ADC, I will send a more narrowed selection from our parametric search. I would not recommend the ADC12EU050 as this is only 12-bit with an architecture that is not just purely a delta-sigma. Given you only need to precision measurements and not very fast measurements, I highly recommend a >12-bit delta-sigma ADC that can take in a 0-5V single-ended input. The ADS1100 looks like a great option.

As for the DC voltage supply (V1) you show this seems like it could work; however, I cannot decipher its accuracy specification of "+/-3D". I do not know what this means so I would double-check this specification and make sure that it meets your system's overall accuracy requirement for the measurement of the shunt's resistance. V1's resolution is 10mA, so if "3D" means "3 digits", then the worst-case error at 1A output is 100*30mA/1A = +/- 3%. This could be an incorrect interpretation of the manufacturer's spec, but it does show that even with the current display for V1, you still may need a more accurate measurement of the current using a separate circuit as I mentioned in the previous post.

One other thing is I would consider using the INA190 or INA191 instead of the INA186 as these are very similar to the INA186, but have much better accuracy (smaller offset and gain error) and you will want this accuracy in order to make these precision measurements.

Sincerely,

Peter