INA250-Q1: INA250A2 power source to +IN & VS pin can be same or not?

Hi Latha,

have you read section 9 of datasheet?

But with REF = 0V you will not be able to measure currents down to 0A or even negative currents. This will drive the output into saturation:

For this you will need to supply a small pseudoground at the REF pin:

latha_ina250_1.TSC

Kai

Oppss... Kai, I referred the Forum comments and share the same image here. Could you please share me the clear schematics for my application. 24VDC/10A source passing through INA250A2. Need a ADC output with in 3.3VDC (micro supports only 3.3V) worst case 5V. In such case Vref voltage and how do I source that power if it is 2.5V? I need a reference design kit for better understanding

Is there any IC to power up the REF pin? Please share the PN of the same.

Hi Latha,

figure 41 of datasheet shows a suited method to provide a pseudoground to the REF pin.

If your µC (and ADC) is supplied with 3.3V, you should supply the INA250 with 3.3V as well. Otherwise you need a protection circuit at the input of ADC when using a higher supply voltage for the INA250.

And how the final circuit could look like depends on your ADC, which I don't know.

Kai

Hello Latha,

Kai is correct in his statements. If you are trying to interface with an ADC it would be useful to match the supplies (INA and ADC) as Kai mentioned. I also see you are using a TPS62147 which is a step down converter with Vin max of 17V and Vout max of 12V this will not work with your need of 36V Vin and 24V Vout. Also in the case of measuring the inductor current in a switching power supply when in CCM or DCM the current will go down to zero and also below zero meaning you will need a reference on the REF pin to measure this current. Buffering the REF as in figure 41 (top INA) will work.

Regards,

Cas

Can we have a call to clarify more questions which I have. Let me know your convenient time or please set up a call. IST 8AM TO 9PM works well to me.

Hi Kai, Please take this request on priority. What is the preferred op-amp for the below application?

Please respond to the above request as earliest

I was looking for TI Part. Any suggestion on that? 

The TLV6001 could be used with a pseudoground >=300mV.

Or the LMV611 with a pseudoground >=200mV.

But let's see what Castrense is recommending.

Kai

 Castrense Nigrelli  , Any recommendation on the above ask by Kai??? 

Latha,

why is it so difficult to find a suited OPAmp by yourself?

Kai

Hello All,

Sorry for the late reply but I was out of the office.

Latha,

Since the INA250 is very precise I would go with a precision op Amp with a rail to rail input and output as Kai mentioned. You can use the parametric search on the TI website to narrow down the results and choose the best package and price op Amp.

Here is a link to the parametric search for precision op amps: https://www.ti.com/amplifier-circuit/op-amps/precision/products.html#p480=1;1&~p78=In;Out&p1498=Catalog&p1261max=3.3;180&p1261min=1.6;3.3

As Kai mentioned there are also general purpose op Amps which are less expensive that will work. The TLV6001 mentioned by Kai can work and is less expensive than the precision op Amps. A similar parametric search can be done with the general op Amps portfolio to get the best op Amp for you.

In the email I wrote to you I was trying to outline the equations to follow. You should first identify the current range you need then set the Vref. Once you set the Vref the resistors can be chosen with the voltage divider equation. Set one resistor to ~10's of kohms and solve for the other.

Regards,

Cas