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INA333: REF pin driver circuit

Parth Dholakiya
Expert 1245 points
Part Number: INA333
Other Parts Discussed in Thread: OPA333, REF3030, , OPA313, OPA314, INA326

Hi, I want to your help to design reference drive circuit for the ina333. The INA333 in my circuit is powered from ref3030 i.e 3V  and i want to give 500 mV to the REF pin of the ina333. The most commonly use opa333 is very very costly for our product budget. Can you suggest a cost effective solution for this?

The driver circuitry cost can be more around 0.1 to 0.2 USD.

 Thanks in advance!

  • 0
    TI__Guru 63510 points

    Vidula,

    Since you use a lower precision, 0.2% initial accuracy reference voltage, REF3030, there is no point on using high precision, more costly op amp for driving REF pin of INA333.  Therefore, the cost effective solution would involve using OPA314 or OPA313 as shown below. 

     

    You could also consider using INA326 for your solution, which unlike INA333 would give you rail-to-rail input common-mode voltage range.INA333 Vidula circuit.TSC

  • 0 in reply to Marek Lis
    Expert 1245 points

    Thanks for your suggestion. I will check with opa314 and opa313. INA326 is costlier than ina333 so we might not use that.

    Query:

    1) We are using ina333 for load cell output amplification.Load cell is powered from same ref3030 so at input of the ina333 the voltage is Vin+= 1.489 V and Vin= 1.489 V. Is it a proper setting or i need to change something. if you want to refer schematic then please let me know i will send you in private i cant share it on forum.

  • 0 in reply to Parth Dholakiya
    TI__Guru 63510 points

    Vidula,

    The circuit should work just fine and for the input common-mode voltage of 1.489V should result in the maximum output voltage range of 50mV<Vout<2.95V - see below.   I have assumed below a gain of 100 but if your gain is different, the maximum input differential voltage, (Vin+)-(Vin-), will have to be adjusted to reflect the actual gain.

  • 0 in reply to Marek Lis
    Expert 1245 points

    Gain resistor value is 220E so the gain is 455.

  • 0 in reply to Parth Dholakiya
    TI__Guru 63510 points

    Vidula,

    The range of the valid input differential voltage for your specific application is shown below.  It does not include the adjustment for the INA333 max Vos of around +/-25uV.

  • 0 in reply to Marek Lis
    Prodigy 10 points
    Hello,
    I found this topic while I was looking for additional information about using an INA333 in single-supply-operation. In the example in the datasheet the device is powered by a 3V power-supply and the REF-input should be supplied with 1.5V (= 3V / 2), but it doesn´t say how this can be realized.

    Now I found your topic and you want to supply the device through a voltage reference, ref3030, and your REF-input will be supplied by a simple op-amp-circuit that will halve the output voltage of your reference-voltage (ref3030).
    I was thinking about using a standard voltage regulator (LDO) to supply the INA. And for the REF-input I was thinking about using a reference voltage such as the ref3030.

    Could you please loose some words about the background and the advantages (maybe disadvantages?) of using a reference voltage to supply the INA?

    Best regard from Germany,
    Jörg