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Original question:

AMC0330S-Q1: REFIN voltage reference

AMC0330S: REFIN voltage range

Z. LI
Prodigy 80 points

Part Number: AMC0330S
Other Parts Discussed in Thread: AMC0311S

In thread https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1447069/amc0330s-q1-refin-voltage-reference Saleh said "The VREFIN pin should be ideally between 1.25V and VDD-1.25V. "

But in the datasheet its listed as 0-VDD2, there is even an example where REFIN is connected to GND in chapter 8.2.2.2.

So which one applies ?

 

  • +1
    TI__Expert 3921 points

    Hello, 

    there are two types of single ended output isolated amplifiers.

    a) Ratiometric (variable gain)

    b) Fixed gain

    They both have REFIN input pin but they work differently. 

    For the AMC0330S device, the REFIN pin can accept voltage as it is stated in the datasheet -> VREFIN = 0 to VDD2.

    However, this amplifier is bipolar input with +/-1V range. If you connect REFIN to ground, you can't sense the negative polarity on the input as the output will clip.

    This is the reason why Saleh suggested having a 1.25V up to VDD-1.25V as it allows full output swing in both polarities without the output clipping.

    If you need only the unipolar device, then AMC0311S is 0 to 2V input.

    I hope this helps.

    Best regards, Jiri