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XTR110 Extend Span

Ken Hashi
Intellectual 790 points
Other Parts Discussed in Thread: XTR110

Hello.

The customer wants to use it as VI converter of the output (0-40mA) for input (0-10V).
And the customer is going to use XTR110.
Expand SPAN by connecting resistance between 1 -16 pin pins in parallel with internal resistance R9 (datasheet Figure 1.), and do not have any problem?

It means whether there is possibility of destruction and the trouble in a customer wanting to know it.
The customer thinks that the problem of precision, the error is restrictive.

Actually, using internal R9 (50 Ω), connect external resistance (51 Ω) more between 16pin and 1pin, and do it to 25 Ω by composition resistance, and be that I double a span and use it.

Regards.

K-hashi.

  • 0
    TI__Guru 62055 points

    Hello K-hashi,


    The maximum current through the internal 50 Ohm resistor is 40mA. By placing an external 50 Ohm resistor in parallel with the internal 50 Ohm resistor the current through each resistor should be roughly 20mA and the internal resistor should not be damaged. Be aware that the gain accuracy of the XTR110 comes from the ratio matching of the internal 500 Ohm and 50 Ohm resistors and not either of their absolute values. That means that the resistors are just as likely to be 500/50Ohms as they are 400/40 or 600/60. Therefore, placing an external 50 Ohm resistor between pins 1 and 16 will not necessarily produce the 0-40mA output span you desire because the equivalent parallel resistance may not be 25 Ohms.

    A better way to increase the output current span to 0-40mA is to place an external 25Ohm resistor between pins 1 and 13 and do not connect pin 16 to anything. This is shown in both Figure 8 and 10 in the XTR110 datasheet. The Span and Offset adjustment circuits shown in Figure 8 may be useful to correct for any gain error in the final system.


    The basic circuit connections for this system are shown in the image below:

    XTR110_0-10_to_0-40mA.TSC

  • 0 in reply to Collin Wells
    Intellectual 790 points
    Hello Collin,

    Thank you for your answer and kind suggestion.
    We understand what we should think about.

    Best regards,
    K.Hashimoto.