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INA1620: Voltage Coefficient Data for the precision resistors

Edward Cheung
Prodigy 10 points
Part Number: INA1620
Other Parts Discussed in Thread: RES11A-Q1, REF80,

Tool/software:

Dear TI Experts,

We have a project to build an input signal conditioner for a high precision ADC. Part of it is to divide the input by half while keeping the INL as low as possible. Do you have the voltage coefficient figures for the precision resistors (similar to what the datasheet of RES11A-Q1 provides)? Also, is this measured under constant die temperature or under constant ambient temperature? Thanks for your help.

Rgs,

Edward Cheung

  • 0
    TI__Mastermind 23650 points

    Hi Edward, 

    We don't have voltage coefficient data for the resistors on this device. The SiCr resistor metallurgy is the same as RES11 however. 

    • The volt co is dominated by the localized self heating which manifests as a temperature coefficient. In other words the volt co is impacted by the temp co. 
      • The voltage across the resistor causes current to go through it resulting in a temp rise and this temp rise gets multiplied by the temp co.
    • This temp co is not necessarily what is specified in the pds because that spec is referred to ambient temp. This is a localized temp co due to self heating.
    • The way the interdigitation works the self heating of the 1 network impacts the 2 network more than 3 and 4 networks and the self heating of the 4 network impacts the 3 network more than 1 and 2 networks. 
      • For a visual see below where I circled the 1 and 2 networks. 

    Best Regards, 
    Chris Featherstone

  • 0 in reply to Chris Featherstone
    Prodigy 10 points

    Hi Chris,

    Thank You. Is it correct that the output stage of Op-A is closest to the R2 network? Similarly, the output stage of Op-B is closest to the R3 network? If not, do you mind sharing with us the location of the output stage on the die for Op A and B?
    I know it's a strange question. We are not planning to use the op-amps for signal. Instead, we want to explore using the op-amps as heating element to ovenize the chip. As the signal voltage (which is DC) across the resistors various, we'll also adjust the PD of the op-amps to compensate. Unfortunately, there will be thermal gradient and there'll be some transient occur but that's the best we can do with an off-the-self component. In addition, we want to sense the die temperature via the quiescent current. By doing so, we hope to heat up the die and maintain a constant temp. The exact temp doesn't matter. Anything within 60-70 degrees C should be fine.

    Edward

  • 0 in reply to Edward Cheung
    TI__Mastermind 23650 points

    Hi Edward, 

    It is a neat idea. We have a device that was designed with the heating element in mind; the REF80. 

    https://www.ti.com/lit/ds/symlink/ref80.pdf?ts=1731538970333&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FREF80

    The INA1620 was designed for audio applications and not designed with this concept in mind so any information that could be of use isn't really known. It would be tricky because of thermal gradients on the die etc to give good answers. Unfortunately I wouldn't be able to share information on the location of the output as this is proprietary information. 

    Best Regards, 

    Chris Featherstone

  • 0 in reply to Chris Featherstone
    Prodigy 10 points

    Chris,

    Very beautiful device indeed. Looks like we can say goodbye to some TO-5 metal cans sticking on the boards :)