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MSP430FR2355: Maximum Input Current Limit of OP(SAC)

UNA
Mastermind 7980 points

Part Number: MSP430FR2355
Other Parts Discussed in Thread: MSP430FR2311

Hi,

What is the maximum input current to the built-in Opamp(SAC) in MSP430?
Also, the MSP430FR2311 has a built-in TIA, what is the maximum input current for this?

Best Regards,
UNA

  • 0
    TI__Mastermind 40195 points

    Normally we assume OPA has Infinite input resistance. 

    What is the input current mean? The current input OPA or anything else? 

    Can you tell me your application？

  • 0 in reply to Eason Zhou
    Mastermind 7980 points


    Hi Eason Zhou,

    I want to know the maximum value of the input current. Because the following datasheet only shows the TYP value.
    I connect the input from the sensor directly to the SAC(OP) or TIA. The input current can be more than 12mA.


    Best Regards,
    UNA

  • 0 in reply to UNA
    TI__Mastermind 40195 points

    Quiescent current refers to the current consumed by the operational amplifier when its state is stable.

    It will add into the MSP430 power consumption.

    As you say you connect  the sensor directly to the SAC(OP) or TIA, can you show me you schematic and the code. 

  • 0 in reply to Eason Zhou
    Guru 43745 points

    You showed the answer, it is the input bias current he needs.

  • 0 in reply to Eason Zhou
    Mastermind 7980 points

    Hi Eason,

    My customer is considering a gas detector application, but the circuit configuration will be done in the future.

    What I want to know is how much current can be input to the SAC(OA) or TIA terminals.
    For example, For example, the absolute maximum ratings of the TLV910x are specified in the data sheet as follows.


    In the same way, is it correct to assume that the absolute ratings specified in "Diode current at any device pin" apply to MSP430?


    Best Regards,
    UNA

  • 0 in reply to UNA
    Guru 43745 points

    When the device is configured as an input, the only time you can get these currents is if the pin voltage is far enough above or below Vdd/ground to cause the diodes to conduct. In normal operation, the input is very high impedance.

    Note that if you actuallly get to these limits, for example if VDD is off, you can actually power the chip from the pin!

  • 0 in reply to Keith Barkley
    Mastermind 7980 points

    Hi,

    I'm looking forward to get some insight from TI on this maximum rating.

    Best Regards,
    UNA

  • 0 in reply to UNA
    TI__Mastermind 40195 points

    Hi,

    Here is what I find on TLV910x:

    You can see that the current means when the input signal is beyond supply rails, the current will go through ESD diode to GND or VCC, it is not in a right setup.

    As I know about gas sensor, if the output signal is current, it normally will use a resister to get a voltage. You can take this as a reference.

    Here is what you want:

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