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Output of INA139-Q1

Masami Michino
Genius 5070 points
Other Parts Discussed in Thread: INA139-Q1, INA169, TINA-TI


Dear, All

Customers are using the INA139-Q1.
They are to insert a diode between GND and INA139-Q1's GND for protection reverse connection.
Schematic diagram is as follows.

Because of this configuration, output voltage is generated, when the current of the current sense resistor is 0A.
They want to calculate the voltage to be generated in the output.
I'm happy if you know the equation of this voltage generated.
In addition, I want you to tell me if you know the impact of changes in temperature.
For example, output voltage is increased.

This condition is,
- V + -> 5V
- Rl -> 47kΩ
In addition, Vf of the diode is 0.45V when INA139-Q1 Operating.

Thanks, Masami M.

  • 0
    TI__Genius 15760 points
    Hi Masami,

    With this configuration you are limiting the current of the resistor because OUT can not go below the GND pin voltage. The voltage at the GND pin will change depending of the current through D1 and the temperature of the diode.

    I believe a better way to accomplish your goal is to connect the lower end of Rl to pin 4. Your output is not referenced to pin 4 of the INA169 and not GND. This will compensate for any changes in current through D1. Make sure that V+ to GND still meet operating voltage range.

    Regards,
  • 0 in reply to Mayrim Verdejo
    Genius 5070 points


    Hi, Mayrim-san

    Thank you for your reply.
    I'm sorry for my late reply.


    Dear, All

    I simulated it in TINA-TI.
    However, I do not unite an actual value.
    I added the voltage that I measured in substitution for a diode by the simulation.
    Diode Vf of the actual value
    0.49V
    Sense resistance
    2m Ω

    Measurement value:
    Current INA139-OUT
    0.1A 62.32mV
    0.5A 75.44mV
    1A 107.97mV
    2A 193.51mV
    3A 283.79mV
    5A 464.23mV

    As a result of having simulated it in TINA-TI
    Current INA139-OUT
    0.1A 448.78mV
    0.5A 449.05mV
    1A 449.44mV
    2A 450.41mV
    3A 451.83mV
    5A 479.87mV

    The customer wants to check how INA139-OUT changes by a change of diode Vf.
    The circuitry improves for the first question.
    I want you to advise a method of the simulation.

    Thanks, Masami M.