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THS4031: PCN 20240314000.1 Clarification Question

Alex Segler
Expert 4561 points
Part Number: THS4031


Tool/software:

Regarding PCN 20240314000.1, the Differential Input Voltage has gone from +-4V to +-1.5V from Rev I to Rev L in the datasheet for part THS4031D.

 

Would you be able to help clarify the changes in voltages and if possible review the configuration below to see if the new changes would not impact it.

The inputs are supplied with 5V so the concern is with exceeding the new differential input voltage max rating.

  • 0
    TI__Genius 17695 points

    Hi Alex,

    That differential input voltage spec is the voltage difference directly at the two input pins. In a comparator type application pulling these inputs apart will lead to damage however in this type of application with negative feedback the inputs would ideally be following each other and the difference between them will be much less than 1.5 volts. With the 5V on both nodes in a difference amplifier configuration, we would not expect these two nodes to be pulled apart.

    Best Regards,

    Ignacio

  • 0 in reply to Ignacio Vazquez Lam1
    TI__Expert 4561 points

    Looking at the datasheet for HMC440QS16G DS the output voltage is 2Vpp. With the new differential input voltage in Rev L being +-1.5V, would that mean 3Vpp?

  • 0 in reply to Alex Segler
    TI__Genius 17695 points

    Hi Alex,

    The differential input voltage spec in amplifier datasheets refer to the voltage difference directly at the input pins. In any circuit with negative feedback, the goal of the amplifier is to keep these two nodes equal, creating a virtual short. This is not the same as the differential input signal of 2Vpp. These nodes at the input will adjust up and down as the input signal is changing however the output will adjust to force the input nodes to be equal. The spec is then referring to moments where the difference between the two nodes is above 1.5V, which we would not expect with this circuit because of the ideas mentioned.

    Best Regards,

    Ignacio