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LMC6482: output swing test condition

Rory Wu
Intellectual 1050 points
Part Number: LMC6482

Hi team,

My customer used LMC6482 and was confused about output swing test condition, can you help share how to understand RL=2kohm to V+/2. We can understand 2kohm, but hard to get the meaning of V+/2. thanks.

BR,

Rory

  • 0
    TI__Guru 60610 points

    A default condition of Vcm = Vo = V+/2 means the input and output are in the middle between supplies; in case of 5V single supply this means Vcm=Vo=2.5V

    In case of output swing specification, RL = 2k to V+/2 means that the load resistor is connected between the output and mid-supply (2.5V). Since the swing to the rail is a function of the output current, this implies that the typical 100mV swing to the rails occurs under Iout = (4.9V-2.5V)/2k or (0.1V-2.5V)/2k = +/-1.2mA load.

  • 0 in reply to Marek Lis
    TI__Intellectual 795 points

    Hi Rory, 


    Let me show pictorially what Marek was explaining above.The data sheet specifies the output voltage range for different combinations of supply voltage and load resistor values. In each case, the load resistor is tied to the output in series with a V+/2 voltage source. If we take the first combination of conditions, 5V supply and a load resistance of 2 kOhm, we have a circuit equivalent to below – a 2 kOhm resistor is set in series with V+/2 = 2.5V. 

    Please let me know if this makes sense, and if you have any further questions. 

    Regards,
    Vladimir