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OPA564-Q1: Application questions

Lanxi Li
Expert 6135 points
Part Number: OPA564-Q1
Other Parts Discussed in Thread: OPA564,

Hello team,

When customer tested the OPA564 power supply sequence, measured voltage rose from 0V to 3V, the rise time difference between Vsupply and VDIG was very small, basically the same. But when they tested the rise time of 0-4V, the difference between the two was about 0.5ms.

But as shown in the figure below, I only see the power supply range of VDIG in the data sheet, and I don’t know how much the voltage value of OPA564 determines VDIG is high level, so I would like to ask about the threshold value of OPA564’s VDIG determination as high level How many volts?

Thank you,

Lanxi

  • 0
    TI__Guru 56451 points

    Hi Lanxi, 

    Lanxi Li said:
    the threshold value of OPA564’s VDIG determination as high level How many volts?

    Vdig power on sequence in the OPA564/OPA564-Q1 is suggested in the schematic below, where no decoupling capacitors after Vdig node may be used. This will minimize the Vdig power on delay vs. the analog supply voltage.  

    For a single supply rail, where V- = GND = 0V, the minimum Vdig supply rail is 3.0Vdc and limited to 5.5Vdc. Upon the power on sequences > 3.0Vdc, the Vdigital block's power is already turned on, and Enable/Shutdown pin is already enabled after 2V, see the diagram below.    

    For the dual supply rails, assumed ±12Vdc, the Vdig pin is referenced to V- or V- = -12Vdc. So Vdigital rail  has to be > (-12V + 3V) = -9Vdc in order to activate the digital block (w.r.t. V- supply rail).  If the above condition is met, the Enable/Shutdown pin should be measured > (V-) + 2 = -12 + 2 = -10Vdc, and the power amplifier's output is enabled. 

    The power on sequence requirements are that the digital supply voltage (Vdig) be applied before or in sync with the analog supply voltage's power on sequence. The Vdig threshold's voltage shall be (V-) + 3.0Vdc, where the OPA564/OPA564-Q1's power on sequence requirements are met. 

    If you have additional questions, please let us know. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    TI__Guru 56451 points

    Hi Lanxi, 

    I am going to close this inquiry. 

    If you have additional questions, please email me. 

    Best,

    Raymond