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OPA455: How to design E/D_com and E/D in single mode

Yuxi Liu(Tony)
Expert 3360 points
Part Number: OPA455


Tool/software:

Hi TIer

Could you tell me about OPA455 if single negative power supply, without the en function, how the E/D and E/D_COM pins should be connected more suitable.

Is it not com to have negative power, then the E/D is still suspended ?

  • 0
    TI__Guru* 77541 points

    Hi Tony,

    Yuxi Liu(Tony) said:
    Is it not com to have negative power, then the E/D is still suspended ?

    Here is the OPA455's E/D and E/D_COM specification.

    This means that E/D (enable & disable) is referenced to E/D_COM voltage reference, and E/D_COM is reference to V- supply, where E/D_COM can be configured within a range of voltage, see in the green box. Once E/D_COM is defined, E/D logic has to be <7V (absolute maximum) above the E/D_COM voltage reference, see Vsd requirements. 

    Here is the example of schematic. 

    Yuxi Liu(Tony) said:
    Could you tell me about OPA455 if single negative power supply, without the en function,

    If you use single negative supply rail, then V+ = GND and V- can be as slow as -150Vdc. 

    Assume the following condition is true, where V- = -100Vdc. then you can set E/D_COM anywhere between -100V to -100+6 = -94Vdc. You can select a E/D_COM voltage that is convenient per your design. 

    And E/D logic voltage status shall meet  the following requirements. 

    If you have additional questions, please let me know. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    TI__Expert 3360 points

    Hi Raymond

    Thank you for your reply.

    The customer's supply voltage will change range from 20V to 75V or -20V to -75V due to special applications. So, could you give some advice on how to connect E/D and E/D com, can I float pin?

  • 0 in reply to Yuxi Liu(Tony)
    TI__Guru* 77541 points

    Hi Tony, 

    Yuxi Liu(Tony) said:
    ould you give some advice on how to connect E/D and E/D com, can I float pin?

    E/D_COM can not be in floating state. It has to connected to a known reference voltage, depending on V- (基于V- or Vee 的电压值). E/D (enable/disable) logic is then based on E/D_COM voltage reference. 

    Yuxi Liu(Tony) said:
    from 20V to 75V or -20V to -75V

    Assume you have two different configurations:

    1. 20Vdc <= V+ <= 75Vdc and V- = GND (single supply rail)

    2. -20Vdc <= V- <= -75Vdc and V+ = GND (single supply rail). 

    If customer is using dual supply rails, then E/D_COM pin can tie to GND directly and it simplified the E/D logics. 

    If you have other questions, please let me know. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    TI__Expert 3360 points

    Hi Raymond

    My customer will use the following settings as shown in Figure CC_VNN is variable voltage from -20V to -75V, E/D com is connect to V- . In this setting , the customer is eager to know if the E/D pin can be floating?

  • 0 in reply to Yuxi Liu(Tony)
    TI__Guru* 77541 points

    Hi Tony, 

    Yuxi Liu(Tony) said:
    E/D com is connect to V- . In this setting , the customer is eager to know if the E/D pin can be floating?

    Under the configuration, you may float the E//D pin, since E/D_COM pin's reference is defined now. 

    If you have other questions, please let me know. 

    Best,

    Raymond