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TPD2E001: Vcc Pin Usage

Kengo.Y
Guru 10385 points
Part Number: TPD2E001

Hi team,

Could you tell me about the leakage current for IO to VCC when VCC is no power?

According to the datasheet, IOpin is referenced to VCC.
When the VCC has no power supply and a signal is applied to the IOpin, a voltage can be seen at VCC.

Is there any way to prevent this?
As a system, the signal is input to the IO pin even if there is no VCC.

Sincerely.
Kengo.

  • 0
    TI__Expert 5660 points

    Hi Kengo,

    Thank you for your question. Our team is currently on holiday, we will have an update for you this coming Monday, November 30th. We appreciate your patience. 

    Best regards,
    Kate

  • 0
    TI__Expert 8471 points

    Hello Kengo,

    Thank you for your patience.

    If you look at section 8.2.2 of the datasheet, it explains that the Vcc pin can be used in two different ways. Please refer to the screenshot below.

    Basically, if a power supply is connected to the Vcc pin , it will act as a sort of biasing voltage and cause the signal to clamp to the power supply at Vcc + Vf. If a power supply is not connected to the Vcc pin, the diode will start conducting at around 10 V.  

    When leakage current was measured on this device, the IO voltage was swept from 0 V (GND) to whatever the voltage being applied to the Vcc pin was (probably 5.5 V), and the min and max leakages were recorded in the datasheet. 

    Now, for your use case, is it normal to see a voltage at the Vcc pin since that is the path the signal travels from the IO pin (should be Vio - Vf). However, if the Vcc pin is connected to a supply that has a lower voltage than the IO pin, it is possible that the current will leak into the supply. If you want to prevent this, I would recommend one of these three options. 

    1. Disconnect the Vcc pin if your system can handle the 10 V swing. 
    2. Make sure the Vcc DC voltage never drops below the IO DC voltage.
    3. Choose a different part that does not have a Vcc pin. (Page 23 of this guide explains the advantages of not using a Vcc pin)

    Please let me know if you need anymore clarification on this. If this solved your problem, please click the "Resolved" button.

    Regards,

    Matt Smith