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TXB0108: TXB0108 input current

switch
Genius 4100 points

Part Number: TXB0108
Other Parts Discussed in Thread: TXU0304

Hi Ti Team,

How to test the Level Shift IC input and output current? Can you give me the test method?

  • 0
    TI__Mastermind 47615 points

    Hey Switch,

    What exactly are you looking for? Are you looking for general methods to measure current in a circuit?

  • 0 in reply to Dylan Hubbard
    Genius 4100 points

    Hi Dylan,

    1. What current is represented by the green box (Continuous output current, 50mA) below? 

    2. The ICCB current in the red box below is 5uA. Does each port of B1~B8 mean 5uA? Or is the current of all ports B1~B8 add up to 5uA? Or is it the current of VCCB?

    3. In Test Condition in 6.5 Electrical Characteristics, the current value of IOH and IOL is 20uA, what current is this?

  • 0 in reply to switch
    Guru 324370 points

    1. The absolute maximum rating says that if you try to draw more than 50 mA, the device might get damaged. This does not happen during normal operation.

    2. ICC is the supply current, i.e., current that flows into VCC and out of GND. It is measured when the device is idle, without anything connected to the outputs.

    3. IOx is the drive strength of the TXB's outputs. And it is indeed 0.02 mA; if you try to draw more current, you will get a larger voltage drop that will make the signal unusable.

    The input current is up to 2 mA (see section 8.3.2 of the datasheet).

    The TXB is not a buffer, and should be used only when you actually have bidirectional signals. All your signals appear to be unidirectional; a better choice would be 2× TXU0304.

  • 0
    Prodigy 40 points

    Hi TI Team,

    This is Zoe from Zylux technology center Korea.

    We have a qeustion regarding item3 below. 

    We can see the output drive strength is 20uA in the datasheet, does it mean the current for each port of B1 to B8 is 20uA? Or the total current of B1 to B8 is 20uA?Please help clarify. Thanks. 

    Best regards,

    Zoe

  • 0 in reply to Zoe Jo
    Guru 324370 points

    This current is per port.

  • 0
    Prodigy 40 points

    Hi TI Team,

    One more question from our engineer. 

    We can see the input strength is 2mA in the datasheet, is it possible to increase the input strength to make the output strength up to 100uA per port?

  • 0 in reply to Zoe Jo
    Guru 324370 points

    The input and output buffers are separate circuits. The TXB's output strength cannot be increased; use another device like the TXU.

  • 0 in reply to Clemens Ladisch
    Prodigy 40 points

    If a current of 60uA continues to flow in one port, a voltage drop occurs, but is it usable or is there a possibility of component destruction? Is there an internal protection circuit?

  • 0 in reply to Zoe Jo
    Guru 324370 points

    The absolute maximum rating is 50 mA, so there will not be any damage.

    The input and output buffers on both side are always active. You have to ensure that the voltage stays above VIH or below VIL, and the only way to do that is to keep the current below 20 µA.