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TXS0101 External Pull-down

Ingmar van Klink
Prodigy 70 points
Other Parts Discussed in Thread: TXS0101

Hello,

I've got an application where on I/O connection of the TXS0101 requires a bootstrap setting of below 0.25V. Taking into account the 10kOhm pull-up internally (to 3v3) in the TXS0101, I have to use a pull-down resistor of approx. 800 Ohm. On the other side of the translator I've got a driver that is capable of sourcing 5mA. Summarized: Vccb = 3v3, I/O B = pulled down with 800Ohm. Vcca = 1.8V, I/O A is driven to 1.8V with a 5mA capable driver. 

Is the TXS0101 capable of driving the 800Ohm resistor with enough current to get a voltage level of >2.5V?

Are there some formulas available for calculating min/max pull-up/down values?

Thanks,

Ingmar

  • 0
    TI__Expert 6430 points

    Hi,

    If VCCB=3.3V and 800ohm resistor is connected between B port and ground, the B port voltage value will equal to VCCB*800/(10K+800) when logic high is transferred. Thus, B port will be low logic with 800ohm pull-down resister when logic high is transferred from A port.

    Thanks

  • 0 in reply to Wei Lang
    Prodigy 70 points

    Hi,

    Thanks for the reply. When looking into the datasheet of the device, in the Absolute Max Ratings, a maximum output current of port A and B is given, 50mA. My driver on input A is sourcing with 5mA. Doesn't this current flow through the  device to port B? In that case, does a part of the current flow back into VCCB via the 10k? Or is there a protection diode inside the device? If that would be the case, the 5mA could flow into the 800R resistor, resulting in a positive voltage (clamped by the diode then).

    Thanks,

    Ingmar

  • 0 in reply to Ingmar van Klink
    TI__Expert 6430 points

    Hi,

    '+/-50 mA' is maximum value which measured at stress testing. The source current on port A will not flow to Port B. The input drive current just has effect on input port.

    Thanks