• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 19 subscribers
  • Views 2170 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TXS0108E: Can I use this device for level translating active low RST#

Shanu V
Prodigy 130 points
Part Number: TXS0108E
Other Parts Discussed in Thread: TXB0108, SN74AVC8T245

1) In my design, in the initial condition, there should be a minimum delay of 300uS between VCC HIGH and rising edge of RST#.

Can I use TXS0108e for level shifting 1.8V RESET# to 3.3V by adding a 51k pull down resistor at the output side?

There are three devices(2xNOR flash and 1xoneNAND) to which RST# is given. Will this work as expected? Should I use TXB0108 instead of TXS01008?

2) Also, I am using TXB0108 for level shifting 1.8V ADDRESS and DATA to 3.3V level. Will this be able to drive all the three devices?

  • 0
    TI__Guru* 96591 points
    Hi Shanu,

    I have notified the appropriate applications engineer who should be back with you soon.
  • 0 in reply to Emrys Maier
    TI__Guru 55960 points
    Hi Shanu ,

    what is the purpose of 51k pulldown here ? The TXS has internal pullup resistor which enables up-translation . The low level , however , at the output will be very close to the low level at the input port. It doesn't require a pulldown resistor.
    The TXB has weak drive through 4K internal buffer, it may not be able to fanout into 3 devices. Is it possible to consider direction controlled translation instead ?
  • 0 in reply to ShreyasRao
    Prodigy 130 points

    Hi Shreyas,

    Thanks for the reply.

    What will be the output voltage of B1 port of TXS0108/TXB0108 if there is no input signal at A1 with both Vcca and Vccb enabled?

    What I understood was, both sides of TXS0108 will be high by default.

    I want to have a low value for RST# until the FPGA drives it high. 51k resistor was added by mistake, you can ignore that.

    Please suggest an option for this.

    Is there any push-pull device without direction control as replacement for TXB? If not, please suggest an alternate one with direction control.

  • 0 in reply to Shanu V
    TI__Guru 55960 points
    TXS default output will stay high because of the internal pull up resistor. For TXB, since they are active CMOS inputs , floating the inputs is not recommended. forcing input pins low to keep outputs low is advised.
    consider using direction controlled translator SN74AVC8T245 / 4T245. Again , the inputs cannot be floated and must be held at gnd.