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ADS1248 and DDC118, output driver strength

Vitali Lach
Expert 1130 points
Other Parts Discussed in Thread: SN74LVC8T245, SN74LVC07A, TXB0108, SN74LVC16T245, TXS0108E

Hello,

It's a very nice forum here.

I intend to use leveshifter TXB0108YZPR with those both ADC's. (Translation down to 3,3V) This levelshifter has a bidirectional driver that does need 2mA current for a short time to change the direction initially. I dont know whether the digital outputs of those ADC's are able to drive this current. Could you please help me with some information?

Many thanks in advance.

Vitali Lach

  • 0
    TI__Guru** 113765 points

    Vitali,

    Thanks for the nice comment!  Generally what happens is as the output current increases the the VOL and VOH also change due to the loading.  This may not be a problem at room temperature, but can be a problem and extreme temperatures.  Depending on the input threshold levels of the devices connected, there may appear to be a glitch in the signal.

    I generally do not use bi-directional level shifters unless I need a bi-directional operation such as I2C communication.  I do not believe you need bi-directional devices.  On various EVMs we have used level shifting transceivers such as the SN74LVC8T245.  I also know that the DDC114EVM uses an open drain buffer for level shifting (SN74LVC07A.)  Both of these parts also come in packages with fewer logic devices in case you don't want to use an 8 device part.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Expert 1130 points

    Hello Bob,

     

    you are right, I dont need a bi-directional device.

    The reason why I want to use TXB0108 is because that device is extremely small.

    Due to the lack of place on our PCB we are struggling to place all components.

    SN74LVC8T245 has 8 Bits, I have 12 bits to translate, do you know similar device with 16 bits? That would be great.

     

    Best Regards

     

    Vitali

     

  • 0 in reply to Vitali Lach
    TI__Guru** 113765 points

    Vitali,

    The 16 bit transceiver is the SN74LVC16T245.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Expert 1130 points

    Hello Bob,

    thank you very much for your sugesstions. I see that we have only two direction control signals. In my application I've got 10 outputs und 2 Inputs. I found another little bidirectional device TXS0108E and dont know whether it will works with those ADC's or not, I guess I should ask that in another forum section?

    Best Regards

    V.Lach