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Voltage Level Translator (3.3V to 1.8V Bidirectional)

Other Parts Discussed in Thread: LSF0204, TXB0104, TXS0104E

Hi,

I need a voltage level translator for I2S lines from 3.3V to 1.8V and vice a versa.Could you please

suggest a TI IC for the same.

Regards

Hari

  • Hi Hari,

    The LSF0204 will be a good fit for this application. The link below will take you to our Logic Minute videos which will provide great information on these voltage translators.

  • Hi Dylan,
    Thank you very much.Could you please tell me what and parameter we need to consider for selecting a voltage level translator.
    Let us say my i/p signal which needs to be translated has a frequency of 25Mhz
    Regards
    Hari
  • Hi Hari,
    The considerations for choosing a level translator are rather lengthy. To try to summarize quickly:

    Number and value of available supply rails & their limitations on current/voltage
    Board space limitations
    Power limitations
    Voltage/Current drive of transmitter - and driver type (open-drain vs push-pull)
    Leakage & capacitance (impedance) of receiver
    Parasitic capacitance from board/connectors/other devices on the line
    Geometry of transmission lines (sometimes can become an issue)

    -----

    All that being said, if you need to translate 4 channels (or less) bidirectionally from 3.3V to 1.8V (ie the signal can go one way or the other without any notice), then there are only really three choices:

    TXB0104 (best solution)
    TXS0104E (next best solution)
    LSF0204 (requires external pull-up resistors)
  • Hi Maier,

    Thank you very much for your time.
    May I know whether TXB0104 works fine at 25Mhz.

    Regards
    Hari
  • Hi Hari,
    As per the datasheet, section 6.10, the typical data rate when translating from 1.8V to 3.3V is 60 Mbps (30 MHz square wave).
  • Hi Maier,

    Thank you very much.Generally what are the timing parameters shoud I need to check before telling to anybody that this Level shifter can be used for that particular frequency.
    Regards
    Hari
  • Hi Hari,
    I'm not sure what you mean. The datasheet clearly lists a data rate, which is the number you need to know. Every spec in the datasheet has a purpose and is useful in one circumstance or another.

    Sections 6.11 to 6.15 of the datasheet list additional timing specs that you might need to know -- for example, the delay of the device is up to 4 ns for 3.3V to 5V translation. In many systems, this value is irrelevant, but some systems might have tight timing requirements and need to know it.

    Additionally, the TXB family of devices needs to be driven by a device with at least ( (Vcc/2) / 4000) mA of drive current (see figure 9 in the datasheet), and cannot drive DC loads of more than 20uA. The load should be kept below 70pF total capacitance (from all sources) to maintain stability and proper operation.
  • Hi Maier,

    Thank you very much. Actually what I asked is how to perform timing analysis of that IC wrt to my Clock.

    Regards
    Hari