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SN74GTL16612: GTL/GTLP/BTL

Tano Alejandre
Prodigy 20 points
Part Number: SN74GTL16612
Other Parts Discussed in Thread: SN74FB1653, SN74FB1650, SN74GTL2014

Does SN74GTL16612 support BTL application? Is there documentation for this application.

  • 0
    TI__Guru* 96947 points
    Hello Tano,
    No the SN74GTL16612 is specified for GTL applications.

    The devices we have that support BTL are:
    SN74FB1653
    SN74FB2031
    SN74FB2040
    SN74FB2033A
    SN74FB1650
  • 0 in reply to Emrys Maier
    TI__Genius 11455 points
    Hi Emrys,
    I am interested in the question as well and have a follow-up question. We have an old App Note that discusses using GTLP devices in BTL applications by shifting the VTT and VREF voltages of the GTLP transceiver. Can this also be done for the GTL/GTL+ devices, or is there something different about the GTL/+ devices that won't support this technique?
  • 0 in reply to Mark Guastaferro
    TI__Guru* 96947 points

    Hi Mark,

    We chatted via internal email, but I wanted to also post the resolution to E2E in case anyone else needs the information.

    I think good parts to compare will be:

    SN74GTL2014 (4 bit LVTTL-GTL transceiver)

    SN74FB2040 (8 bit TTL-BTL transceiver)

    SN74GTLPH32945 (32 bit LVTTL-GTLP transceiver)

    I grabbed a few specs to compare:

    Spec BTL GTL GTLP
    I_OL (B port, max) 100 mA 50 mA 50 mA
    I_OL (B port, absolute max) 200 mA 80 mA 100 mA
    V_OL (B port, max) 1.15V @ 100mA 9,4V @ 40mA 0.55V @ 50mA
    V_IL (B port, max) 1.47 V Vref - 50mV Vref - 50mV
    V_IH (B port, min) 1.62 V Vref + 50mV Vref + 50mV
    V_ref (range) N/A 0.5V - Vcc/2 0.74V - 1.1V*

    * Although not explicitly stated, the Vref for the GTLP device can be lower or higher than these values - these are the recommended values for GTL or GTLP operation. I would recommend staying within the 0.5V - Vcc/2 range.

    Looking at the above values, I see a few things.

    First, the GTL part can be setup to receive the correct voltage levels for BTL operation just by setting Vref = 1.52V, as can the GTLP device.

    The biggest difference between these is in their rated output drive current.  The BTL device is rated to directly drive a 50 ohm load at up to 100mA, and even supporting up to 200mA when required.  The GTL and GTLP devices have much lower maximum current ratings.

    In order to drive a BTL line, the current would have to be slightly reduced by adding a series damping resistor to each output on a GTL or GTLP device, or the load resistance value would have to be slightly increased.