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TL16C754B: Iih and Iol when driven by SN74LVC244APW

Phaniendra Kundeti
Intellectual 260 points
Part Number: TL16C754B
Other Parts Discussed in Thread: SN74LVC244A

Hi,

TL16C754B is driven by SN74LVC244APW. Buffer datasheet electrical specifications have various test conditions for different Vcc and IOH & IOL and corresponding VOH & VOL. Now when this buffer is driving UART then what is the IIH & IIL of UART are required to check the logic compatibility. But this information is not given in the datasheet of UART.

Considering worst case VOH & VOL then serial controller is incompatible with Buffer. Kindly provide necessary insight into this.

Our supply is 3.3V

Buffer:

VOH -> 2.2(Min) worst case as per datasheet if VDD=3.0V(data not available for 3.3V) at -40to85 operating condition

VOL ->0.55(Max) worst case as per datasheet if VDD=3.0V(data not available for 3.3V) at -40to85 operating condition

UART:

VIH -> 0.7VCC (ie., 2.31 @ 3.3V ) (Min)

VOL-> 0.3VCC(ie.,0.99 @3.3V) (max)

Regards,

Phaniendra Kundeti.

  • 0
    TI__Guru 62920 points
    Hi Phaniendra,

    While we don't have detailed characterization data on this parameter, in general the logic inputs of the TL16C754B should sink very little current as they are designed with high-impedance buffered inputs. The SN74LVC244A device would be compatible as long as the output current were 12 mA or less, and in this case the current should be significantly less than that. (I would not expect it to be as high as even 1 mA.)

    Regards,
    Max
  • 0 in reply to Miguel Robertson
    Intellectual 260 points
    Hi Max,

    Can you give any data or maximum sink current of TL16C754B. May I know the reason why this info not available in TI datasheet. Theoretical compatibility has to be demonstrated to the customer.

    Regards,
    Phaniendra
  • 0 in reply to Phaniendra Kundeti
    TI__Guru 62920 points
    Phaniendra,

    I am not sure of a good reason for it not being documented initially other than being considered a relatively non-critical parameter due to the impedance being high enough to not restrict most applications. A very conservative estimate for an upper limit on the input current, though, would be 10 mA, which would allow for clear compatibility with this buffer device.

    Max