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SN74LVCH16T245: SN74LVCH16T245 bus hold circuit

Sai Loo
Expert 4390 points
Part Number: SN74LVCH16T245
Other Parts Discussed in Thread: DRV8824, , SN74LVC16T245

Hi Team,

My customer is using SN74LVCH16T245 between motor driver DRV8824 and MCU.

In their circuit, they use pull-up resistor (in our datasheet, it is mentioning that pull up or pull down resistor with the bus hold circuitry is not recommended) because their output-circuitry is open-drain circuit from DRV8824.

The problem they encounter is that when fault output signal from DRV8824 becomes low and then fault output is disabled, fault signal should be high voltage 5V, but sn74lvch16t245 will keep the voltage level stay 1.28V. Is this related to the bus-hold circuitry. Could you help to explain bus-hold circuitry? Why keep to be 1.28V ?

  • 0
    TI__Guru 56380 points
    hi sai loo ,

    app note regarding the bushold circuitry is here : www.ti.com/.../scla015.pdf

    what is the value of the pullup resistor ? There is a weak feedback internally in all the bushold circuits which keeps the last state. having pullup resistors will cause additional loading on the driver. The app note also talks about the calculation of the pullup resistors to be > 50kohm.
    the easiest way to verify would be to change the device to sn74LVC16T245 to verify if the issue is fixed.