SCES727A June 2008 – December 2014 TXB0104-Q1
During operation, ensure that VCCA ≤ VCCB at all times. During power-up sequencing, VCCA ≥ VCCB does not damage the device, so any power supply can be ramped up first. The TXB0104 has circuitry that disables all output ports when either VCC is switched off (VCCA/B = 0 V). The output-enable (OE) input circuit is designed so that it is supplied by VCCA and when the (OE) input is low, all outputs are placed in the high-impedance state. To ensure the high-impedance state of the outputs during power up or power down, the OE input pin must be tied to GND through a pulldown resistor and must not be enabled until VCCA and VCCB are fully ramped and stable. The minimum value of the pulldown resistor to ground is determined by the current-sourcing capability of the driver.