During operation, TXB0304 can work at both VCCA ≤ VCCB and VCCA ≥ VCCB . During power-up sequencing, any power supply can be ramped up first. Both the supplies are recommended to be powered down together. The TXB0304 has circuitry that disables all input/output ports when either VCC is switched off (VCCA/B = 0 V).