The NCT5917W is a CMOS integrated circuit that provides bidirectional level shifting between higher voltage (2.7 V to 5.5 V) and low voltage (down to 0.9 V) .  Bus frequencies up to 400KHz are supported. While retaining all the operating modes and features of the I²C-bus system during the level shifts, it also permits extension of the I²C-bus by providing bidirectional buffering for both the data (SDA) and the clock (SCL) lines, thus enabling two buses of 400pF. The SDA and SCL pins are over voltage 5V tolerant and are high-impedance when the NCT5917W is unpowered.