This level shifter offering bidirectional voltage translation of up to four independent signals, converting 3.3V up to 5V or 5V down to 3.3V. The logic high levels on each side of the shifter are achieved by 10 kΩ pull-up resistors to their respective supplies; these provide quick enough rise times to allow decent conversion of fast mode (400 kHz) I²C signals or other similarly fast digital interfaces (e.g. SPI or asynchronous TTL serial). External pull-ups can be added to speed up the rise time further at the expense of higher current draw. See the schematic diagram below for more information.