The PCA9674/74A is a drop-in upgrade for the PCF8574/74A providing higher Fast-mode Plus I2C-bus speeds (1 MHz versus 400 kHz) so that the output can support PWM dimming of LEDs, higher I2C-bus drive (30 mA versus 3 mA) so that many more devices can be on the bus without the need for bus buffers, higher total package sink capacity (200 mA versus 100 mA) that supports having all LEDs on at the same time and more device addresses (64 versus 8) are available to allow many more devices on the bus without address conflicts.