Adding the device as an I2C slave minimises integration effort and enables engineers to implement extra functions without specifying a more expensive microcontroller having a higher pin-count. Using the TC35896WBG to connect off-board I/Os can help simplify wiring, reduce cost and bulk, increase reliability and reduce EMI. Housed in a 2.5 x 2.5mm chip-scale package, the expander occupies minimal PCB space.
In addition to extending Toshiba’s family of I/O expanders to five devices, the TC35896WBG integrates ESD and EMI protection on-chip. ESD protection up to 8kV contact discharge (15kV air discharge) meets IEC 61000-4-2 level 4 and exceeds JEDEC JESD22. Attenuation better than -3dBm at 100MHz prevents radiated EMI interfering with sensitive components mounted nearby. Other devices in the family also have three PWM channels and 96 keyboard inputs, and provide a choice of 20 or 24 GPIOs as well as optional functions such as rotator controls, external reset and direct key support in packages up to 3.5 x 3.5mm BGA. One device is also available in a QFP44 package.
The keyboard connections enable the TC35896WBG to monitor a keypad matrix up to 8 x 12 keys. The three PWM channels can be used for LED backlight dimming or for simple motor control for smartphone vibrate modes. The PWMs can operate autonomously without main CPU interaction, which can help save processor cycles and also simplify power management by allowing greater use of sleep modes. The 20 GPIO channels can be used for numerous functions such as reset or enable signals. The host system configures the TC35896WBG conveniently via the I2C interface.