Semtech has released the SX1508 and SX1509, two advanced, low-voltage, level shifting I/O expanders that come in 8 - and 16-channels, respectively, with an advanced LED driver and keypad engine capability.
With an operating voltage range from 1.5 to 3.6V, these devices connect easily to advanced low-core, voltage chipsets in hand-held applications, and eliminate the need for extra level-translating circuits. On the output side, dual voltage I/O rails provide level shifting down to 1.2V, as well as I/O interface with two different logic levels.
The devices are complete, low-voltage GPIOs that enable direct I/O and feature expansion to low-core voltage chipsets that are found in battery-powered devices such as cell phones, MP3 players, and digital still cameras. Each true bi-directional style, 15mA rated I/O is integrated with a high-resolution, 256-step LED driver for enhanced lighting effect such as RGB colour mixing. The intensity of each channel can be programmed independently using a linear or logarithmic function (optimised for human vision). These advanced LED drivers also feature automatic blinking and breathing (fade-in/fade-out) control, thus minimising the software loading from the host controller.
These devices are equipped with an intelligent, on-chip keypad engine that supports key matrix scanning up to 8x8 (64 keys) with auto sleep/wake up to reduce the system EMI noise and power consumption. Scan time and debounce time can also be adjusted to address the needs for different key matrix applications.
The devices are specially designed with smart features to reduce the host controller interaction in portable applications. The unique breathing control in the LED driver enables continuous fade-in and fade-out lighting effects while the host controller is asleep. Keypad scanning can also be easily done with the on-chip keypad engine without any significant system power penalty. The I2C SX1508 is offered in a small, 3x3mm, 20 QFN package while the SX1509 comes in a space-saving 4x4mm, 28 QFN package. SPI versions are also available for both the devices. The devices can operate over the extended -40 to +85°C temperature range.
The features of the devices include built-in clock management (internal 2MHz or external clock input, 7 clock values); open drain active low interrupt output; dedicated hardware reset input; 400kHz I²C interface with four user-selectable I²C addresses; and low current consumption of 1uA.
