MAX6956

19-2414; Rev 2; 11/03 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander General Description The MAX6956 compact, serial-interfaced LED display driver/I/O expander provide microprocessors with up to 28 ports. Each port is individually user configurable to either a logic input, logic output, or common-anode (CA) LED constant-current segment driver. Each port configured as an LED segment driver behaves as a digitally controlled constant-current sink, with 16 equal current steps from 1.5mA to 24mA. The LED drivers are suitable for both discrete LEDs and CA numeric and alphanumeric LED digits. Each port configured as a general-purpose I/O (GPIO) can be either a push-pull logic output capable of sinking 10mA and sourcing 4.5mA, or a Schmitt logic input with optional internal pullup. Seven ports feature configurable transition detection logic, which generates an interrupt upon change of port logic level. The MAX6956 is controlled through an I2C™-compatible 2-wire serial interface, and uses four-level logic to allow 16 I 2C addresses from only 2 select pins. The MAX6956AAX and MAX6956ATL have 28 ports and are available in 36-pin SSOP and 40-pin thin QFN packages, respectively. The MAX6956AAI and MAX6956ANI have 20 ports and are available in 28-pin SSOP and 28-pin DIP packages, respectively. For an SPI-interfaced version, refer to the MAX6957 data sheet. For a lower cost pin-compatible port expander without the constant-current LED drive capabili...