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Programmable Low-Power GPIO/Keypad Controllers Simplify Interconnect Circuits For Large Qwerty Keypads

25th August 2011

Analog Devices

ES Admin

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Analog Devices introduced today the ADP5585 and ADP5589 GPIO (general-purpose input/output) port expander and keypad matrix controller for devices that require expanded I/O lines or mechanical keypads up to QWERTY size. The new GPIO/keypad controllers feature the industry’s lowest active current drain and integrated programmable logic/PWM (pulse-width modulator) in the smallest available package. These GPIO/keypad controllers save battery life in portable devices by consuming less than 30 µA (typical) when keys are pressed and less than 1 uA (typical) when the keys are idle.

The ADP5585 and ADP5589 simplify interface connectors by saving up to 10 I/O lines (ADP5585) and 19 I/O lines (ADP5589) to the main processor. Both keypad controllers support multiple, simultaneous key press detection and communicate presses and releases in a chronological order via a 16-byte FIFO. In addition to the built-in programmable logic devices, two programmable reset generators allow designers to program keys, GPIOs, and/or logic changes to generate a reset signal to restart a locked up processor. Both devices are available in small (ADP5585: 3.0 mm x 3.0 mm; ADP5589: 3.5 mm x 3.5 mm) and WLCSP packages (ADP5585: 1.59 mm x 1.59 mm; ADP5589: 1.99 mm x 1.99 mm).

The ADP5585 and ADP5589 are designed for devices with front-panel keypads that need to expand the number of GPIO ports without increasing pin count. Both devices free up the main processor from having to monitor the keypad, thereby reducing power consumption and increasing processor bandwidth for other functions. The new controllers handle all key scanning and decoding functions and use an interrupt line to flag the main processor when new key events have occurred. Both the ADP5585 and ADP5589 are equipped with FIFO registers that store up to 16 events which are then read back by the processor through an I2C -compatible interface. Evaluation boards and Linux software drivers are available to provide the necessary tools to implement new designs quickly and efficiently.

Key Features of the ADP5585 and ADP5589 GPIO/Keypad Controllers
Lower power consumption of 30 µA (typical) with keypad active, compared to 54 µA to 1000 µA available through alternative GPIO/keypad controllers
16-event FIFO simplifies reading of key, GPIO, and logic changes
10 configurable GPIO ports capable up to 30 keys can save up to 10 I/O lines to the main processor, simplifying interconnects (ADP5585)
19 configurable GPIO ports capable up to 96 keys can save up to 19 I/O lines to the main processor, simplifying interconnects (ADP5589)
I2C interface with Fast-mode Plus (Fm+) supports data rates up to 1 Mbps