GENERAL DESCRIPTION
The ADP5588 is an I/O port expander and keypad matrix
designed for QWERTY type phones that require a large keypad
matrix and expanded I/O lines. I/O expander ICs are used in
mobile platforms as a solution to the limited number of GPIOs
available in the main processor. In its small 4 mm × 4 mm package, the ADP5588 contains
enough power to handle all key scanning and decoding and flag
the processor of key presses and releases via the I2C® interface
and interrupt. It frees the main microprocessor from having to monitor the keypad, thereby minimizing current drain and
increasing processor bandwidth. It is also equipped with a buffer/FIFO and key event counter to handle and keep track of up to 10 unprocessed key or GPI events with overflow wrap and interrupt capability. The ADP5588 has a keylock capability with an option to trigger
or not trigger an interrupt at key presses and releases. All com-
munication to the main processor is done using one interrupt line
and two I2C-compatible interface lines. The ADP5588 can be
configured to have a keypad matrix of up to 8 rows × 10 columns
(a maximum of 80 keys).
When used for smaller keypad matrices, unused row and column pins can be reconfigured to act as general-purpose
inputs, outputs, or light sensor inputs. R0, R1, R2, R3, R4, R5, R6,
and R7 denote the row pins of the matrix, while C0, C1, C2, C3,
C4, C5, C6, C7, C8, and C9 denote the column pins. At power-up, all rows and columns default as GPIs and must be programmed to
function as part of the keypad matrix, GPOs, or light sensor inputs. In addition to keypad and GPIO functionalities, C8 and C9 can
also be configured as light sensor inputs. When configured as keypad lines, the function of the C8 and
C9 lines is straightforward: the control interface disconnects
these lines from the comparator inputs, disables the light sensor comparator, and connects them to the keypad columns of the
keypad matrix. When used as light sensor comparator inputs, the control interface disconnects these pins from the keypad,
enables the comparators, and connects these lines to the com-
parator inputs. Two external capacitors (0.1 μF) are required when these pins are configured as light sensor inputs. When used as GPIOs, these pins are removed from the keypad and the light sensor interface, and the light sensor comparators are disabled, along with the logic for the sensors.

FEATURES 18-GPIO port expander or 10 × 8 keypad matrix
GPIOs configurable to GPIs, GPOs, and keypad rows or
columns Dual light sensor inputs (C8 and C9) I2C interface I2C register read autoincrement
1.8 V to 3.0 V operation
Keypad lock capability
Open-drain interrupt output Key press and key release interrupts
GPI interrupt with level programmability Programmable pull-ups
Key event counter with overflow interrupt
50 μs debounce on the reset line and GPIs
1 μA typical idle current, 55 μA typical polling current drain for one key press
Small 4 mm × 4 mm LFCSP package

APPLICATIONS
Keypad and I/O expander designed for QWERTY type phones that require a large keypad matrix