Here are two interface-I/O Expanders offered for you to choose from:
One is PCA9536DP118
http://www.kynix.com/Detail/6231/PCA9536DP118.html
The PCA9536 is an 8-pin CMOS device that provides 4 bits of General Purpose parallel
Input/Output (GPIO) expansion for I2C-bus/SMBus applications and was developed to
enhance the NXP Semiconductors family of I2C-bus I/O expanders. I/O expanders
provide a simple solution when additional I/O is needed for ACPI power switches,
sensors, push buttons, LEDs, fans, etc.
Features
1.4-bit I2C-bus GPIO
2. Operating power supply voltage range of 2.3 V to 5.5 V
3. 5 V tolerant I/Os
4. Polarity Inversion register
5. Low standby current
6. Noise filter on SCL/SDA inputs
7. No glitch on power-up
8. Internal power-on reset
9. 4 I/O pins which default to 4 inputs with 100 kΩ internal pull-up resistor
10. 0 Hz to 400 kHz clock frequency
11. ESD protection exceeds 2000 V HBM per JESD22-A114, 200 V MM per
12. JESD22-A115 and 1000 V CDM per JESD22-C101
13. Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA
14. Packages offered: SO8, TSSOP8 (MSOP8), HVSON8
the other is SX1509QBIULTRT
http://www.kynix.com/Detail/11386/SX1509QBIULTRT.html
The SX1508QB and SX1509QB are complete ultra low voltage General Purpose parallel Input/Output (GPIO) expanders ideal for low power handheld
battery powered equipment. This family of GPIOs comes in 8-, 16-channel configuration and allows easy serial expansion of I/O through a standard
400kHz I2C interface. GPIO devices can provide additional control and monitoring when the microcontroller or chipset has insufficient I/O ports, or
in systems where serial communication and control from a remote location is advantageous.
Features
1.2V to 3.6V Low Operating Voltage with Dual
Independent I/O Rails (VCC1, VCC2)
Enable Direct Level Shifting Between I/O
Banks and Host Controller
• 5.5V Tolerant I/Os, Up to 15mA Output Sink on
All I/Os (No Total Sink Current Limit)
• Integrated LED Driver for Enhanced Lighting
Intensity Control (256-step PWM)
Blink Control (224 On/Off values)
Breathing Control (224 Fade In/Out values)
• On-Chip Keypad Scanning Engine
Support Up to 8x8 Matrix (64 Keys)
Configurable Input Debouncer
• 8/16 Channels of True Bi-directional Style I/O
Programmable Pull-up/Pull-down
Push/Pull or Open-drain outputs
Programmable Polarity
• Open Drain Active Low Interrupt Output (NINT)
Bit Maskable
Programmable Edge Sensitivity
• Built-in Clock Management (Internal 2MHz
Oscillator/External Clock Input, 7 clock values)
OSCIO can be Configured as GPO
• 400kHz I2C Compatible Slave Interface
• 4 User-Selectable I²C Slave Addresses
• Power-On Reset and Reset Input (NRESET)
• Ultra Low Current Consumption: 1uA Typ
• -40°C to +85°C Operating Temperature Range
• Up to 2kV HBM ESD Protection
• Small Footprint Packages
• Pb & Halogen Free, RoHS/WEEE compliant
I have been puzzled about this topic for couples of months. Today, I come to this forum to turn to you to discuss what interface-I/O expanders you like best. I need your help, so please help me do an unselectable choice.
What is your idea ? Do you agree with my ideas ? Any of your ideas would be highly appreciated.
thanks in advance.