I/O Expander can easily expand the functions such as GPIOs, Keypads, LED controls and timers to the existing systems.
The IO Expander addresses some of the mechanical and electrical challenges that arise during the design of a modern high-end clam-shell or advanced feature phone.  By conception, typical Baseband or application LSI packages are kept at a minimum pin count.  Very often the pin multiplexers have to be incorporated into those LSI to compromise functionality or flexibility with respect to the cost. 
Moreover signals of the main processors must often be transported over a mechanical hinge to remote areas of the mobile phone. The number of wires being routed over these hinges should be minimised due to the mechanical properties of the hinge. Flexible IO Expander+ allows to overcome those limits. Its flexible expansion capabilities makes it particularly useful for entire platform roadmaps with different functional extensions for each member of the platform family.  Read more... (pdf 275KB).

I/O Expander Concept

The I/O Expander allows extended I/O functions controlled via a simple and easy to integrate I2C interface linked to your host CPU.  It allows an easy realization of additional digital inputs and outputs, also for time critical input signals that can generate interrupts to the host.  It features intelligent control of keypads and of normal switches, it incorporates a variety of timer and PWM functions for LED or other digitally controlled peripherals.  All this enables manufacturers to quickly launch spin-off models and other variations of their hardware, if their host CPU cannot support those function anymore.

Application Benefits

• Reduction of mechanical stress on hinges in clamp shell phones
  Flexible IO Expander+ reduces dramatically the number of wires over movable parts.
• Full support of low power operation from a 32kHz signal clock
  Flexible IO Expander+ requires only a 32kHz clock signal for the full operation which can be generated internally or externally.  The current consumption of this LSI is highly optimized for the use in mobile phones.
• I/O Expansion of baseband processors
  Baseband or application chip packages are often limited in the amount of balls for basic periphery.  Due to this limitation, required IO functionality might be missing.  Flexible IO Expander+ provides up to 24 general purpose Input/Output pins at the location, where needed.
• Expand your mobile phone with up to 96 keys
  Flexible IO Expander+ provides the full flexibility to handle various keyboard configuration from 2x2 to 8x12.  Also single keys are supported.  The Keyboard module detects up to four simultaneous key presses and de-bouncing is done in hardware.  The LSI is able to detect key presses and releases.
• PWM signal generation for LED and vibrator control
  Three independent versatile timers can be programmed to generate modulated PWM signals without interaction of the host processor during runtime.
• Rotator wheel interface in TC35892XBG
  The rotator wheel state machine counts up or down rotations of an external rotator wheel.  The interface is able to handle rotator devices with three dedicated click positions.
• Additional glue logic to the phone in TC35892XBG
  The additional configurable on chip glue logic allows to combine up to four input signals.
• EMI reduction on wires through hinge.
  Flexible IO Expander+ can operate only from a 32kHz clock. No high speed clock is required for stand-by or operation mode.

Features

• Low-power operation
• I2C interface; Max. 8×12 key matrix; PWM timer; general-purpose I/O pins (GPIO)
• Up to 24 general-purpose I/O pins
• Read more... (pdf 391KB)

IO Expander Product Family

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Further Information

MPD (Mobile Peripheral Devices)

• Camera Bridge
• Display Bridge/Hub
• Mobile TV-Out/Display Buffer