Mobile I/O companion chips ease portable device designs

Santa Clara, Calif. — A mobile input/output (I/O) companion family from National Semiconductor Corp. enables designers to easily expand system functionality in portable products such as personal digital assistants, media players, instrumentation, medical equipment and mobile handsets. The LM8322 and LM8333 mobile I/O companion chips allow designers to re-partition their systems by offloading tasks from the processor and adding features through a reconfigurable set of simple commands, said National.

Enabling portable device manufacturers to differentiate their products through added features such as custom keyboards or special lighting, the modular single chips enable use of the same host processor and companion across multiple product versions. Both the off-the-shelf LM8322 and LM8333 ICs include embedded key-scan functions, I/O expansion and LED control capabilities.

Communication from the mobile I/O companion with the host processor is performed via a standard I2C compatible bus and interrupt signal that require only three pins, which provide designers with more options in placing the host processor on the board. In addition, a set of complex commands and scripts for pulse-width-modulation (PWM) signal generation allows the host to configure the mobile I/O companion's resources or trigger execution of commands.

Using the simple command set, the host processor can configure the LM8322 and LM8333 through an I2C compatible ACCESS.bus interface in slave mode up to 400 KHz. The fully tested and qualified companion chips are said to significantly reduce system design time and maintain accurate performance over the industrial temperature range of -40°C to 85° C.

The LM8322 supports keypad matrices up to 104 keys, while the LM8333 supports up to 72 keys. Both offer eight special-function keys that take priority in the key rolling sequence. The on-chip clock, power-on-reset and on-chip oscillator require minimal external circuitry to support the mobile I/O companion's operation, said National.

By offloading the keyboard scanning feature to the companion, the host processor can enter sleep mode and reduce system power consumption. When there is no activity on the host bus or keypad, the companion automatically enters stand-by mode, typically consuming 18 uW.

The LM8322 provides 1.62V-to-1.98V single-supply operation and up to 16 pins that can be configured as general-purpose I/O expansion for controlling additional peripherals. Its three independent, host-programmable PWM outputs can be used to generate more complex signals for adjusting a LED's brightness or other sophisticated lighting effects, said National.

Evaluation kits are available. The LM8322 evaluation kit provides hardware and software for evaluation in standalone mode or interfacing to a PC. The evaluation board also features several of National's complementary products for handheld devices including the LM75 digital temperature sensor, LP3906 dual high-current step-down DC-DC and linear regulator, LM3519 high-frequency boost white LED driver and LP2986 micropower, 200 mA ultra-low-dropout voltage regulator.

The LM8333 evaluation kit provides the hardware and software for keypad scanning implementation.

Pricing: The LM8322 in a 36-pin micro array package is priced at $2.65 each. The LM8333, available in both 32-pin LLP and 49-pin micro array packages, is priced at $1.95 and $2.05 each, respectively. All prices are in 1,000-unit quantities.
Availability: Available now.
Product information: LM8322 and LM8333, LM8322 evaluation kit and LM8333 evaluation kit

National Semiconductor , 1-408-721-5000,

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