Low-Voltage 8x16 Keyboard Scanner With HID over I2C Compliant Interface - TCA8424

TCA8424 (NRND)

Low-Voltage 8x16 Keyboard Scanner With HID over I2C Compliant Interface

 

Not Recommended for New Designs (NRND)

Replaced By TCA8418– The device has SIMILAR FUNCTIONALITY but is not functionally equivalent to the compared device.

TI does not recommend using this part in a new design. This product continues to be in production to support existing customers.

Description

This 128 key scan device is specifically targeted towards end equipment that runs on Windows 8 operating system. The device is fully compliant with the HID over I2C specification defined (ver 1.0) defined by Microsoft. The HID and report descriptors are hard coded into the device so that they don’t need to be programmed at production. The device also comes with a preprogrammed keyboard map that is compatible with most standard laptop/notebook keyboards. However, the device also available without a pre-programmed keyboard, so that any keyboard map may be written into it at production.

The device generates INPUT reports of standard 8-byte length with the 1st byte being the modifier byte. After the keyboard map is programmed into the device it automatically recognizes the row/column location of the modifier keys based on their usage code. It is capable of detecting and reporting up to six simultaneous key presses plus eight modifiers. It generates an input report on each key press and each key release.

The device also supports LED indicators that are standard on a keyboard. Different variations support 2,4 or 8 LED outputs. Each output has open drain architecture and is capable of sinking up to 12mA of current. The LEDs are controlled by a standard OUTPUT report as described in the HID over I2C standard.

Features

  • Operating Power-Supply Voltage Range of 1.65V to 3.6V
  • Supports FM+ I2C Operation up to 1MHz
  • Can Support up to 128 (8x16) Key Scan
  • Internal Power-On-Reset
  • Open Drain Open Drain Active Low INT Output
  • Noise Filter on SCL/SDA and Inputs
  • Open Drain Outputs Can Sink up to 12mA Current for LED
  • Hardware Coded HID and REPORT Descriptors
  • Available With Preprogrammed Keyboard Map
  • Software Reset per HID Over I2C Standard
  • Internal Pull-up Resistors Make Implementation Easy
    With no Need for External Components
  • HID Over I2C Commands Supported
    • RESET
    • GET REPORT
    • SET REPORT
    • SET POWER
  • Fixed Length 8-byte INPUT Report can Detect up to 6
    Simultaneous Key Presses Excluding Modifiers (CTRL, ALT,
    SHIFT)
  • INPUT Report Generated on Key Press and Release
  • Latch-Up Performance Exceeds 100 mA Per JESD 78, Class II
  • ESD Protection Exceeds JESD 22
    • 1000-V Human-Body Model (A114-A)

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