SCPS193C July   2010  – April 2014 TCA6424A


  1. Features
  2. Description
  3. Revision History
  4. Description (continued)
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Electrical Characteristics
    5. 6.5 I2C Interface Timing Requirements
    6. 6.6 Reset Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  7. Parameter Measurement Information
  8. Detailed Description
    1. 8.1 Overview
      1. 8.1.1 Voltage Translation
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 I/O Port
      2. 8.3.2 I2C Interface
      3. 8.3.3 Device Address
    4. 8.4 Programming
      1. 8.4.1 Power-On Reset
      2. 8.4.2 Reset Input (RESET)
      3. 8.4.3 Interrupt Output (INT)
      4. 8.4.4 Bus Transactions
        1. Writes
        2. Reads
    5. 8.5 Register Maps
      1. 8.5.1 Control Register and Command Byte
      2. 8.5.2 Register Descriptions
  9. Applications and Implementation
    1. 9.1 Typical Application
      1. 9.1.1 Minimizing ICC When I/Os Control LEDs
  10. 10Power Supply Recommendation
  11. 11Device and Documentation Support
    1. 11.1 Trademarks
    2. 11.2 Electrostatic Discharge Caution
    3. 11.3 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9 Applications and Implementation

9.1 Typical Application

Figure 29 shows an application in which the TCA6424A can be used.

A. Device address configured as 0100000 for this example.
B. P00 and P02–P10 are configured as inputs.
C. P01, P11–P17, and P20–P27 are configured as outputs.
D. Resistors are required for inputs (on P port) that may float. If a driver to an input will not let the input float, a resistor is not needed. Outputs (in the P port) do not need pullup resistors.
Figure 29. Typical Application

9.1.1 Minimizing ICC When I/Os Control LEDs

When the I/Os are used to control LEDs, normally they are connected to VCC through a resistor as shown in Figure 29. The LED acts as a diode so, when the LED is off, the I/O VIN is about 1.2 V less than VCC. The ΔICC parameter in Electrical Characteristics shows how ICC increases as VIN becomes lower than VCC. Designs that must minimize current consumption, such as battery power applications, should consider maintaining the I/O pins greater than or equal to VCC when the LED is off.

Figure 30 shows a high-value resistor in parallel with the LED. Figure 31 shows VCC less than the LED supply voltage by at least 1.2 V. Both of these methods maintain the I/O VIN at or above VCC and prevent additional supply current consumption when the LED is off.

hi_val_res_cps175.gifFigure 30. High-Value Resistor in Parallel With the LED
low_volt_cps175.gifFigure 31. Device Supplied by a Low Voltage