SCPS204D January   2014  – November 2019 TCA9545A

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Application Diagram
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 I2C Interface Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Interrupt and Reset Timing Requirements
    9. 6.9 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
    4. 8.4 Device Functional Modes
      1. 8.4.1 RESET Input
      2. 8.4.2 Power-On Reset
    5. 8.5 Programming
      1. 8.5.1 I2C Interface
    6. 8.6 Control Register
      1. 8.6.1 Device Address
      2. 8.6.2 Control Register Description
      3. 8.6.3 Control Register Definition
      4. 8.6.4 Interrupt Handling
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 TCA9545A Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 Power-On Reset Requirements
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Support Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

10.1 Power-On Reset Requirements

In the event of a glitch or data corruption, TCA9545A can be reset to its default conditions by using the power-on reset feature. Power-on reset requires that the device go through a power cycle to be completely reset. This reset also happens when the device is powered on for the first time in an application.

A power-on reset is shown in Figure 20.

TCA9545A pwron02_cps204.gifFigure 20. VCC is Lowered Below the POR Threshold, Then Ramped Back Up to VCC

Table 3 specifies the performance of the power-on reset feature for TCA9545A for both types of power-on reset.

Table 3. Recommended Supply Sequencing And Ramp Rates(1)

PARAMETER MIN TYP MAX UNIT
VCC_FT Fall time See Figure 20 1 100 ms
VCC_RT Rise time See Figure 20 0.1 100 ms
VCC_TRR Time to re-ramp (when VCC drops below VPORF(min) – 50 mV or when VCC drops to GND) See Figure 20 40 μs
VCC_GH Level that VCC can glitch down to, but not cause a functional disruption when VCC_GW = 1 μs See Figure 21 1.2 V
VCC_GW Glitch width that will not cause a functional disruption when VCC_GH = 0.5 × VCC See Figure 21 10 μs
VPORF Voltage trip point of POR on falling VCC See Figure 22 0.8 1.25 V
VPORR Voltage trip point of POR on rising VCC See Figure 22 1.05 1.5 V
(1) All supply sequencing and ramp rate values are measured at TA = 25°C

Glitches in the power supply can also affect the power-on reset performance of this device. The glitch width (VCC_GW) and height (VCC_GH) are dependent on each other. The bypass capacitance, source impedance, and device impedance are factors that affect power-on reset performance. Figure 21 and Table 3 provide more information on how to measure these specifications.

TCA9545A pwron03_cps204.gifFigure 21. Glitch Width and Glitch Height

VPOR is critical to the power-on reset. VPOR is the voltage level at which the reset condition is released and all the registers and the I2C/SMBus state machine are initialized to their default states. The value of VPOR differs based on the VCC being lowered to or from 0. Figure 22 and Table 3 provide more details on this specification.

TCA9545A pwron04_cps204.gifFigure 22. VPOR