SLVSFZ4A December   2020  – February 2021 TPS929121-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Device Bias and Power
        1. 8.3.1.1 Power Supply (SUPPLY)
        2. 8.3.1.2 5-V Low-Drop-Out Linear Regulator (VLDO)
        3. 8.3.1.3 Undervoltage Lockout (UVLO) and Power-On-Reset (POR)
        4. 8.3.1.4 Programmable Low Supply Warning
      2. 8.3.2 Constant Current Output
        1. 8.3.2.1 Reference Current With External Resistor (REF)
        2. 8.3.2.2 64-Step Programmable High-Side Constant-Current Output
      3. 8.3.3 PWM Dimming
        1. 8.3.3.1 PWM Dimming Frequency
        2. 8.3.3.2 PWM Generator
        3. 8.3.3.3 Linear Brightness Control
        4. 8.3.3.4 Exponential Brightness Control
        5. 8.3.3.5 External Clock Input for PWM Generator (CLK)
        6. 8.3.3.6 External PWM Input ( PWM0 and PWM1)
      4. 8.3.4 On-chip 8-bit Analog-to-Digital Converter (ADC)
      5. 8.3.5 Diagnostic and Protection in Normal State
        1. 8.3.5.1  Fault Masking
        2. 8.3.5.2  Supply Undervoltage Lockout Diagnostics in Normal State
        3. 8.3.5.3  Low-Supply Warning Diagnostics in Normal State
        4. 8.3.5.4  Reference Diagnostics in Normal State
        5. 8.3.5.5  Pre-Thermal Warning and Overtemperature Protection in Normal State
        6. 8.3.5.6  Communication Loss Diagnostic in Normal State
        7. 8.3.5.7  LED Open-Circuit Diagnostics in Normal State
        8. 8.3.5.8  LED Short-Circuit Diagnostics in Normal State
        9. 8.3.5.9  On-Demand Off-State Invisible Diagnostics
        10. 8.3.5.10 On-Demand Off-State Single-LED Short-Circuit (SS) Diagnostics
        11. 8.3.5.11 Automatic Single-LED Short-Circuit (AutoSS) Detection in Normal State
        12. 8.3.5.12 EEPROM CRC Error in Normal State
        13.       48
      6. 8.3.6 Diagnostic and Protection in Fail-Safe States
        1. 8.3.6.1 Fault Masking
        2. 8.3.6.2 Supply UVLO Diagnostics in Fail-Safe States
        3. 8.3.6.3 Low-supply Warning Diagnostics in Fail-Safe states
        4. 8.3.6.4 Reference Diagnostics at Fail-Safe States
        5. 8.3.6.5 Overtemperature Protection in Fail-Safe State
        6. 8.3.6.6 LED Open-circuit Diagnostics in Fail-Safe State
        7. 8.3.6.7 LED Short-circuit Diagnostics in Fail-Safe State
        8. 8.3.6.8 EEPROM CRC Error in Fail-safe State
        9.       58
    4. 8.4 Device Functional Modes
      1. 8.4.1 POR State
      2. 8.4.2 Initialization State
      3. 8.4.3 Normal State
      4. 8.4.4 Fail-Safe States
      5. 8.4.5 Program State
      6. 8.4.6 Programmable Output Failure State
      7. 8.4.7 ERR Output
      8. 8.4.8 Register Default Data
    5. 8.5 Programming
      1. 8.5.1 FlexWire Protocol
        1. 8.5.1.1 Protocol Overview
        2. 8.5.1.2 UART Interface Address Setting
        3. 8.5.1.3 Status Response
        4. 8.5.1.4 Synchronization Byte
        5. 8.5.1.5 Device Address Byte
        6. 8.5.1.6 Register Address Byte
        7. 8.5.1.7 Data Frame
        8.       77
        9. 8.5.1.8 CRC Frame
        10. 8.5.1.9 Burst Mode
      2. 8.5.2 Registers Lock
      3. 8.5.3 All Registers CRC Check
      4. 8.5.4 EEPROM Programming
        1. 8.5.4.1 Chip Selection by Pulling REF Pin High
        2. 8.5.4.2 Chip Selection by ADDR Pins configuration
        3. 8.5.4.3 EEPROM Register Access and Burn
        4. 8.5.4.4 EEPROM Program State Exit
        5. 8.5.4.5 Reading Back EEPROM
    6. 8.6 Register Maps
      1. 8.6.1 FullMap Registers
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Smart Rear Lamp With Distributed LED drivers
      2. 9.2.2 Design Requirements
      3. 9.2.3 Detailed Design Procedure
      4. 9.2.4 Application Curves
  10. 10Power Supply Recommendations
  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

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8.5.1.1 Protocol Overview

The FlexWire is a UART-based protocol supported by most microcontroller units (MCU), Each frame contains multiple bytes started with a synchronization byte. The synchronization byte allow LED drivers to synchronize with master MCU frequency, therefore saving the extra cost on high precision oscillators that are commonly used in UART / CAN interfaces. Each byte has 1 start bit, 8 data bits, 1 stop bit, no parity check. The LSB data follows the start bit as Figure 8-10 described. The FlexWire supports adaptive communication frequency ranging from 10kHz to 1MHz. The protocol supports master-slave with star-connected topology.

GUID-3A265E8A-68C4-41BB-8607-0811CDEEA1C5-low.gifFigure 8-10 One Byte Data Structure

The FlexWire is designed robust for automotive environment. Once the slave device receives a communication frame, it firstly verifies its CRC byte. Only when CRC is verified, the slave device sends out response frame and clears the watchdog timer. In addition, if one communication frame is interrupted in the middle without any bus toggling for a period longer than timeout timer T(FLTIMEOUT), the TPS929121-Q1 resets the communication and wait for next communication starting from synchronization byte. It is also required for idle period between bytes within T(FLTIMEOUT). The timeout timer T(FLTIMEOUT) is programmable by configuration register CONF_FLTIMEOUT. TI recommends using a longer timeout setting for low baud rate communication to avoid unintended timeout and using a shorter timeout setting for high baud rate communication.

If communication CRC check fails, the TPS929121-Q1 ignores the message without sending the feedback. The master does not receive any feedback if the communication is unsuccessful. In this case, the communication can be reset by keeping communication bus idle for T(FLTIMEOUT) , which forces the TPS929121-Q1 to clear its cache and be ready for new communication.

FlexWire supports both write and readback. Both write or readback communication supports burst mode for high throughput and single-byte mode. Figure 8-11 describes the frame structure of a typical single-byte write action. The master frame consists of SYNC, DEV_ADDR, REG_ADDR, DATA and CRC bytes. Once CRC is verified, the slave immediately feeds back ACK byte. Figure 8-12 describes the frame structure of a typical single-byte readback action. The master frame consists of SYNC, DEV_ADDR, REG_ADDR, and CRC bytes. Once CRC is verified, the slave immediately feeds back DATA and ACK bytes.

GUID-9B4668A5-18CC-481C-A8FA-6E39CFA48CF6-low.gifFigure 8-11 Single-Byte Write Command With Status Feedback
GUID-E164E2D1-E572-4BD1-94E3-D3F22C0EDF20-low.gifFigure 8-12 Single-Byte Readback Command
Table 8-6 Frame-Byte Description
BYTE NAMELENGTH (byte)DESCRIPTION
SYNC1Synchronization byte from master
DEV_ADDR1Device address bit, r/w, broadcast, burst mode
REG_ADDR1Register address
DATA_NVariable (1, 2, 4, 8)N-th byte data content
CRC1Cyclic redundancy check (CRC) for DEV_ADDR, REG_ADDR and all DATA bytes
STATUS1Acknowledgment (Return FLAG0 register value)
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