SLVSE03B April   2019  – February 2021 TPS929120-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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 Timing Requirements
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Device Bias and Power
        1. 7.3.1.1 Power Supply (SUPPLY)
        2. 7.3.1.2 5-V Low-Drop-Out Linear Regulator (VLDO)
        3. 7.3.1.3 Undervoltage Lockout (UVLO) and Power-On-Reset (POR)
        4. 7.3.1.4 Programmable Low Supply Warning
      2. 7.3.2 Constant Current Output
        1. 7.3.2.1 Reference Current With External Resistor (REF)
        2. 7.3.2.2 64-Step Programmable High-Side Constant-Current Output
      3. 7.3.3 PWM Dimming
        1. 7.3.3.1 PWM Dimming Frequency
        2. 7.3.3.2 PWM Generator
        3. 7.3.3.3 Linear Brightness Control
        4. 7.3.3.4 Exponential Brightness Control
        5. 7.3.3.5 External Clock Input for PWM Generator (CLK)
        6. 7.3.3.6 External PWM Input ( PWM0 and PWM1)
      4. 7.3.4 On-chip 8-bit Analog-to-Digital Converter (ADC)
      5. 7.3.5 Diagnostic and Protection in Normal State
        1. 7.3.5.1  Fault Masking
        2. 7.3.5.2  Supply Undervoltage Lockout Diagnostics in Normal State
        3. 7.3.5.3  Low-Supply Warning Diagnostics in Normal State
        4. 7.3.5.4  Reference Diagnostics in Normal State
        5. 7.3.5.5  Pre-Thermal Warning and Overtemperature Protection in Normal State
        6. 7.3.5.6  Communication Loss Diagnostic in Normal State
        7. 7.3.5.7  LED Open-Circuit Diagnostics in Normal State
        8. 7.3.5.8  LED Short-circuit Diagnostics in Normal State
        9. 7.3.5.9  On-Demand Off-State Invisible Diagnostics
        10. 7.3.5.10 On-Demand Off-State Single-LED Short-Circuit (SS) Diagnostics
        11. 7.3.5.11 Automatic Single-LED Short-Circuit (AutoSS) Detection in Normal State
        12. 7.3.5.12 EEPROM CRC Error in Normal State
        13.       47
      6. 7.3.6 Diagnostic and Protection in Fail-Safe States
        1. 7.3.6.1 Fault Masking
        2. 7.3.6.2 Supply UVLO Diagnostics in Fail-Safe States
        3. 7.3.6.3 Low-supply Warning Diagnostics in Fail-Safe states
        4. 7.3.6.4 Reference Diagnostics at Fail-Safe States
        5. 7.3.6.5 Overtemperature Protection in Fail-Safe State
        6. 7.3.6.6 LED Open-circuit Diagnostics in Fail-Safe State
        7. 7.3.6.7 LED Short-circuit Diagnostics in Fail-safe State
        8. 7.3.6.8 EEPROM CRC Error in Fail-safe State
        9.       57
    4. 7.4 Device Functional Modes
      1. 7.4.1 POR State
      2. 7.4.2 Initialization State
      3. 7.4.3 Normal State
      4. 7.4.4 Fail-Safe States
      5. 7.4.5 Program State
      6. 7.4.6 Programmable Output Failure State
      7. 7.4.7 ERR Output
      8. 7.4.8 Register Default Data
    5. 7.5 Programming
      1. 7.5.1 FlexWire Protocol
        1. 7.5.1.1 Protocol Overview
        2. 7.5.1.2 UART Interface Address Setting
        3. 7.5.1.3 Status Response
        4. 7.5.1.4 Synchronization Byte
        5. 7.5.1.5 Device Address Byte
        6. 7.5.1.6 Register Address Byte
        7. 7.5.1.7 Data Frame
        8.       76
        9. 7.5.1.8 CRC Frame
        10. 7.5.1.9 Burst Mode
      2. 7.5.2 Registers Lock
      3. 7.5.3 All Registers CRC Check
      4. 7.5.4 EEPROM Programming
        1. 7.5.4.1 Chip Selection by Pulling REF Pin High
        2. 7.5.4.2 Chip Selection by ADDR Pins configuration
        3. 7.5.4.3 EEPROM Register Access and Burn
        4. 7.5.4.4 EEPROM Program State Exit
        5. 7.5.4.5 Reading Back EEPROM
    6. 7.6 Register Maps
      1. 7.6.1 FullMap Registers
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Smart Rear Lamp With Distributed LED drivers
      2. 8.2.2 Design Requirements
      3. 8.2.3 Detailed Design Procedure
      4. 8.2.4 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.5.9 On-Demand Off-State Invisible Diagnostics

It is commonly required to ensure there is no fault on each LED load before lighting them up, especially for LED animation. Otherwise, the LED fault is detected in the middle of the admiration pattern, which results a random and uncertain failure animation pattern. The TPS929120-Q1 provides a solution to diagnose the LED open-circuit or LED short-circuit fault without lighting up the LEDs. With this feature, the master controller can initiate the on-demand invisible diagnostics before commencing the animation sequence. If one of the channel fails, the device is able to detect it immediately instead of only when the fault channel is turned on in traditional diagnostics mode. To initiate the on-demand invisible diagnostics, the master controller writes register CONF_INVDIAGSTART to 1. The register CONF_INVDIAGSTART returns to 0 automatically in the next clock cycle. Once the diagnostics started, the on-demand diagnostics ready flag FLAG_ODREADY is cleared to 0. Once the diagnostics finished, the FLAG_ODREADY is set to 1. If any channel has output failures, its on-demand diagnostic flag FLAG_ODDIAGCHx is set 1.

To ensure the invisibility of the diagnostics, the TPS929120-Q1 outputs only a small DC current in short period to each output channel and detects if there is any LED open-circuit or LED short-circuit failures. The output DC current I(ODIOUT) can be adjusted to a proper value by setting the DC current CONF_ODIOUT and ignoring the DC current setup by register CONF_IOUTx. The pulse-width T(ODPW) of output DC current can be programmable by CONF_ODPW and neglecting duty cycle configuration by register CONF_PWMOUTx. At the end of the current output pulse, if there is any LED open-circuit fault as Section 7.3.5.7 described, the TPS929120-Q1 pulls the ERR pin down with one pulsed current sink for 50 µs to report fault and set flag registers including FLAG_OPENCHx, FLAG_OUT and FLAG_ERR to 1. If there is any LED short-circuit fault as Section 7.3.5.8 described, the TPS929120-Q1 pulls the ERR pin down with one pulsed current sink for 50 µs to report fault and set flag registers including FLAG_SHORTCHx, FLAG_OUT and FLAG_ERR to 1. The master controller must write 1 to CLR_FAULT register to clear fault flags after the fault removal is verified by another on-demand off-state invisible diagnostics. TI recommends turning off all output channels by set CONF_ENCHx to 0 before invisible diagnostics.

For invisible diagnostics mode, it is required to have a short-pulse and low output current to avoid lighting up LEDs. However, the diagnostics are strongly affected by large loading capacitance. If the invisible diagnostics pulse failed to charge output capacitance above short-circuit threshold, the device reports a false short-circuit failure. If pulse failed to charge output above open-circuit threshold at maximum supply voltage, the device does not report open-circuit fault correctly. Thus, the DC current and period of the detection pulse must be carefully selected based on the capacitance value at output in real application.

GUID-4265FA0D-B420-4C1D-A688-0585F5C47703-low.gifFigure 7-4 Programmable Invisible Diagnostics Timing Sequence