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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8.4.7 ERR Output

The ERR pin is a programmable fault indicator pin. It can be used as an interrupt output to master controller in case there is any fault in normal mode. In fail-safe states, the ERR pin can be used as an output to other ERR pin of other TPS929121-Q1 to realize one-fails-all-fail at system level. The ERR pin is a open-drain output with current limit up to I(pd_ERR). TI recommends a <10-kΩ external pullup resistor from the ERR pin to the same IO voltage of master controller.

In normal state, when a fault is triggered, depending on the fault type, the ERR pin is either pulled down constantly or pulled down for a single pulse. Once an ERR output is triggered, the master controller must take action to deal with the failure and reset the fault flag. Otherwise the ERR pin cannot be pulled down again. For non-critical faults, the TPS929121-Q1 pulls down the ERR pin with a duration of 50 µs and release; for critical faults, device constantly pulls down ERR as described in Table 8-3. In normal state, basically the TPS929121-Q1 only reports the faults to the master controller for most of the failure and takes no actions except supply or LDO UVLO and overtemperature. The master controller determine what action to take according to the type of the failure.

The TPS929121-Q1 provides a forced-error feature to validate the error feedback-loop integrity in normal state. In normal state, if microcontroller sets CONF_FORCEERR to 1, the FLAG_ERR is set 1 and pulls down ERR output with a pulse of 50 µs accordingly. The CONF_FORCEERR automatically returns to 0.

In fail-safe states, the ERR pin is used as fault bus. When there is any output failure reported, the ERR is pulled down by internal current sink I(pd_ERR). The TPS929121-Q1 monitors the voltage of the ERR pin. If the one-fails-all-fail diagnostics is enabled by setting register EEP_OFAF to 1, all current output channels are turned off, as well as diagnostics, when the ERR pin voltage is low. If register EEP_OFAF is 0, the device only turns off the failed channel with alive channels diagnostics enabled.

Table 8-5 One-Fails-All-Fail Feature in Fail-safe States
EEP_OFAF = 1 EEP_OFAF = 0
ERR = 0All OUT channel OFF if any one OUT failure is detectedOnly detected failed OUT OFF
ERR = 1Only failed OUT OFFOnly detected failed OUT OFF

If multiple TPS929121-Q1 devices are used in one application, tying the ERR pins together achieves the one-fails-all-fail behavior in fail-safe states without master controlling. Any one of TPS929121-Q1 reports fault by pulling the ERR pin to low, and the low voltage on ERR bus is detected by other TPS929121-Q1 as Figure 8-9 illustrated. If the register EEP_OFAF is set to 1 for all TPS929121-Q1 devices having the ERR pins tied together, all TPS929121-Q1 devices turn off current for all output channels.

GUID-20201117-CA0I-FBC0-NMJF-HQ8CGHSGDQLZ-low.gif Figure 8-9 ERR Internal Block Diagram