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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8.3.4 On-chip 8-bit Analog-to-Digital Converter (ADC)

The TPS929121-Q1 has integrated a successive-approximation-register (SAR) ADC for diagnostics. It routinely monitors supply voltage if the ADC is idle and stores SUPPLY conversion results into ADC_SUPPLY.

To manually read the voltage of an ADC channel as listed in Table 8-2, user must write the 5-bit register CONF_ADCCH to select channel. Once CONF_ADCCH register is written, the one time ADC conversion starts and clears FLAG_ADCDONE register. As long as the ADC conversion is completed, the ADC result is available in 8-bit register ADC_OUT and sets FLAG_ADCDONE to 1. Reading the ADC_OUT register also clears FLAG_ADCDONE, and the FLAG_ADCDONE is set to 0 after reading completion.

Because the TPS929121-Q1 supports PWM control for adjusting LED brightness, the voltage on OUT0 to OUT11 is like a pulse waveform. When the current output is enabled by setting CONF_ENCHx to 1, the ADC measures the voltage on assigned OUTx after the channel is turned on with t(diag_pulse) delay time, which is programmable by 4-bit register CONF_ODPW. When the channel is disabled by setting CONF_ENCHx to 0, the ADC samples the voltage on assigned OUTx at off state.

The analog value can be calculated based on the read back binary code with Equation 5 and Table 8-2.

Equation 5. GUID-55AD4B16-EAD8-43B8-9DF0-993AF803A17D-low.gif

where

  • ADC_OUT is decimal number from 0 to 255.
Table 8-2 ADC Channel
CHANNEL NO.CONF_ADCCHNAMEADC CALCULATION PARAMETER (a)ADC CALCULATION PARAMETER (k)COMMENT
000hREF0.007 V0.0101 V/LSBReference voltage
101hSUPPLY0.2878 V0.1583 V/LSBSupply voltage
202hVLDO0.0465 V0.022 V/LSB5-V LDO output voltage
303hTEMPSNS–304.7 °C2.463°C/LSBInternal temperature sensor
404hIREF0.7592 µA0.7461 µA/LSBReference current
505hMAXOUT0.2878 V0.1583 V/LSBMaximum channel output voltage
6-1506h - 0FhRESERVEDRESERVEDRESERVEDRESERVED
1610hOUT00.2878 V0.1583 V/LSBOutput voltage channel 0
1711hOUT1Output voltage channel 1
1812hOUT2Output voltage channel 2
1913hOUT3Output voltage channel 3
2014hOUT4Output voltage channel 4
2115hOUT5Output voltage channel 5
2216hOUT6Output voltage channel 6
2317hOUT7Output voltage channel 7
2418hOUT8Output voltage channel 8
2519hOUT9Output voltage channel 9
261AhOUT10Output voltage channel 10
271BhOUT11Output voltage channel 11
281ChRESERVEDRESERVEDRESERVEDRESERVED
291DhRESERVEDRESERVEDRESERVEDRESERVED
301EhRESERVEDRESERVEDRESERVEDRESERVED
311FhRESERVEDRESERVEDRESERVEDRESERVED

The TPS929121-Q1 also provides ADC auto-scan mode for single-led short-circuit diagnostics. The detail description for auto-scan mode can be found in On-Demand Off-State Single-LED Short-Circuit (SS) Diagnostics.

In ADC auto-scan mode, If MAXOUT channel is selected by writing 05h to CONF_ADCCH, the maximum voltage of OUT0 to OUT11 is recorded into ADC_OUT register. The maximum channel output voltage is available after at least one output PWM cycle is completed. Based on the measured maximum output voltage and supply voltage, microcontroller is able to regulate supply voltage from previous power stage to minimize the power consumption on the TPS929121-Q1. Basically microcontroller needs to program the output voltage of previous power stage to be just higher than the measured maximum channel output voltage plus the required dropout voltage V(OUT_drop) of the TPS929121-Q1. In this way, the TPS929121-Q1 takes minimum power consumption, and overall power efficiency is optimized.
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