SLVSF65A December   2020  – May 2021 TPS92633-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  Power Supply (SUPPLY)
        1. 7.3.1.1 Power-On Reset
        2. 7.3.1.2 Supply Current in Fault Mode
      2. 7.3.2  Enable and Shutdown (EN)
      3. 7.3.3  Reference Current (IREF)
      4. 7.3.4  Constant-Current Output and Setting (INx)
      5. 7.3.5  Analog Current Control (ICTRL)
        1. 7.3.5.1 Off-Board Brightness Binning Resistor
        2. 7.3.5.2 NTC Resistor
      6. 7.3.6  Thermal Sharing Resistor (OUTx and RESx)
      7. 7.3.7  PWM Control (PWMx)
      8. 7.3.8  Supply Control
      9. 7.3.9  Diagnostics
        1. 7.3.9.1 IREF Short-to-GND Detection
        2. 7.3.9.2 IREF Open Detection
        3. 7.3.9.3 LED Short-to-GND Detection
        4. 7.3.9.4 LED Open-Circuit Detection
        5. 7.3.9.5 Single LED Short-Circuit Detection (SLS_REF)
        6. 7.3.9.6 LED Open-Circuit and Single LED Short-Circuit Detection Enable (DIAGEN)
        7. 7.3.9.7 Low Dropout Operation
        8. 7.3.9.8 Over-Temperature Protection
      10. 7.3.10 FAULT Bus Output With One-Fails–All-Fail
      11. 7.3.11 FAULT Table
      12. 7.3.12 LED Fault Summary
      13. 7.3.13 IO Pins Inner Connection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Undervoltage Lockout, V(SUPPLY) < V(POR_rising)
      2. 7.4.2 Normal Operation V(SUPPLY) ≥ 4.5 V
      3. 7.4.3 Low-Voltage Dropout Operation
      4. 7.4.4 Fault Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 BCM Controlled Rear Lamp with One-Fails-All-Fail Setup
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Independent PWM Controlled Rear Lamp with Off Board LED and Binning Resistor
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 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

8.2.2.2 Detailed Design Procedure

TI recommends to short the SLS_REF pin to GND when single-LED short-circuit is not required.

STEP 1: Determine the reference current setting resistor, R(IREF), by using Equation 15.

Equation 15. GUID-6C55E1B2-63C5-470D-B74E-FBEFA2C1B199-low.gif

where

  • V(IREF) = 1.235 V (typical)
  • I(IREF) = 200 µA (recommended for off-board binning resistor)

TI recommends 200-µA current for reference current, I(IREF) if the ICTRL resistor is placed in the other board with TPS92633-Q1. The calculated result for R(IREF) is 6.19 kΩ when I(IREF) = 200 µA.

STEP 2: Design the ICTRL resistor, R(ICTRL1) and R(ICTRL2), for setting the regulation voltage, V(CS_REG), by using Equation 16.

Equation 16. GUID-92A3689D-3887-48EE-850F-4FFF768B5C15-low.gif

where

  • I(IREF) = 200 µA (recommended for off-board binning resistor)

TI recommends 80 mV, 120 mV and 160 mV or reference voltage across current sensing resistor, R(SNSx), for three different brightness binning LED. The calculated result for R(ICTRL1) and R(ICTRL2) for different brightness bin LED is listed in Table 8-1. It is recommended to choose as large as possible R(ICTRL1) to achieve the highest noise immunity.

STEP 3: Determine the current sensing resistor, R(SNSx), by using Equation 17.

Equation 17. GUID-9AEC9A36-E681-42D7-AB48-0797DC6F05E0-low.gif

where

  • V(IREF) = 1.235 V (typical)
  • R(IREF) = 6.19 kΩ

According to design requirements, output current for each channel is same so that the R(SNS1) = R(SNS2) = R(SNS3). The calculated result for R(SNSx) is listed in Table 8-1.

Table 8-1 Calculated Resistor Table
LED Brightness Group ALED Brightness Group BLED Brightness Group C
I(OUTx_Tot)50 mA75 mA100 mA
V(CS_REG)80 mV120 mV160 mV
R(ICTRL1) + R(ICTRL2)272 Ω408 Ω544 Ω
R(ICTRL1)270 Ω
R(ICTRL2)2 Ω140 Ω274 Ω
R(SNSx)1.6 Ω

STEP 4: Design the current distribution between I(OUTx) and I(RESx) and calculate the current sharing resistor, R(RESx), by using Equation 18. The R(RESx) value actually decides the current distribution for I(OUTx) path and I(RESx) path, basic principle is to design the R(RESx) to consume appropriate 50% total power dissipation at typical supply operating voltage.

Equation 18. GUID-7CB7D84D-D701-4DF4-A0C8-CD82E6E47EAB-low.gif

where

  • V(SUPPLY) = 12 V (typical)
  • I(OUTx_Tot) = 100 mA (maximum)

The calculated result for R(RESx) resistor value including R(RES1), R(RES2) and R(RES3) is 152 Ω when V(OUTx) is typical 2 × 2.2 V = 4.4 V.

STEP 5: Design the threshold voltage of SUPPLY to enable the LED open-circuit and single-LED short-circuit diagnostics, and calculate voltage divider resistor value for R1 and R2 on DIAGEN pin.

The maximum forward voltage of LED-string is 2 × 2.5 V = 5 V. To avoid the open-circuit fault reported in low-dropout operation conditions, additional headroom between SUPPLY and OUTx needs to be considered. The TPS92633-Q1 device must disable open-circuit detection when the supply voltage is below LED-string maximum forward voltage plus V(OPEN_th_rising) and V(CS_REG). The voltage divider resistor, R1 and R2 value can be calculated by Equation 19.

Equation 19. GUID-6B29B95C-25ED-4458-809B-E90C8BB2EA2E-low.gif

where

  • V(OPEN_th_rising) = 210 mV (maximum)
  • V(CS_REG) = 160 mV (maximum)
  • VIL(DIAGEN) = 1.045 V (minimum)
  • R2 = 10 kΩ (recommended)

The calculated result for R1 is 41.2 kΩ when V(OUTx) maximum voltage is 5 V and V(CS_REG) is 160 mV maximum.