SLUSFA1 September   2024 TPS1214-Q1

ADVANCE INFORMATION  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 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 Switching Characteristics
  8. 7 Parameter Measurement Information
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Charge Pump and Gate Driver Output (VS, GATE, BST, SRC)
      2. 8.3.2 Capacitive Load Driving
        1. 8.3.2.1 Using Low Power Bypass FET (G Drive) for Load Capacitor Charging
        2. 8.3.2.2 Using Main FET (GATE drive) Gate Slew Rate Control
      3. 8.3.3 Overcurrent and Short-Circuit Protection
        1. 8.3.3.1 I2t-Based Overcurrent Protection
          1. 8.3.3.1.1 I2t-Based Overcurrent Protection With Auto-Retry
          2. 8.3.3.1.2 I2t-Based Overcurrent Protection With Latch-Off
        2. 8.3.3.2 Short-Circuit Protection
      4. 8.3.4 Analog Current Monitor Output (IMON)
      5. 8.3.5 NTC based Temperature Sensing (TMP) and Analog Monitor Output (ITMPO)
      6. 8.3.6 Fault Indication and Diagnosis (FLT, SCP_TEST)
      7. 8.3.7 Reverse Polarity Protection
      8. 8.3.8 Undervoltage Protection (UVLO)
    4. 8.4 Device Functional Modes
      1. 8.4.1 State Diagram
      2. 8.4.2 State Transition Timing Diagram
      3. 8.4.3 Power Down
      4. 8.4.4 Shutdown Mode
      5. 8.4.5 Low Power Mode (LPM)
      6. 8.4.6 Active Mode (AM)
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application 1: Driving Power at all times (PAAT) Loads With Automatic Load Wakeup
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
    3. 9.3 Typical Application 2: Driving Power at all times (PAAT) Loads With Automatic Load Wakeup and Output Bulk Capacitor Charging
      1. 9.3.1 Design Requirements
      2. 9.3.2 External Component Selection
      3. 9.3.3 Application Curves
    4. 9.4 Power Supply Recommendations
    5. 9.5 Layout
      1. 9.5.1 Layout Guidelines
      2. 9.5.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Device Support
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Support Resources
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information
    1. 12.1 Tape and Reel Information
    2. 12.2 Mechanical Data

Package Options

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

9.3.2 External Component Selection

By following similar design procedure as outlined in Section 8.2.2, the external component values are calculated as below:

  • RSNS = 0.5mΩ
  • RSET = 300Ω
  • RIMON = 18.2kΩ
  • RIOC = 23kΩ to set 40A as I2t protection start threshold
  • CI2t = 1µF to set 3000A2s as I2T factor
  • CBST = 150nF
  • RISCP = 2.55kΩ to set 130A as short-circuit protection threshold
  • CTMR = 47nF to set 1000ms auto-retry time
  • R3 and R4 are selected as 470kΩ and 107kΩ respectively to set VIN undervoltage lockout threshold at 6.5V

Programming the Load Wakeup Threshold, RBYPASS and Q3 Selection

During normal operation, the series resistor RBYPASS is used to set load wakeup current threshold. After VG_GOOD threshold is reached, the voltage between CS2+ and CS2– is compared against V(LWU) threshold (200mV typ) for load wakeup event. For selecting the MOSFET Q3, important electrical parameters are the maximum continuous drain current ID, the maximum drain-to-source voltage VDS(MAX), the maximum drain-to-source voltage VGS(MAX), and the drain-to-source ON resistance RDSON.

Based on the design requirements, BUK7J1R4-40H is selected and its ratings are:

40V VDS(MAX) and ±20V VGS(MAX)

RDS(ON) is 1.06mΩ typical at 10V VGS

RBYPASS resistor value can be selected using below equation:

Equation 30. R B Y P A S S   =   V ( L W U ) I L W U

To set 200mA load wakeup current, RBYPASS resistor is calculated to be 1Ω.

The average power rating of the bypass resistor can be calculated by following equation:

Equation 31. P A V G =   I L W U 2 ×   R BY PA SS

The average power dissipation of RBYPASS is calculated to be 0.04W.

The peak power dissipation in the bypass resistor is given by following equation:

Equation 32. P P E A K =   V B A T T _ M A X 2 R BY PA SS

The peak power dissipation of RBYPASS is calculated to be ~256W. The peak power dissipation time for power-up with short into LPM can be derived from t(LPM_SC) parameter (5μs) in electrical characteristics table.

Based on PPEAK and t(LPM_SC), 1Ω, 1%, 3/4W CRCW12101R00FKEAHP resistor is used to support both average and peak power dissipation for > t(LPM_SC) time. TI suggests the designer to share the entire power dissipation profile of bypass resistor with the resistor manufacturer and get their recommendation.

The peak short-circuit current in bypass path can be calculated based on following equation:

Equation 33. I P E A K _ B Y P A S S =   V B A T T _ M A X R BY PA SS

IPEAK_BYPASS is calculated to be 16A based on RBYPASS selected in Equation 30. TI suggest the designer to ensure that operating point (VBATT_MAX, IPEAK_BYPASS) for bypass path (Q3) is within the SOA curve for > t(LPM_SC) time.

Programming the Inrush Current, Rg and Cg Selection

Use following equation to calculate the IINRUSH:

Equation 34. I I N R U S H =   C L O A D ×   V B A T T_MAX T c h a r g e

IINRUSH calculated in Equation 34 should be always less than wakeup in short in low power mode (ILPM_SC) current which can be calculated using following equation:

Equation 35. I L P M _ S C =   2   V R BY P ASS

For 1Ω RBYPASS, ILPM_SC is calculated to be 2A which is less than IINRUSH.

Use following equation to calculate the required Cg based on IINRUSH calculated in Equation 34.

Equation 36. Cg = CLOAD × I(G)IINRUSH

Where, I(G) is 100µA (typical)

To set IINRUSH at 1.6A, Cg value is calculated to be ~50nF.

A series resistor Rg must be used in conjunction with Cg to limit the discharge current from Cg during turn-off .

The chosen value of Rg is 100Ω and Cg is 68nF.