ZHCSQI6C May   2022  – October 2023 TPS62870-Q1 , TPS62871-Q1 , TPS62872-Q1 , TPS62873-Q1

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  5. 4 Revision History
  6. 5 说明（续）
  7. 6 Device Options
  8. 7 Pin Configuration and Functions
  9. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 I2C Interface Timing Characteristics
    7. 8.7 Timing Requirements
    8. 8.8 Typical Characteristics
  10. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1  Fixed-Frequency DCS Control Topology
      2. 9.3.2  Forced PWM and Power Save Modes
      3. 9.3.3  Precise Enable
      4. 9.3.4  Start-Up
      5. 9.3.5  Switching Frequency Selection
      6. 9.3.6  Output Voltage Setting
        1. 9.3.6.1 Output Voltage Range
        2. 9.3.6.2 Output Voltage Setpoint
        3. 9.3.6.3 Non-Default Output Voltage Setpoint
        4. 9.3.6.4 Dynamic Voltage Scaling
      7. 9.3.7  Compensation (COMP)
      8. 9.3.8  Mode Selection and Clock Synchronization (MODE/SYNC)
      9. 9.3.9  Spread Spectrum Clocking (SSC)
      10. 9.3.10 Output Discharge
      11. 9.3.11 Undervoltage Lockout (UVLO)
      12. 9.3.12 Overvoltage Lockout (OVLO)
      13. 9.3.13 Overcurrent Protection
        1. 9.3.13.1 Cycle-by-Cycle Current Limiting
        2. 9.3.13.2 Hiccup Mode
        3. 9.3.13.3 Current Limit Mode
      14. 9.3.14 Power Good (PG)
        1. 9.3.14.1 Standalone or Primary Device Behavior
        2. 9.3.14.2 Secondary Device Behavior
      15. 9.3.15 Remote Sense
      16. 9.3.16 Thermal Warning and Shutdown
      17. 9.3.17 Stacked Operation
    4. 9.4 Device Functional Modes
      1. 9.4.1 Power-On Reset
      2. 9.4.2 Undervoltage Lockout
      3. 9.4.3 Standby
      4. 9.4.4 On
    5. 9.5 Programming
      1. 9.5.1 Serial Interface Description
      2. 9.5.2 Standard, Fast, Fast Mode Plus Protocol
      3. 9.5.3 I2C Update Sequence
      4. 9.5.4 I2C Register Reset
    6. 9.6 Register Map
  11. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Selecting the Inductor
        2. 10.2.2.2 Selecting the Input Capacitors
        3. 10.2.2.3 Selecting the Compensation Resistor
        4. 10.2.2.4 Selecting the Output Capacitors
        5. 10.2.2.5 Selecting the Compensation Capacitor, CC
        6. 10.2.2.6 Selecting the Compensation Capacitor, CC2
      3. 10.2.3 Application Curves
    3. 10.3 Best Design Practices
    4. 10.4 Power Supply Recommendations
    5. 10.5 Layout
      1. 10.5.1 Layout Guidelines
      2. 10.5.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 第三方产品免责声明
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 接收文档更新通知
    4. 11.4 支持资源
    5. 11.5 Trademarks
    6. 11.6 静电放电警告
    7. 11.7 术语表
  13. 12Mechanical, Packaging, and Orderable Information

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机械数据 (封装 | 引脚)
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订购信息

10.2.2.2 Selecting the Input Capacitors

As with all buck converters, the input current of the TPS6287x-Q1 devices is discontinuous. The input capacitors provide a low-impedance energy source for the device, and their value, type, and location are critical for correct operation. TI recommends low-ESR multilayer ceramic capacitors for best performance. In practice, the total input capacitance is typically comprised of a combination of different capacitors, in which larger capacitors provide the decoupling at lower frequencies and smaller capacitors provide the decoupling at higher frequencies.

The TPS6287x-Q1 devices feature a butterfly layout with two pairs of VIN and GND pins on opposite sides of the package. This allows the input capacitors to be placed symmetrically on the PCB so that the electromagnetic fields generated cancel each other out, thereby reducing EMI.

The duty cycle of the converter is given by:

Equation 7. D=VOUTη×VIN

where

  • VIN is the input voltage.
  • VOUT is the output voltage.
  • η is the efficiency.

Equation 8. D=0.750.9×3.3=0.253

The value of input capacitance needed to meet the input voltage ripple requirements is given by:

Equation 9. CIN=D×(1-D)×IOUTVIN(PP)×fsw

where

  • D is the duty cycle.
  • fsw is the switching frequency.
  • L is the inductance.
  • IOUT is the output current.
100mV is used as the input voltage ripple target.

Equation 10. CIN=0.253×1-0.253×11.30.1×2.25×106=9.5 μF

The value of CIN calculated with Equation 9 is the effective capacitance after all derating, tolerance, and aging effects have been considered. 5 µF effective capacitance per input pin is required. TI recommends multilayer ceramic capacitors with an X7R dielectric (or similar) for CIN, and these capacitors must be placed as close to the VIN and GND pins as possible to minimize the loop area.

Table 10-4 lists a number of capacitors suitable for this application. This list is not exhaustive and other capacitors from other manufacturers can also be suitable.
Table 10-3 List of Recommended Input Capacitors
Capacitance DimensionsVoltage RatingManufacturer, Part Number(1)
mm (Inch)
470 nF ±10%1005 (0402)10 VMurata, GCM155C71A474KE36D
470 nF ±10%1005 (0402)10 VTDK, CGA2B3X7S1A474K050BB
10 μF ±10%2012 (0805)10 VMurata, GCM21BR71A106KE22L
10 μF ±10%2012 (0805)10 VTDK, CGA4J3X7S1A106K125AB
22 μF ±10%3216 (1206)10 VMurata, GCM31CR71A226KE02L
22 μF ±20%3216 (1206)10 VTDK, CGA5L1X7S1A226M160AC