ZHCSO18A december   2022  – june 2023 TPS281C30

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  5. 4 Revision History
  6. 5 Device Comparison Table
  7. 6 Pin Configuration and Functions
  8. 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 Thermal Information
    6. 7.6 Electrical Characteristics
    7. 7.7 SNS Timing Characteristics
    8. 7.8 Switching Characteristics
    9. 7.9 Typical Characteristics
  9. 8 Parameter Measurement Information
  10. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Device Functional Modes
      1. 9.3.1 Working Mode
    4. 9.4 Feature Description
      1. 9.4.1 Accurate Current Sense
        1. 9.4.1.1 High Accuracy Sense Mode
      2. 9.4.2 Programmable Current Limit
        1. 9.4.2.1 Short-Circuit and Overload Protection
        2. 9.4.2.2 Capacitive Charging
      3. 9.4.3 Inductive-Load Switching-Off Clamp
      4. 9.4.4 Inductive Load Demagnetization
      5. 9.4.5 Full Protections and Diagnostics
        1. 9.4.5.1 Open-Load Detection
        2. 9.4.5.2 Thermal Protection Behavior
        3. 9.4.5.3 Undervoltage Lockout (UVLO) Protection
        4. 9.4.5.4 Overvoltage (OVP) Protection
        5. 9.4.5.5 Reverse Polarity Protection
        6. 9.4.5.6 Protection for MCU I/Os
        7. 9.4.5.7 Diagnostic Enable Function
        8. 9.4.5.8 Loss of Ground
  11. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
        1. 10.2.1.1 IEC 61000-4-5 Surge
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Selecting RILIM
        2. 10.2.2.2 Selecting RSNS
    3. 10.3 Power Supply Recommendations
    4. 10.4 Layout
      1. 10.4.1 Layout Guidelines
        1. 10.4.1.1 EMC Considerations
      2. 10.4.2 Layout Example
        1. 10.4.2.1 PWP Layout without a GND Network
        2. 10.4.2.2 PWP Layout with a GND Network
        3. 10.4.2.3 RGW Layout with a GND Network
      3. 10.4.3 Thermal Considerations
  12. 11Device and Documentation Support
    1. 11.1 接收文档更新通知
    2. 11.2 支持资源
    3. 11.3 Trademarks
    4. 11.4 静电放电警告
    5. 11.5 术语表
  13. 12Mechanical, Packaging, and Orderable Information

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10.2.2.2 Selecting RSNS

Table 10-1 shows the requirements for the load current sense in this application. The KSNS value is specified for the device and can be found in the Specifications section.

Table 10-1 RSNS Calculation Parameters
PARAMETEREXAMPLE VALUE
Current Sense Ratio (KSNS1)

1300

Current Sense Ratio (KSNS2)

24

Largest diagnosable load current

4.8 A

Smallest diagnosable load current

4 mA

Full-scale ADC voltage5.0 V
ADC resolution10 bit

The load current measurement up to 4.8 A ensures that even in the event of a overload but below the set current limit, the MCU can register and react by turning off the FET while the low level of 4 mA allows for accurate measurement of low load currents and enable the distinction open load faults from supported nominal load currents. For load currents < 50 mA, the customer can enable high accuracy sensing to change the sense ratio from KSNS1 to KSNS2. This prevents the requirement of a higher resolution ADC and it also increases sense accuracy. Go to high accuracy sensing for more information.

The RSNS resistor value should be selected such that the largest diagnosable load current puts the SNS pin voltage (VSNS) at about 90% of the ADC full-scale. With this design, any ADC value above 80% of full scale (FS) can be considered a fault. Additionally, the RSNS resistor value should ensure that the smallest diagnosable load current does not cause VSNS to fall below at a least a few LSB of the ADC.

With the given example values, a 1.0-kΩ sense resistor satisfies both requirements.

Table 10-2 VSNS Calculation
Sense Mode

OL_ON

LOAD (A)SENSE RATIOISNS (mA)RSNS (Ω)VSNS (V)% of 5-V ADC

Standard Sensing

LO

4.8A

1200

3.69

1000

3.69

73.8%

High Accuracy Sensing

HI

0.004

24

0.166

1000

0.1663.3% (~34 LSBs)