SLVSH72B December   2023  – October 2026 TPS281C100

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Options
  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 SNS Timing Characteristics
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  8. 7 Parameter Measurement Information
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Device Functional Modes
    4. 8.4 Working Mode
    5. 8.5 Feature Description
      1. 8.5.1 Accurate Current Sense
        1. 8.5.1.1 High Accuracy Sense Mode
      2. 8.5.2 Programmable Current Limit
        1. 8.5.2.1 Short-Circuit and Overload Protection
        2. 8.5.2.2 Capacitive Charging
      3. 8.5.3 Inductive-Load Switching-Off Clamp
      4. 8.5.4 Inductive Load Demagnetization
      5. 8.5.5 Full Protections and Diagnostics
        1. 8.5.5.1 Open-Load Detection
        2. 8.5.5.2 Thermal Protection Behavior
        3. 8.5.5.3 Undervoltage Lockout (UVLO) Protection
        4. 8.5.5.4 Reverse Polarity Protection
          1. 8.5.5.4.1 Method 1
          2. 8.5.5.4.2 Method 2 (GND Network Protection)
        5. 8.5.5.5 Protection for MCU I/Os
        6. 8.5.5.6 Diagnostic Enable Function
        7. 8.5.5.7 Loss of Ground
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
        1. 9.2.1.1 IEC 61000-4-4 EFT
        2. 9.2.1.2 IEC 61000-4-5 Surge
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Selecting RILIM
        2. 9.2.2.2 Selecting RSNS
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
        1. 9.4.1.1 EMC Considerations
      2. 9.4.2 Layout Example
        1. 9.4.2.1 DNT Layout Without a GND Network
      3. 9.4.3 Thermal Considerations
  11. 10Device and Documentation Support
    1. 10.1 Receiving Notification of Documentation Updates
    2. 10.2 Support Resources
    3. 10.3 Trademarks
    4. 10.4 Electrostatic Discharge Caution
    5. 10.5 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

9.2.2.2 Selecting RSNS

Table 9-1 shows the requirements for the load current sense in this application. The KSNS value is specified for the device and can be found in Section 6.

Table 9-1 RSNS Calculation Parameters
PARAMETEREXAMPLE VALUE
Current Sense Ratio (KSNS1)

800

Current Sense Ratio (KSNS2)

24

Largest diagnosable load current

3A

Smallest diagnosable load current

4mA

Full-scale ADC voltage5.0V
ADC resolution10 bit

The load current measurement up to 3A confirms 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 4mA allows for accurate measurement of low load currents and enable the distinction open load faults from supported nominal load currents. For load currents < 50mA, 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 Section 8.5.1 for more information.

The RSNS resistor value must 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 must confirm 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 1.0kΩ sense resistor satisfies both requirements.

Table 9-2 VSNS Calculation
Sense Mode

OL_ON

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

Standard Sensing

LO

3A

800

3.75

1000

3.75

75%

High Accuracy Sensing

HI

0.004A

24

0.166

1000

0.1663.3% (≅34LSBs)