SLVSH48A May   2024  – September 2024 TPS7H1121-SP

PRODMIX  

  1.   1
  2. Features
  3. Applications
  4. Description
  5. Device Options
  6. Pin Configuration and Functions
  7. 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 Quality Conformance Inspections
    7. 6.7 Typical Characteristics
  8. Parameter Measurement Information
  9. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Adjustable Output Voltage (Feedback Circuit)
      2. 8.3.2  Enable
      3. 8.3.3  Dropout Voltage VDO
      4. 8.3.4  Output Voltage Accuracy
      5. 8.3.5  Output Noise
      6. 8.3.6  Power Supply Rejection Ratio (PSRR)
      7. 8.3.7  Soft Start
      8. 8.3.8  Power Good (PG)
      9. 8.3.9  Stability
        1. 8.3.9.1 Stability
        2. 8.3.9.2 STAB Pin
      10. 8.3.10 Programmable Current Limit
      11. 8.3.11 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Enable / Disable
  10. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Output Voltage Configuration
        2. 9.2.2.2 Output Voltage Accuracy
        3. 9.2.2.3 Enable Threshold
        4. 9.2.2.4 Soft Start Capacitor
        5. 9.2.2.5 Programmable Current Limit Resistor
        6. 9.2.2.6 Characterization of Overcurrent Events that Exceed Thermal Limits
        7. 9.2.2.7 Power Good Pull Up Resistor
        8. 9.2.2.8 Capacitors
          1. 9.2.2.8.1 Hybrid Output Capacitor Network
        9. 9.2.2.9 Frequency Compensation
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Third-Party Products Disclaimer
    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

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発注情報

Programmable Current Limit

Brick-wall current limit, also known as constant current limit, is shown in Figure 8-3. In this mode, once IPCL is reached and the current limit circuitry has time to respond, the TPS7H1121 LDO enters constant current regulation mode. In other words, the output voltage reduces to whatever value is needed to keep the output current at ILIM. Once the fault is removed the device resumes regulation.

Due to the high power dissipation in brick-wall current limit, there is the possibility that the TPS7H1121 enters thermal shutdown which causes the device to stop regulation until the TPS7H1121 cools enough to exit thermal shutdown.

TPS7H1121-SP Simplified Brick-Wall Current
                    Limit Waveforms Figure 8-3 Simplified Brick-Wall Current Limit Waveforms

The programmable current limit's accuracy tightens with increased load current; Table 8-1 shows the recommended E96 value with a typical accuracy.

With the stipulated accuracy of the current limit, the programmable current limit resistor RCL needs to be selected to accommodate the negative portion of the accuracy current limit circuitry. Additionally, a 20% headroom margin is recommended to prevent the current limit from intervening during nominal operation. For example an application with a nominal load of 1A can have a minimum programmable current limit setting of 1.4A / 97.6kΩ; the setting for a 97.6kΩ programmable current limit has a negative accuracy of -25% which leads a minimum intervening current limit of 1.05A.

For example an application with a nominal load of 1A is recommended to have a minimum intervening current of 1.2A; which yields a nominal current limit of 1.6A. Therefore an RCL setting of 80.6kΩ with a negative accuracy of -25% leads to a minimum intervening current limit of 1.2A; which complies with the recommended 20% headroom.

Table 8-1 Recommended Current Limit Setting Resistor
PROGRAMMABLE CURRENT LIMIT SETTING (A) E96 (kΩ) ACCURACY
0.32 442 ±35%
0.4 392
0.5 332
0.6 267 ±30%
0.7 205
0.75 174
0.8 169
0.9 158
1 143
1.1 133 ±25%
1.2 121
1.3 110
1.4 97.6
1.5 88.7
1.55 82.5
1.6 80.6
1.7 78.6
1.8 75
1.9 71.5
2 69.8
2.1 66.5 ±20%
2.2 63.4
2.3 60.4
2.4 57.6
2.5 54.9
2.6 52.3
2.7 49.9
2.8 46.4
2.9 44.2
3 41.2