SNVSAO4D December   2017  – August 2020 LMZM33602

PRODUCTION DATA  

  1. 1Features
  2. 2Applications
  3. 3Description
  4. 4Revision History
  5. 5Pin Configuration and Functions
    1.     Pin Functions
  6. 6Specifications
    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
    7. 6.7 Typical Characteristics (VIN = 5 V)
    8. 6.8 Typical Characteristics (VIN = 12 V)
    9. 6.9 Typical Characteristics (VIN = 24 V)
  7. 7Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Adjusting the Output Voltage
      2. 7.3.2  Feedforward Capacitor, CFF
      3. 7.3.3  Voltage Dropout
      4. 7.3.4  Switching Frequency (RT)
      5. 7.3.5  Synchronization (SYNC)
      6. 7.3.6  Input Capacitors
      7. 7.3.7  Output Capacitors
      8. 7.3.8  Output On/Off Enable (EN)
      9. 7.3.9  Programmable Undervoltage Lockout (UVLO)
      10. 7.3.10 Power Good (PGOOD)
      11. 7.3.11 Overcurrent Protection (OCP)
      12. 7.3.12 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Active Mode
      2. 7.4.2 Shutdown Mode
  8. 8Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Output Voltage Setpoint
        3. 8.2.2.3 Feedforward Capacitor (CFF)
        4. 8.2.2.4 Setting the Switching Frequency
        5. 8.2.2.5 Input Capacitors
        6. 8.2.2.6 Output Capacitor Selection
        7. 8.2.2.7 Application Curves
  9. 9Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Development Support
        1. 9.1.1.1 Custom Design With WEBENCH® Tools
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary

7.3.3 Voltage Dropout

Voltage dropout is the difference between the input voltage and output voltage that is required to maintain output voltage regulation while providing the rated output current.

To ensure the LMZM33602 maintains output voltage regulation at the recommended switching frequency, over the operating temperature range, the following requirements apply:

For output voltages ≤ 5 V, the minimum VIN is 4 V or (VOUT + 1.5 V), whichever is greater.

For output voltages > 5 V, the minimum VIN is (1.3 × VOUT).

However, if fixed switching frequency operation is not required, the LMZM33602 operates in a frequency foldback mode when the dropout voltage is less than the recommendations above. Frequency foldback reduces the switching frequency to allow the output voltage to maintain regulation as input voltage decreases. Figure 7-2 through Figure 7-7 show typical dropout voltage and frequency foldback curves for 3.3-V, 5-V, and 12-V outputs at TA = 25°C. (Note: As ambient temperature increases, dropout voltage and frequency foldback occur at higher input voltage.)

GUID-187EFABC-95C7-42E0-81C2-35D0F2174992-low.gif
VOUT = 3.3 V fSW = 300 kHz
Figure 7-2 Voltage Dropout
GUID-3CDFE6B2-132A-4747-A87F-367AC2BBCAF2-low.gif
VOUT = 5 V fSW = 450 kHz
Figure 7-4 Voltage Dropout
GUID-A7E4DF0B-D10D-4F10-82CC-DC0045E021F9-low.gif
VOUT = 12 V fSW = 900 kHz
Figure 7-6 Voltage Dropout
GUID-9B7778C9-B543-46AF-BCD2-58DF7A7B3B08-low.gif
VOUT = 3.3 V fSW = 300 kHz
Figure 7-3 Frequency Foldback
GUID-CD53F632-8703-4C0C-B55A-D1BB9410E939-low.gif
VOUT = 5 V fSW = 450 kHz
Figure 7-5 Frequency Foldback
GUID-7D1FBBA1-AF7A-40F7-97AD-9345B757B412-low.gif
VOUT = 12 V fSW = 900 kHz
Figure 7-7 Frequency Foldback