SNVSAO6C September   2017  – March 2018 LMZM33603

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
    1.     Simplified Schematic
  3. 3 Description
    1.     Safe Operating Area
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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 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. 7 Detailed 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  Feed-Forward Capacitor, CFF
      3. 7.3.3  Output Current vs Output Voltage
      4. 7.3.4  Voltage Dropout
      5. 7.3.5  Switching Frequency (RT)
      6. 7.3.6  Synchronization (SYNC)
      7. 7.3.7  Input Capacitors
      8. 7.3.8  Output Capacitors
      9. 7.3.9  Output On/Off Enable (EN)
      10. 7.3.10 Programmable Undervoltage Lockout (UVLO)
      11. 7.3.11 Power Good (PGOOD)
      12. 7.3.12 Overcurrent Protection (OCP)
      13. 7.3.13 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Active Mode
      2. 7.4.2 Shutdown Mode
  8. 8 Application 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 Feed-Forward 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. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
    3. 10.3 Theta JA vs PCB Area
    4. 10.4 EMI
      1. 10.4.1 EMI Plots
    5. 10.5 Package Specifications
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Custom Design With WEBENCH® Tools
    2. 11.2 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
    1. 12.1 Tape and Reel Information

7.3.1 Adjusting the Output Voltage

A resistor divider connected to the FB pin (pin 16) programs the output voltage of the LMZM33603. The output voltage adjustment range is from 1 V to 18 V. (See Output Current vs Output Voltage for the maximum allowable output voltage as a function of output current.) Figure 18 shows the feedback resistor connections for setting the output voltage. The recommended value of RFBB is 10 kΩ. The value for RFBT can be calculated using Equation 1. Depending on the output voltage, a feed-forward capacitor, CFF, may be required for optimum transient performance. Table 1 lists the standard external RFBT and CFF values for several output voltages between 2.5 V and 18 V. Table 2 lists the values for output voltages below 2.5 V. Additionally, Table 1 and Table 2 include the recommended switching frequency (FSW), the frequency setting resistor (RRT), and the minimum and maximum output capacitance for each of the output voltages listed.

For designs with RFBB other than 10 kΩ, adjust CFF and RFBT such that (CFF × RFBT) is unchanged and adjust RFBT such that (RFBT / RFBB) is unchanged.

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Equation 1. LMZM33603 Rfbt2.gif
LMZM33603 ZZtopCff.gifFigure 18. Setting the Output Voltage

Table 1. Required Component Values (VOUT ≥ 2.5 V)

VOUT (V) RFBT (kΩ)(3) CFF (pF) fSW (kHz) RRT (kΩ) COUT(min) (µF)(1) COUT(max) (µF)(2)
2.5 15.0 220 250 162 150 400
3.3 23.2 150 300 133 88 300
5 40.2 100 450 88.7 66 200
6 49.9 68 550 71.5 54 160
7.5 64.9 47 650 60.4 40 130
9 80.6 47 700 56.2 36 110
12 110 open 900 44.2 22 80
13.5 124 open 1000 39.2 22 75
15 140 open 1100 35.7 20 65
18 169 open 1200 33.2 16 55
(1) For output voltages ≥ 2.5 V, the minimum required output capactiance must be comprised of ceramic type and account for DC bias and temperature derating.
(2) The maximum output capactiance must include the required ceramic COUT(min). Additional capacitance, may be ceramic type, low-ESR polymer type, or a combination of the two.
(3) RFBB = 10.0 kΩ.

Table 2. Required Component Values (VOUT < 2.5 V)

VOUT (V) RFBT (kΩ)(1) CFF (pF) FSW (kHz) RRT (kΩ) COUT
1 to 2.5 see Equation 1 open 250 162 150-µF ceramic +
470-µF polymer
(1) RFBB = 10 kΩ. For VOUT = 1 V, RFBB= open and RFBT = 0 Ω.