SNVSC42 September   2023 LMQ644A2-Q1

PRODMIX  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Device Comparison Table
  7. 6 Pin Configuration and Functions
    1. 6.1 Wettable Flanks
  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 Electrical Characteristics
    6. 7.6 Typical Characteristics
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Input Voltage Range (VIN)
      2. 8.3.2  Enable EN Pin and Use as VIN UVLO
      3. 8.3.3  Output Voltage Selection and Soft Start
      4. 8.3.4  SYNC Allows Clock Synchronization and Mode Selection
      5. 8.3.5  Clock Locking
      6. 8.3.6  Adjustable Switching Frequency
      7. 8.3.7  Power-Good Output Voltage Monitoring
      8. 8.3.8  Internal LDO, VCC UVLO, and BIAS Input
      9. 8.3.9  Bootstrap Voltage and VCBOOT-UVLO (CB1 and CB2 Pin)
      10. 8.3.10 CONFIG Device Configuration Pin
      11. 8.3.11 Spread Spectrum
      12. 8.3.12 Soft Start and Recovery From Dropout
      13. 8.3.13 Overcurrent and Short-Circuit Protection
      14. 8.3.14 Hiccup
      15. 8.3.15 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Standby Mode
      3. 8.4.3 Active Mode
        1. 8.4.3.1 Peak Current Mode Operation
        2. 8.4.3.2 Auto Mode Operation
          1. 8.4.3.2.1 Diode Emulation
        3. 8.4.3.3 FPWM Mode Operation
        4. 8.4.3.4 Minimum On-time (High Input Voltage) Operation
        5. 8.4.3.5 Dropout
        6. 8.4.3.6 Recovery from Dropout
        7. 8.4.3.7 Other Fault Modes
  10. 9 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  Choosing the Switching Frequency
        2. 9.2.2.2  Setting the Output Voltage
        3. 9.2.2.3  Inductor Selection
        4. 9.2.2.4  Output Capacitor Selection
        5. 9.2.2.5  Input Capacitor Selection
        6. 9.2.2.6  BOOT Capacitor
        7. 9.2.2.7  VCC
        8. 9.2.2.8  CFF and RFF Selection
        9. 9.2.2.9  SYNCHRONIZATION AND MODE
        10. 9.2.2.10 External UVLO
        11. 9.2.2.11 Typical Thermal Performance
      3. 9.2.3 Application Curves
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
        1. 9.4.1.1 Ground and Thermal Considerations
      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 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Glossary
    6. 10.6 Electrostatic Discharge Caution
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.3.10 CONFIG Device Configuration Pin

Several features are included to simplify compliance with CISPR 25 and automotive EMI requirements. To reduce input capacitor ripple current and EMI filter size, the device can be configured to operate in a stack of either two, four, or six phases with corresponding phase shift interleave operation based on the number of phases. For example, in a 4-phase setup, a 90° out-of-phase clock output setup works well for cascaded, multi-channel, or multi-phase power stages. Resistor-adjustable switching frequency as high as 2.2 MHz can be synchronized to an external clock source to eliminate beat frequencies in noise-sensitive applications. Optional spread spectrum modulation further improves the EMI signature.

The CONFIG terminal is used to set up the device for either dual output or single output multi-phase operation. The spread spectrum can also be turned on and off with different resistor values.

Table 8-3 RCONFIG Resistor Selection

RCONFIG (kΩ)

Mode

Spread Spectrum

0

Dual output

No

9.53

2 phase primary

No

19.1

4 phase primary

 No

29.4

6 phase primary

 No

41.2

Secondary

N/A

56.2

2 phase primary

Yes

73.2

4 phase primary

Yes

93.1

6 phase primary

Yes

121

Dual output

Yes

When configured in single output multi-phase operation, the VOSNS2 pin becomes the output of the error amplifier (COMP) and a resistor and capacitor are needed at this pin to compensate the control loop. RC = 11 kOhms, CC = 2.2 nF can be used in initial evaluation for many designs. Increasing the resistance results in higher loop gain and tends to require proportionately larger output capacitors. Decreasing the capacitance increases the loop response of the device, resulting in faster transients but can lower phase margin at the cross-over frequency and can require adjustments to the output capacitance. The table below has several settings for different output configurations.

Table 8-4 Typical Bill of Materials
MODE VOUT1 VOUT2 FREQUENCY COUT EACH PHASE CIN + CHF EACH PHASE L1, L2 RC CC
DUAL 3.3 V 5 V 400 kHz 47 + 22 µF 2 × 10 µF + 1 × 100 nF 3.3 µH INTERNAL INTERNAL
DUAL 3.3 V 5 V 2200 kHz 47 + 22 µF 1 × 10 µF + 1 × 100 nF 0.68 µH INTERNAL INTERNAL
SINGLE 3.3 V 3.3 V 400 kHz 47 + 22 µF 2 × 10 µF + 1 × 100 nF 3.3 µH 11 kΩ 2.2 nF
SINGLE 5 V 5 V 2200 kHz 47 + 22 µF 1 × 10 µF + 1 × 100 nF 1 µH 11 kΩ 2.2 nF
GUID-44D3899D-C3A9-49FB-9BB4-98835F6FE001-low.svg High-Efficiency, Single Output 2-Phase Step-Down Converter
GUID-D7F2F8E4-26E5-4CE1-A031-844F2F5B60CB-low.svg High-Efficiency, Single Output 4-Phase Step-Down Converter
GUID-9D5D988A-A27F-4863-BE53-2D53422E1383-low.svg High-Efficiency, Single Output 6-Phase Step-Down Converter