SNVAA32 july   2023 LMQ644A2-Q1

 

  1.   1
  2.   LMQ644A2-Q1 6-Phase Buck Regulator Design for Automotive ADAS Applications
  3.   Trademarks
  4. 1 Introduction
    1. 1.1 Features and Electrical Performance
  5. 2Design Specifications
  6. 3Application Circuit Diagram and Operating Configuration Table
  7. 4Top and Bottom Board Views
  8. 5Test Data and Performance Curves
    1. 5.1 Conversion Efficiency
    2. 5.2 Operating Waveforms
      1. 5.2.1 6-phase Switching
      2. 5.2.2 Load Transient Response
      3. 5.2.3 Loop Response
      4. 5.2.4 Startup/Shutdown
    3. 5.3 Thermal Performance
    4. 5.4 CISPR 25 EMI Performance
  9. 6EVM Documentation
    1. 6.1 Schematic
    2. 6.2 Bill of Materials
    3. 6.3 PCB Layout
  10. 74-Phase Configuration
    1. 7.1 4-Phase Switching
  11. 8Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
    2. 8.2 Documentation Support
      1. 8.2.1 References
        1. 8.2.1.1 PCB Layout Resources
        2. 8.2.1.2 Thermal Design Resources

Abstract

The LMQ644A2-Q1 is a dual channel 36-V synchronous buck DC/DC converter which supports maximum 6 A per channel. The device is stackable up to 6 phases for higher output currents up to 36-A without external clocks. The device uses current-mode control architecture for easy loop compensation, fast transient response, and excellent load and line regulation.

LMQ644xx series also provides 4A channel and 5A channel versions. Please refer Table 1-1 for more information.

Table 1-1 LMQ644xx Series Synchronous Buck DC/DC Converter
Part Number VIN Range Start-up Voltage Maximum IOUT

(Single-phase, dual-output)

 Maximum IOUT

(Dual-phase, single-output)
LMQ64480-Q1 3.0 V to 36 V 3.8 V 4 A 8 A
LMQ644A0-Q1 3.0 V to 36 V 3.8 V 5 A 10 A
LMQ644A2-Q1 3.0 V to 36 V 3.8 V 6 A 12 A

The LMQ644A2-Q1 6-phase reference design is a high-density automotive synchronous buck DC/DC regulator that employs synchronous rectification to achieve high conversion efficiency. It requires minimum 3.8 V to start up and works down to 3.0 V after start up. The regulator supports up to 36 A output current, and allows maximum 36 V input for a short time operation. The regulator provides three fixed output voltage options (2.5 V, 3.3 V and 5.0 V). The default configuration is 3.3V when J1 #1 - #2 are short. For 5 V output, short J1 #2 - #3. For 2.5 V output, open J1 and short J7.

The regulator design uses the LMQ644A2-Q1 36-V low IQ dual synchronous buck DC/DC converter, having the following features:

  • Wide input voltage range with a dropout mode at low VIN
  • Low shutdown and standby IQ
  • Programmable switching frequency from 100 kHz to 2.2 MHz
  • Integrated low RDSON MOSFETs
  • Selectable spread spectrum modulation
  • Integrated VIN capacitors
  • Cycle-by-cycle current limit with hiccup-mode overload protection

The LMQ644A2-Q1 is available in a 25-pin WQFN package with 5-mm × 4-mm footprint. See the LMQ644A2-Q1 3-V to 36-V, 12-A Low IQ Dual Synchronous Buck DC/DC Converter data sheet for more information.