SNOSD37B march   2017  – april 2023 LMG1205

PRODUCTION DATA  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  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
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Input and Output
      2. 7.3.2 Start-up and UVLO
      3. 7.3.3 HS Negative Voltage and Bootstrap Supply Voltage Clamping
      4. 7.3.4 Level Shift
    4. 7.4 Device Functional Modes
  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 VDD Bypass Capacitor
        2. 8.2.2.2 Bootstrap Capacitor
        3. 8.2.2.3 Power Dissipation
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
      1.      Mechanical, Packaging, and Orderable Information

Package Options

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

Layout Guidelines

Small gate capacitance and Miller capacitance enable enhancement mode GaN FETs to operate with fast switching speed. The induced high dv/dt and di/dt, coupled with a low gate threshold voltage and limited headroom of enhancement mode GaN FETs gate voltage, make the circuit layout crucial to the optimum performance. Following are some recommendations:

  1. The first priority in designing the layout of the driver is to confine the high peak currents that charge and discharge the GaN FETs gate into a minimal physical area. This decreases the loop inductance and minimize noise issues on the gate terminal of the GaN FETs. The GaN FETs must be placed close to the driver.
  2. The second high current path includes the bootstrap capacitor, the local ground referenced VDD bypass capacitor and low-side GaN FET. The bootstrap capacitor is recharged on a cycle-by-cycle basis through the bootstrap diode from the ground referenced VDD capacitor. The recharging occurs in a short time interval and involves high peak current. Minimizing this loop length and area on the circuit board is important to ensure reliable operation.
  3. The parasitic inductance in series with the source of the high-side FET and the low-side FET can impose excessive negative voltage transients on the driver. TI recommends connecting the HS pin and VSS pin to the respective source of the high-side and low-side transistors with a short and low-inductance path.
  4. The parasitic source inductance, along with the gate capacitor and the driver pull-down path, can form an LCR resonant tank, resulting in gate voltage oscillations. An optional resistor or ferrite bead can be used to damp the ringing.
  5. Low ESR/ESL capacitors must be connected close to the IC, between VDD and VSS pins and between the HB and HS pins to support the high peak current being drawn from VDD during turnon of the FETs. Keeping bullet #1 (minimized GaN FETs gate driver loop) as the first priority, it is also desirable to place the VDD decoupling capacitor and the HB to HS bootstrap capacitor on the same side of the PC board as the driver. The inductance of vias can impose excessive ringing on the IC pins.
  6. To prevent excessive ringing on the input power bus, good decoupling practices are required by placing low-ESR ceramic capacitors adjacent to the GaN FETs.

Figure 10-1 and Figure 10-2 show recommended layout patterns for the LMG1205. Two cases are considered: (1) without any gate resistors, and (2) with an optional turnon gate resistor. Note that 0402 surface mount package is assumed for the passive components in the drawings. For information on DSBGA package assembly, refer to Section 11.2.1.