I'm designing a BoosterPack to evaluate GaN devices with the help of a microcontroller.            

This post documents the PCB layout, specific for significant currency and high switching frequency.

 

The GaN Evaluation BoosterPack - Computer Controlled version of the Reference Design

The GaN BoosterPack that I'm designing is a close brother to TI's LMG5200 reference design. The power electronics part is - deliberate - identical to the reference.

The purpose of the circuit is to have an evaluation tool where you can check GaN FET behaviour under varying conditions.

So I left all GaN power related parts as-is, and replaced the input control logic.

The reference design uses RC circuits to generate the required input signals. The user controls frequency and duty cycle of that input circuit by providing an external PWM signal.

Other parameters, such as the deadband and the duty cycle ratio between different driver signals are preset.  You can change them by modifying the discrete components on the reference design (read: desoldering and replacing SMD caps and/or resistors).

 

I'm modding the design so that it takes the deadband from an external source. In my case, that source is a Hercules LaunchPad that runs an SCPI interpreter and can be controlled by LabVIEW.

 

The Gerbers for the reference designs are available from TI's website. If you load all the Gerber files into KiCAD's Gerber viewer, here are the ones you have to activate to get a good look-and-feel of the design:

  • 1 midlayer 1  G1 (upper midlayer)
  • 2 bottom layer GBL
  • 6 drill layer GD1
  • 7 drill guideline GG1
  • 23 interpanel GP1 (lower midlayer)
  • 26 top layer GTL
  • 3 bottom overlay GBO
  • 27 top overlay GTO

 

{gallery} TI Reference Design

Upper Mid Layer

1 midlayer 1  G1 (upper midlayer)

2 bottom layer GBL

2 bottom layer GBL

interpanel GP1 (lower midlayer)

23 interpanel GP1 (lower midlayer)

top layer GTL

26 top layer GTL

drill layer GD1

6 drill layer GD1

drill guideline GG1

7 drill guideline GG1

bottom overlay GBO

3 bottom overlay GBO

top overlay GTO

27 top overlay GTO

Layer Stack Up

 

 

The Layout Application Note

TI has an elaborate  guide with 'Layout Considerations for LMG5200 GaN Power Stage'. This document contains theory and practice on how to layout 2 or 4 layer PCBs for this device.

This goes well together with the EVM kit that I'm copy-catting here. The PCB of the EVM is used as the practical realisation of the layout theories and guidelines.

That means that I have all that's needed for my work: explanation, a physical example (TI gave me an EVM) and the Gerber files. Over to KiCad and draw my own version...

 

 

 

In the next post I'll post the schematics and PCB layout - and the KiCAD sources.

(was planning to do that now, but I can't upload images to the blog since this afternoon...)

 

Related Blogs
Hercules LaunchPad and GaN FETs - Part 1: Control Big Power with a Flimsy Mouse Scroll Wheel
Hercules LaunchPad and GaN FETs - Part 2: Make a BoosterPack
Hercules LaunchPad and GaN FETs - Part 3a: BoosterPack Layout - Reference Design
Hercules LaunchPad and GaN FETs - Part 3b: BoosterPack Layout - my version
Hercules LaunchPad and GaN FETs - Side Note A: BoosterPack Layout - Custom KiCad Parts
Hercules LaunchPad and GaN FETs - Side Note B: Look at the PCB
Rotary Encoders - Part 1: Electronics
Checking Out GaN Half-Bridge Power Stage: Texas Instruments LMG5200 - Part 1: Preview
Rotary Encoders - Part 4: Capturing Input on a Texas Instruments Hercules LaunchPad with eQEP
Vintage Turntable repair: Can I fix a Perpetuum Ebner from 1958 - part 4 - Hercules LaunchPad Enhanced PWM try-out