Weekly Summary - Robert Tang

Owned by Kevin Li
Last updated: yesterday at 20:37 by Robert Tang
2 min read

Introduction

Brief documentation of what Robert Tang has been up to each week to help in synthesis of final report and so @Kevin Li can visualize where the time is going and help resolve roadblocks. Formatting is expected to be similar to Weekly Summary - Meghan Dang.

Table of Contents

Related Resources

Weeks

Week 1

  • Started and completed the Electrical Bootcamp

    • Carried out component selections, selecting resistors, capacitors, diodes, LDO IC to make a LDO regulator that converts 12 Volt to 5 Volt

      • Created footprints for the LDO IC and LED, and created schematics and PCB layouts

    • Applied methods such as polygon pouring, carefully selecting via placement to maximize the efficiency and effectiveness of the 4 layer PCB board created

  • Researching about linear regulator and started looking into the project beginning next week (Week 2), which is buck converter.

Week 2

  • Started the project (24V to 5V at 5A buck converter)

    • Learnt about how a buck converter work, and more details into buck converters, such as CCM, asynchronous and synchronous buck converters.

    • Started selecting components for the buck converters

      • Selected buck converter IC (MPS)

      • Selected input capacitor

      • In the process of selecting an inductor, looking at inductor values between 4.7uH to 6.8uH

  • Started designing schematics

    • Imported WARG template, and power ports connection

    • Created footprint and symbol for buck converter IC

    • Placed the input capacitor (from WARG library)

Week 3

  • Finished the schematics, the schematics is sent to Meghan and Kevin for review

    • Buck converter part:

      • Implemented input and output capacitor network (carried out calculation and selected components from the library)

      • Feedback voltage network implemented (0.5V V_FB)

      • Added all other components

    • Reverse Polarity protection

      • Research different methods of RPP

        • Diode, high side PMOS, low side NMOS, Driver IC and high side MOSFET

      • Selected a Driver IC (LM74700QDBVRQ1) and according to the datasheet selected the NMOSFET

        • Created symbols and footprint for the IC

      • Implemented the circuit in the schematics

    • Adjust the finished schematics based on comments

  • Started doing the layout, and getting the necessary formats of the PCB board

    • Imported the layer stackup and design rules

Week 4

  • Updated schematics

    • Added comments to the schematics

    • Changed components

      • LED circuit: 390R to 1kR for a smaller current

      • Added 2*10uF caps and 0.1uF caps for better filtering at the RPP circuit

      • Modified NMOS symbol

  • Started and finished placement

    • Placed the components, carefully considering the signal integrity

    • Detailed comments can be found in the 24V-5V design document

  • Started routing

Week 5

  • Updated placements:

    • Update the connector to the correct one

      • The new connector is huge to compensate for that I shifted most components to the left a bit

    • Fixed small footprint issues

  • Almost finished routing

    • Connected V_BAT, V_BAT_PROC, 5V0 rails with big polygons

    • Doing a 4-layer PCB (signal/power+GND+GND+signal/power)

      • For 5V0, route to L4 first and then up to L1

    • Changing the thermal relief for certain pads

    • Placed GND stitching and GND pour on L1 and L4

    • The other routing details can be seen in the PCB doc and the design doc

Week 6

  • Chill week

  • Fixed small issues on the PCB to make the board looks good

  • Tried to start a PDN analysis

    • Need to account for:

      • VBUS: Input connector -> NMOS, NMOS -> Buck IC

      • SW: Buck IC -> Inductor

      • 5V: Inductor -> Pixhawk Conn, Inductor -> USB-C Conn, also do Inductor to farthest decoupling cap down (basically before the via punch down to L4).

  • Started looking at the next project

    • Pre-charge circuit

Week 7

  • 24V to 5V @ 5A Buck Converter

    • Adjusted layout for better appearance

    • PDN analysis:

      • Encountered some issues, finally calculate the impedance by voltage drop over the current

      • The screenshots are updated in the design document

  • 12s Pre-charge Circuit

    • Defined system block diagram

    • Researched about what pre-charge circuit, CAN interface, and current/voltage sense

    • Looked at options for pre-charge IC, currently reading the TPS48111 IC

Week 8

  • Buck:

    • Components and layout reviewed

    • Added bottom layer silkscreen and exported the Gerber file for fab

    • Verified selected Pixhawk connector’s compatibility with the harness

  • LED Board harness (helped work session)

  • Board review (6s to 5V buck)

  • 12S Pre-charge

    • Looked at the TPS chip thoroughly for understanding how it work

    • Looking for more options for the pre-charge ic

    • Implement the STM32 MCU and the CAN circuit for the CAN adapter board

Week 9

  • 24V to 5V Buck:

    • Added bottom layer meme

    • Export Gerber files and have it verified

    • Add to order in JLCPCB (midterm order)

  • 12S Pre-charge:

    • Selected pre-charge IC (TPS48111 chip)

      • Implemented symbols and footprints

    • High level system architecture defined

    • Started looking at options for powering the STM32 (12S to BUCK to LDO to 3.3V)