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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 (smile)

  • 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

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