Power Distribution Board (PDB) - Unarchived

Introduction

Engineer(s):

@Andrew Chai PM, Design Architecture, SMPS

@Kenny Na Sensing + Interface, Design Architecture

@Megan Lee Sensing + Interface, SMPS

@Santosh Erathasari OCP/Short-Circuit Protection, SMPS

Background:

Unarchived project from the 2024 PDB 12S PDB

A power distribution board (PDB) is used for supplying and distributing power form the main power supply to various circuits and subsystems. In a drone/UAV context, the PDB is responsible for converting and distributing the battery pack voltage to the several electronics on the drone itself.

Reference COTS PDBs:

PDB500[X] ← this is the one being used on Big Quad 2025

https://holybro.com/products/pm03d-power-module?pr_prod_strat=e5_desc&pr_rec_id=eefeb6967&pr_rec_pid=7192462491837&pr_ref_pid=7408912400573&pr_seq=uniform

https://holybro.com/products/pixhawk-4-power-module-pm07?pr_prod_strat=e5_desc&pr_rec_id=096753d49&pr_rec_pid=7150469939389&pr_ref_pid=7192462491837&pr_seq=uniform

What:

• Handle 12S input range (40V-50V)

• 12V & 5V output rails with sufficient current output for downstream electronics

  • Common voltage rails

  • Standard connector

• Reverse Polarity Protection (RPP)

• Short Circuit Protection??

• Voltage + Current Sense → maybe need CAN adapter circuit??

  • high current passthrough (may be difficult if this is taking in the entire bus current)

  • might be nice to have a discrete implementation of this, as well as I-sense for each rail

  • Sensing IC without shunt resistor

• Redundancy Support (having just one supply rail makes the system single fault susceptible)

  • Not deemed as important

• Proper input + output filtering networks (need to avoid resonant frequency of Li-Po batteries)

• High efficiency power conversion system

  • Can try playing around with different ways to optimize for efficiency ie soft switching, IC selection

Block Diagram

System Requirements

Pegasus 2 Current Analysis

• Power Budget^^

• 12V @ 3-4A

• 5V @ 4A @Megan Lee

• 3V3 @ 1-2A @Santosh Erathasari

• 3V3_analog LDO <1A

• Nice to have short circuit protection on LV rails

Switch Mode Power Supply

Buck Converter ICs

Andrew, Santosh, Megan

Component	Specifications

Component	Specifications
Open https://www.digikey.ca/en/products/detail/texas-instruments/TPS54360BDDAR/10434703	Vin: 4.5V - 60V Vout: 0.8V - 0.92 X Vin Iout: 3.5A continuous Switching Frequency: 100 kHz - 2 MHz adjustable Efficiency: ~ 91% @ 48V Unit Price: $4.32 ($3.01 for >25 order quantity) Enable Pin ✅
Open https://www.digikey.ca/en/products/detail/vishay-siliconix/SIC463ED-T1-GE3/7616336	Vin: 4.5V - 60V Vout: 0.8V - 0.92 X Vin Iout: 4A continuous Switching Frequency: 100 kHz - 2 MHz adjustable Efficiency: ~ 91% @ 48V Unit Price: $3.28 TR, $6.10 CT Enable Pin ✅
Open https://www.digikey.ca/en/products/detail/analog-devices-inc-maxim-integrated/MAX17576ATG-T/11485132	Vin: 4.5V - 60V Vout: 4.75V - 5.25V Iout: 4A Switching Frequency: 100 kHz, 500kHz, 2.2MHz adjustable Efficiency: ~ 87% @ 40-50V Unit Price: $5.98 TR, $13.81 CT Enable Pin ✅
Open https://www.digikey.ca/en/products/detail/texas-instruments/TPS54560DDAR/3929556	Vin: 4.5V - 60V Vout: 0.8V - 58.8V Iout: 5A Switching Frequency: 100 kHz - 2.5 MHz adjustable Efficiency: ~ 84% @ 48V Unit Price: $4.46 TR, $8.04 CT Enable Pin ✅
Open https://jlcpcb.com/partdetail/RichtekTech-RT6365GSP/C3024482	Vin: 4.5V - 60V Vout: 0.8V - VIN Iout: 5A Switching Frequency: 100 kHz - 2.5 MHz adjustable Efficiency: ~ 84% @ 48V Unit Price: $1.065 Enable Pin ✅
Open https://jlcpcb.com/partdetail/TexasInstruments-TPS54360BDDAR/C524806	Vin: 4.5V - 60V Vout: 0.8V - 58.8V Iout: 3.5A Switching Frequency: 100 kHz - 2.5 MHz adjustable Efficiency: ~ 82% @ 48V Unit Price: $0.84 Enable Pin ✅

Since we likely won’t need > 3A on some of the rails, a 3.5A output current should be sufficient. TPS54360BDDAR has an adjustable switching frequency that goes up to 2MHz so we can make our design pretty compact. It also has a simpler application circuit..?

Inductor Selection

Tbd

Input Capacitance

Tbd

Output Capacitance

Tbd

Reverse Polarity Protection (RPP)

Santosh

Current + Voltage Sense

@Kenny Na, @Megan Lee

Our PDB does not offer battery passthrough to the ESCs, so a typical full load scenario on the PDB may call for over 10A being delivered at 12S potential (~44V nominal, pretty much 48V). At this voltage and current, a shunt resistor-based sensing configuration may cause enough power loss to be something to consider. We can look into passive options for sensing, including using magnetic Hall effect sensors.

Hall Effect Sensing

The idea is grounded in electromagnetism - place an inductive element in the path of a changing magnetic field, and measure the induced voltage.

Open

Placement of magnetic sensor.

This makes the best placement of the IC on top of the trace delivering the current to be sensed. Ideally, the power trace is uniform in shape and the path of current is distributed evenly. This may be verified with PDN simulation and analysis.

IC Selection

https://www.digikey.ca/en/products/filter/linear-compass-ics/554?s=N4IgTCBcDaILYEMDmA7ApgFwJYGMAEAzmigQPYBOIAugL5A

Our sensing is one dimensional and we can save costs by picking a 1-dimensional (linear) magnetic sensor. Alternatively, we can pick more expensive ICs with a dedicated SMBus interface or additional sensing capabilities.

Useful Resources/Links

Buck Converters: Buck Converters

RPP: Reverse Polarity Protection Circuits

MOSFETS: https://uwarg-docs.atlassian.net/wiki/spaces/EL/pages/2318532681

CAN Circuit: https://uwarg-docs.atlassian.net/wiki/spaces/EL/pages/2524119043