LV Architecture
The Low Voltage (LV) subsystem handles power conversion from 120V to 24V, along with the distribution of 24V to several systems on the car.
Relevant Regulations
TODO
Hardware Components
LV Carrier Board
Carries all the current from either the supplemental or main battery pack to the 24V input of the PDU
Houses all hats - Supplemental Monitoring, LV Mux, Vicor Carriers, PSOM
Contains MOSFETs, shunt resistors, and all external connectors
Provides power to LSOM using power mux → select between output of supp regulator and output of HV DC-DC (prefer DC-DC)
TODO: PSOM/LSOM connections → define type/# of each peripheral needed
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Maxi DC-DC Carrier Boards
Connects a Vicor Maxi DC-DC converter module to the LV Carrier
Supports both tin/lead (soldered) pins or InMate (socketed) pins
Contains all passives based on Vicor application notes
Connector: 2195620012 and 2195630012
Breaks out relevant sensing outputs to carrier board (PC, SC, Sense, etc.)
LV Mux Hat
Uses the LTC4421 IC to select between supplemental & main DC-DC outputs
Sets undervolt/overvolt/overcurrent thresholds
Only contains logic; no current flows through this board
Current sense Kelvin connections to carrier board
Provides GPIO outputs to PSOM for CH, DISABLE, FAULT, VALID for each source
SHDN driven by PSOM → NMOS to enable/disable LTC output
Supplemental Monitoring Hat
Monitor voltage before/after regulator
Current sense before/after - Kelvin connections to carrier board
Provides amplified analog outputs to PSOM (ADC) via carrier board
Overcurrent & reverse polarity protection
Power Distribution Unit (PDU)
Takes 24V output of LV Carrier and distributes to 12x LV outputs via export connector
Uses high-side switches with current monitoring + power protection
Interfaces with PSOM for software-defined current limiting and CAN status messages
Pump Control Board
Controls speed of liquid cooling pump and radiator fans for main battery
Collects data from temperature and flowrate sensors to tune control loop
Sends cooling data over CarCAN
Software Architecture
LV Carrier
PSOM reads supp voltage → drives LTC chip SHDN high (nominally pulled low to shutdown the car) → LV system ready