Due Dates:

• Requirements/Considerations -

• Component Selection -

• Initial Schematic -

• Initial Layout -

• Rev. A Ordered -

• Firmware/Testing -

Description/Purpose

• The LV Mux board automatically manages low-voltage power source selection in the solar vehicle. It switches between the main 24V supply from the DCDC converter and a supplemental 24V battery, ensuring compliant power delivery during ignition, normal, and fault conditions.

Requirements

• Within-system & inter-system requirements

Source Selection & Control

• The LV Mux selects between DCDC power and the supplemental battery using the LTC4421 IC. Selection relies on user-configurable voltage thresholds set by external resistive dividers defining undervoltage falling (UVF), undervoltage rising (UVR), and overvoltage (OV) points. These thresholds ensure the DCDC source is preferred and selected when its voltage is within a valid window, with automatic fallback to supplemental battery during ignition or fault conditions when DCDC voltage is below the UVF level—preventing power interruption and protecting batteries.

PSOM connections

• The PSOM connections interface the board with external monitoring and control peripherals, enabling communication using SPI and I2C protocols along with CAN bus lines. These connections facilitate debugging and testing. Pull-up resistors (100kΩ) on many signal lines ensure signal integrity when interfacing with high-impedance devices or open-drain outputs on the board

Charge pump

• The board uses LTC4421’s internal charge pump to drive the gates of external N-channel MOSFETs above the source voltage, which ensures these MOSFETs are fully enhanced (turned on). Improving efficiency Charge pump output (CPO) is stabilized by an external capacitor between CPO and CPOREF pins, ensuring smooth and reliable gate driving during source switching events

LEDs

• Status LEDs are connected to the LTC4421’s internal regulated low-voltage supply rail (INTVCC) through buffers (74LVC2G07 or equivalent) to provide clear indication of power states and faults.

Shutdown logic

• Shutdown and protection logic on the LV Mux leverages the LTC4421’s DISABLE and SHDN pins to actively disconnect input power channels during fault conditions, undervoltage, or manual shutdown requests.

External Power cascading?

Application Note

Context

Location of the board:

Connection List

Main

Schematics

Circuit Components

Layout

Github link: PS-LVCarrierPCB/Hardware/PowerMuxPCB at main · lhr-solar/PS-LVCarrierPCB

PCB:

3D Model

Firmware

Drivers

High-Level (Block Diagram)