Comma.ai Panda Board

Thought for 5 sec

flux

Use TI TCAN3404-Q1 for each of the three CAN channels.

Why it fits:

CAN FD: supports data rates up to 8 Mbps
Automotive qualified: AEC-Q100
3.3 V MCU interface: compatible with the STM32H725
Wide bus fault protection: ±58 V
Low-power standby mode
Small VSON package: suitable for the 85 × 50 mm board

Recommended orderable part:

TCAN3404DRBRQ1
Package: 8-pin VSON/DRB, 3 × 3 mm
Quantity: 3

Use one TCAN3404-Q1 per channel, followed by the channel’s common-mode choke and PESD2CAN protection. Verify that the footprint includes the exposed thermal pad and connect it to ground with nearby vias.

hwarang2014

Recommand NXP product

Thought for 14 sec

flux

I recommend the NXP TJA1044GT/3 for each CAN channel.

Automotive AEC-Q100
CAN FD up to 5 Mbit/s
Designed for direct use with 3.3 V microcontrollers, including STM32H725
Standby and wake-up support
SO8 package, easier to assemble than VSON
Bus fault protection and excellent automotive EMC performance

Use three TJA1044GT/3 transceivers, one per CAN-FD channel. For improved signal integrity on long or highly branched automotive networks, consider the newer NXP TJA1443 CAN SIC transceiver, but it is larger and requires more support/configuration.

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Files

Schematic

Layout

3D View

Block Diagram

Architecture

Text
Vehicle Harness (12 V, GND, CAN1/2/3, optional verified aux)
  |
  +--> Automotive input protection
  |      fuse/current limit -> reverse polarity -> load-dump TVS -> EMI filter
  |               |
  |               +--> automotive buck --> 5V_SYS --> 3.3V regulator --> 3V3
  |
  +--> CAN protection/termination --> 3x automotive CAN-FD transceivers
  |                                      |
  |                                      +--> STM32H725 FDCAN1/2/3
  |
USB-C receptacle --> CC1/CC2 Rd, USB ESD, VBUS sense --> STM32H725 USB FS

STM32H725 core:
- all VDD/VDDA/VREF/VBAT/VCAP support and per-pin decoupling
- HSE/LSE only as required by verified panda firmware clock configuration
- BOOT0, NRST, SWD, UART/test access
- firmware-compatible status LEDs and CAN transceiver controls

Functional Groups and Sourcing Plan

Table

Block	Reference match	Decision
Automotive 12 V protection and regulation	None found in Flux reference organization	Datasheet-backed from scratch
STM32H725 core	None found	Datasheet-backed from scratch; pin assignment follows public panda `red.h` and STM32 alternate functions
Three CAN-FD channels	None found	Datasheet-backed from scratch using AEC-Q100 3.3 V CAN-FD transceivers
USB-C USB 2.0 device	None found	Datasheet-backed from scratch with 5.1 kΩ Rd per CC pin and low-capacitance ESD
Harness connector	Public-source verification in progress	Use closest verified family/part only; document mechanical uncertainty
Debug / indicators / bring-up	None found	From scratch, firmware definition + MCU datasheet

Inter-block Nets

Power: VBAT_RAW, VBAT_PROT, 5V_SYS, 3V3, 3V3_A, GND
CAN: FDCAN1_TX/RX, FDCAN2_TX/RX, FDCAN3_TX/RX, CAN1H/L, CAN2H/L, CAN3H/L
USB: USB_DP, USB_DM, USB_VBUS_RAW, USB_VBUS_SENSE, USB_CC1, USB_CC2
Control: transceiver standby/enable, selectable termination controls, LEDs, NRST, SWDIO, SWCLK, debug UART

Scope Boundary

Schematic phase only. PCB outline, exact connector-to-USB-C geometry, placement, routing, and proprietary mechanical details are explicitly deferred.

Architecture
Functional Groups and Sourcing Plan
Inter-block Nets
Scope Boundary