Comma.ai Panda Board
Thought for 5 sec
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.
Recommand NXP product
Thought for 14 sec
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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Design Notes and Power Budget
Status
Initial architecture and source-verification phase. Values below are conservative planning estimates and will be replaced or bounded by selected-part datasheet values before power-path sizing is finalized.
Preliminary 3.3 V Load Budget
Table
| Load | Typical estimate | Peak design allowance |
|---|---|---|
| STM32H725 at panda-class clock/peripherals | 180 mA | 300 mA |
| 3x CAN-FD transceiver logic/bus operation | 45 mA | 210 mA |
| LEDs and control pull networks | 10 mA | 30 mA |
| USB and protection leakage / sensing | 2 mA | 10 mA |
| Bring-up/debug margin | 15 mA | 50 mA |
| 3.3 V total | 252 mA | 600 mA |
Design target: 3.3 V rail rated at least 1 A continuous for thermal and transient margin. If the chosen CAN transceivers use a separate 5 V bus supply, their dominant bus-driver current moves to
5V_SYS and the 3.3 V load decreases.Preliminary Input Budget
At 3.3 V / 0.6 A peak, output power is 1.98 W. Allowing 85% worst-case conversion efficiency from a 6 V cranking minimum gives approximately 0.39 A input for the logic rail. Add CAN bus-driver, regulator quiescent, LED, and margin; size the protected input path for at least 1 A continuous and substantially higher surge immunity. Fuse/current-limit selection must be checked against hot-environment derating and final CAN transceiver supply architecture.
Source and Uncertainty Policy
- Official sources:
commaai/pandamaster branch board definitions and drivers;commaai/hardwareharness files; manufacturer datasheets. - Public repository confirms current panda firmware direction uses STM32H725 and contains
board/boards/red.h. - Connector mechanical identity and exact Red Panda USB-C relative geometry must not be claimed unless traceable to public CAD, drawing, or connector documentation.
- Automotive qualification statements are made only from the exact selected MPN datasheet.
Status
Preliminary 3.3 V Load Budget
Preliminary Input Budget
Source and Uncertainty Policy
