jetson-agx-thor-baseboard Design Analysis

AI-Assisted — This is a 15-sheet hierarchical carrier board for an NVIDIA Jetson AGX Thor compute module. The module mates through J1, a Molex 203456-0003 Mirror Mezz hermaphroditic connector. J1 carries the module's input supplies (SYS_VIN_HV, SYS_VIN_MV and SYS_VIN_SV), the power-sequencing and reset handshakes, the UPHY SerDes lanes and reference clocks, four USB 2.0 ports, eight two-lane CSI camera ports, four DisplayPort/HDMI outputs, and the I2C, SPI, UART, I2S, CAN and GPIO banks. The carrier fans these out to USB Type-C, PCIe M.2, SFP28, camera FFC and FMC expansion interfaces. It adds a TPM, configuration EEPROMs, current monitoring, a coin-cell backup and always-on power control.

USB and Type-C Subsystem

The USB Hub sheet is built around U21, a Microchip USB7252C 4-port USB 3.2 Gen 2 hub with native Type-C support. The board's configuration straps disable downstream ports 3 and 4 (both D+ and D- strapped to +3V3), so the hub serves its two Type-C downstream ports. Per the Microchip datasheet (Datasheet) the hub is rated for -40 °C to +85 °C. Its 25 MHz reference comes from the ECS-2016MV oscillator Y2.

U30 is a TI TPS65988 dual-port USB Power Delivery controller. It runs firmware from the 8 Mbit SPI NOR flash U29, which can be programmed in-circuit through Tag-Connect J4. Per the TI datasheet (Datasheet), its integrated power paths carry up to 5 A each and its VBUS pins tolerate up to 22 V in operation.

The recovery USB port uses U56, a TI HD3SS3220 Type-C DRP controller with an integrated 10 Gbps 2:1 SuperSpeed mux. The fitted HD3SS3220I grade is rated -40 °C to +85 °C per the TI datasheet (Datasheet).

DisplayPort Alternate Mode is provided by U33, a TI TUSB1046-DCI USB-C/DP crosspoint redriver. It supports 10 Gbps USB and 8.1 Gbps HBR3 per the TI datasheet (Datasheet).

A dedicated debug Type-C port uses U34, an FTDI FT230X USB 2.0 Full Speed to UART bridge rated to 3 Mbaud. It has its own NCP718 3.3 V LDO U32 (FTDI_3V3) and is rated -40 °C to +85 °C per the FTDI datasheet (Datasheet).

Every Type-C VBUS output is switched and current-limited by an AP22615 load switch. The board has five USB Type-C receptacles (J3, J5, J6, J7, J9), and the Type-C and SuperSpeed lines are protected by TPD4E05U06 and TPD1E0B04 ESD arrays.

PCIe, Networking and Expansion

J13 is an M.2 Key M socket carrying a four-lane PCIe link with SMBus and sideband signals. J14 is an M.2 Key E socket carrying two PCIe lanes plus USB, SDIO, UART and PCM for wireless modules. Both are powered from the 3V3_M2 rail.

The 100 MHz HCSL oscillator Y1 supplies a PCIe reference clock. J12 is an Amphenol SFP28 receptacle in cage J19, clocked by the 156.25 MHz HCSL oscillator Y5. Its management I2C runs on the module's I2C3 bus through ESD array U73.

J18 is a Samtec ASP-208571-01 FMC connector. It exposes a large block of module signals, the I2C0 bus with configuration EEPROM U2, and the I2C2 management bus. It is supplied from the +3V3_FMC and +3V3_AUX rails.

Camera Interface

Two 50-position Würth FFC connectors, J10 and J11, carry the CSI camera lanes. Their control buses come from U43, a PI4MSD5V9548A 8-channel I2C multiplexer at address 0x70 on the module's I2C4 bus. Two mux channels are routed to each FFC, and the camera I2C supplies are the CSIA_I2C_VCC and CSIB_I2C_VCC rails. NTS0102 and NTS0104 translators and SN74AXC8T245 dual-supply transceivers adapt module I/O levels to the peripherals.

Security, Management and Monitoring

The module's I2C2 bus is the board management bus. It hosts:
- U14, an Infineon SLB9673 TPM 2.0 at 0x2E, rated -40 °C to +105 °C per the Infineon datasheet (Datasheet);
- the TPS65988 PD controller;
- EEPROM U54;
- five INA219 bidirectional current/power monitors (U22, U50, U60, U66, U76);
- U71, a PCAL6408A 8-bit I/O expander strapped to 0x20.

The module's I2C5 bus is brought out to two JST SH 4-pin headers, J16 and J17. A PicoBlade header J15 provides the fan connection from FAN_VDD.

Power Control and Always-On Domain

Board power-on is handled by U70, a MAX16150 latching pushbutton controller, with U72, a TPS3840 3.0 V voltage supervisor, and U3, an LTC6994 programmable delay that shapes the power-up timing. The always-on domain runs from +5V_AON and +3V3_AON. BT1, an MS621FE rechargeable lithium coin cell, backs up the module's PMIC_BBATT input, and the 32.768 kHz oscillator Y3 provides a low-frequency clock. User controls are five tactile switches and a slide switch, with green and yellow status LEDs throughout.

Power Tree

Main input enters on J2, a Molex Mini-Fit 2x3 connector. U9, a MAX16013 controller, provides overvoltage and reverse-voltage protection with SiSS05DN P-channel power MOSFETs, separating VCC_NO_OVP from the protected VCC/VCC_IN rails. U63 and U64 are LTC4412 ideal-diode controllers that implement power-path OR-ing.

Six Vishay SiC437A synchronous buck regulators produce the primary rails: U8 on 12V_OUT, U11 on 16V_OUT, U12 on 5V_OUT, U13 on 3V3_OUT, U65 on 20V_OUT and U75 on 5V_AON_OUT. Per the Vishay datasheet (Datasheet), the SiC437A accepts 4.5 V to 28 V input and delivers 12 A continuous. It regulates against a 0.6 V reference with switching frequency selectable from 300 kHz to 1 MHz, and is rated for -40 °C to +105 °C ambient.

Two TPS564247 bucks generate the low-voltage rails: U7 produces 1V8_OUT through L7, and U69 produces 1V15_OUT through L5. U79, an LD39100 1 A LDO, produces 3V3_LDO and, through R63, the +3V3_AON rail.

The distributed rails are +20V, +12V, +5V, +5V_SOM, +5V_AON, +3V3, +3V3_AON, +1V8 and +1V15. Two USB PD high-voltage rails, USBPD1_HV and USBPD2_HV, are also distributed. The USB VBUS rails (USBC0_VBUS, USBC1_VBUS, USBC2_VBUS, USBC3_VBUS and USBC4_VBUS) are sourced by AP22615 switches U40, U35, U23, U18 and U20 respectively.

Temperature Rating

The board's ambient operating range is set by its narrowest-rated parts. U33 (TUSB1046-DCI) is rated 0 °C to 70 °C, and U30 (TPS65988) is rated -10 °C to +75 °C ambient. This places the assembled board in the 0 °C to 70 °C commercial class. The hub, PD mux, UART bridge, TPM and buck regulators are all rated to at least -40 °C to +85 °C.