docs/references/THERMAL.md
T4000 thermal — facts from TDG-12271-001 v1.3
Source: jetson_thor_thermal_dg_tdg-12271-001v1.3.pdf NVIDIA Developer download, 24 pp, May 18 2026. pdftotext 2026-09-02.
This is the SOM thermal / mechanical interface, not a product cooler. Customer designs the cooler that sits on the TTP. NVIDIA sells neither a cine body nor a fanless 70 W promise.
Limits (Table 2-1)
| T4000 | T5000 | |
|---|---|---|
| TTP max (must not exceed) | 75 °C | 80 °C |
| Recommended SoC (Tj) | 90 °C | 90 °C |
| SoC max / specified clocks | 115 °C | 115 °C |
| Hardware reset (thermal trip) | 118 °C | 118 °C |
| TMP default / throttle | 70 W / 90 W | 120 W / 130 W |
Reliability (note 3): 95 % of 5-year life at 90 °C Tj, 5 % at 118 °C. Running hot shortens the module. Software throttle at 90 °C; hardware throttle then reset at 118 °C. Trip settings cannot be changed. Sensor uncertainty ±3 °C — design headroom under 90 °C, not onto it.
Datasheet companion (DS-11945): T4000 air-cooled not guaranteed above 45 °C ambient. T5000: not guaranteed above 25 °C ambient. Sun-load on a black cine body is the 45 °C problem, not the lab.
What the TTP is
The module ships with a Thermal Transfer Plate covering the whole PCB, internal heat spreader + heatpipe onto the SoC. Contact patch 62.5 × 81.4 mm. Full-face contact.
- Cooler (passive or active — NVIDIA’s words) bonds to the top of the TTP with customer TIM.
- Mount: M3 screws through cooler + TTP + backside stiffener into standoffs. Connector cannot carry the module.
- Do not open the TTP. Warranty void (Fig. 1-3 note).
TMP = steady-state average board watts (size the cooler). EDP = power-supply transients (size the PSU). Do not confuse them.
The number that matters: θpa
θjp (SoC → TTP), Table 3-1, T4000:
| Workload | θjp |
|---|---|
| Balanced (CPU+GPU+DRAM — our AI+encode case) | 0.24 °C/W |
| Unbalanced (CPU-only hotspot) | 0.30 °C/W |
At 70 W balanced: SoC is 16.8 °C above TTP. Hold SoC at 90 °C → TTP 73.2 °C (2 °C under the 75 °C cap). TTP and SoC limits are almost the same on T4000; T5000 is looser (80 °C TTP, θjp 0.18).
Required cooler, TTP → ambient:
θpa ≤ (73.2 − Tamb) / 70 °C/W| Tamb | θpa max at 70 W | θpa max at 40 W |
|---|---|---|
| 25 °C | 0.69 | 1.21 |
| 35 °C | 0.55 | 0.96 |
| 45 °C (NVIDIA air-cooled ceiling) | 0.40 | 0.71 |
NVIDIA’s own example (T5000, 60 W, 50 °C amb) needed 0.49 °C/W. That is a serious cooler.
Catalog coolers vs those numbers
ATS Thor (fits TTP, Digi-Key):
| PN | Kind | Envelope | Mass | Claim |
|---|---|---|---|---|
ATS-NVP-3739 | “Passive” extrusion | 87 × 101 × 20 mm | 168 g | 100 W @ 50 °C with 500 LFM |
ATS-NVA-3740 | Fan in the fins | same | 104 g | 95 W @ 50 °C |
ATS-NVA-3752 | Blower | 92 × 101 × 29 mm | 174 g | 175 W — T5000, skip |
500 LFM ≈ 2.5 m/s. That is chassis airflow, not still air. ATS passive at 200 LFM is ~0.45 °C/W — works at 25–35 °C with a fan somewhere in the box. Natural convection on an 87 × 101 × 20 mm fin stack is ~1.5–2.5 °C/W. At 2 °C/W × 70 W = 140 °C rise. TTP would be ~165 °C. A small “passive” brick does not cool 70 W in still air. The word passive in the ATS catalog means “we didn’t put a fan on this extrusion; your system air does.”
CTI Rogue-T5 SKU AGX302-02Y is “Thor Passive Cooling” on a T5000 assembly (~$8.4k). Same story: a chunk of aluminum, not a silent handheld.
Radiators, not a flock of fans
Duke preference: better heatsinks/radiators, not lots of fans. TDG allows either. Physics of 70 W:
A cine-sized metal shell (≈0.12 m², six sides of ~150 × 120 × 80 mm) at 8 W/m²K natural convection and 40 K rise dumps ~38 W. Fins might get 50 W. 70 W fanless in a PYXIS-class envelope is not honest. Record-only (NVENC + CSI, AI dropped) is more like 15–30 W — that is fanless-capable.
Ranked thermal architectures (best first for this product):
- Body is the radiator. TTP → TIM → vapor chamber / heatpipes → magnesium or aluminum cine shell, black anodized, finned back. Honest ~40 W still air. Matches “drop AI, never record.”
- Heatpipes to a V-mount / rear radiator + one large slow fan. One 80–92 mm on a fin stack, PWM from Thor (TDG ch. 4.2, default table 750–2900 RPM). 70 W AI. Cine already sounds like this (RED). Prefer this over three tiny blowers.
- Remote radiator. Heatpipes or a liquid loop to a battery-plate or pack. Optical body stays cool and silent. More plumbing.
- Catalog ATS/CTI HS on the lab bench. Measure TTP with a thermocouple at Fig. 3-2 before any custom body CAD.
Do not: resin as a heat path; sealed plastic; many small fans; opening the TTP; promising sun-load before a metal prototype.
Thor PWM + tach exist if we use one fan. Default fan table is an example; we must qualify our own cooler in software (ch. 4.2 note 1).
Body-integration hold
Thor-in-body is still the product shape. It is not a solid plan until we pick 1 vs 2 vs 3 above and measure a T4000 + Rogue-T5 + ATS stack. Lab remains the AGX kit in resin (kit has its own fan; leave it). Production body is metal. See POWER.md, ENCLOSURE.md.
Don’t
- Treat ATS “100 W passive” as still-air 100 W
- Design a sealed magnesium brick at 70 W without a radiator path
- Run at 90 °C Tj as a lifestyle — that’s the reliability knee
- Skip TIM or mount on the B2B connector alone