Jetson/Jetson TK1 Power

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Revision as of 21:17, 6 June 2014 by Shervin.emami (talk | contribs) (Added some info about replacing the fan with a heatsink)
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Jetson TK1 power draw

The Tegra K1 SOC is aimed at tablets and thus uses between 2W to 5W of power during typical use, but this varies greatly depending on how much you manage to push the 4 CPU cores, 192 GPU cores, DRAM, camera ISP and codec hardware to their limits. That is just for the SOC, so clearly the Jetson TK1 board requires a lot more power than this if you will also use various expansion ports & accessories.

The Jetson TK1 board is rated for 12VDC input, and has been tested with voltages between 10.8V to 13.2V. Note that SATA disks require a fairly precise 12V, so you shouldn't be using voltages at those ranges if you will use SATA hard drives. It is known that the Jetson TK1 board won't turn on at less than 9.5V and it will likely be damaged at 16V or above. It may be possible to power the Jetson TK1 board somewhere in the 9.5V to 10.8V range or the 13.2V to 16V range but NVIDIA has not tested this.

The absolute max power draw of Jetson TK1 if you push everything to the limit and use every port including SATA and PCIe is 4.8A @ 12V (60W). So you can probably get by with smaller 20W or 40W power supplies if you don't use too many accessories, but a 60W power supply will ensure you never have any lack of power onboard.

Replacing the fan with a heatsink

The Jetson TK1 board comes with a 12V 1.1A (13.2W) fan+heatsink combo on the SOC, to ensure the board is always safe to touch by humans even when running the CPU & GPU at max performance for long durations. But some users many way to remove the fan and replace it will a passive heatsink, to reduce power or to get rid of the fan noise.

The Tegra K1 SOC is designed for tablets that use a small heatsink or heatspreader plate, thus clearly it doesn't require a powerful fan. But tablets aren't expected to run at full performance for long periods, and you also can't touch the SOC of a tablet with your bare fingers, so NVIDIA decided to use a fan for Jetson TK1. If you wish to replace the fan with a heatsink, take into account that if you will be pushing the SOC to its limits for long durations, the SOC might be using 10W or more of power that you must dissipate with a large heatsink and/or external fan and/or attaching a heatspreader to the metal case of your overall device, otherwise the Tegra thermal management may reduce the available speed to ensure it wont overheat.

It hasn't been tested by NVIDIA, but rough estimatations suggest that a 1.5" x 1.5" x 0.8" Aluminium heatsink (such as an Aluminium Malico MBH33002 or Copper Malico CMBA054949 north-bridge heatsink) would allow running intense code continuously while not getting hot enough for the SOC to limit its performance or burn human skin.

Limiting power use

Note: Debugfs and non-upstream sysfs nodes aren't guaranteed to remain unchanged in future releases.

Reducing power if display isn't required

As root:

echo -1 > /sys/kernel/debug/tegra_hdmi/hotplug
echo 4 > /sys/class/graphics/fb0/blank

Restricting to low-power core only

Restricting the CPU to the low power companion core can significantly reduce peak power (if running on a power-limited battery pack, for example). It is still a Cortex-A15 core with NEON and 32KB L1 cache and 512KB L2 private cache, but obviously at lower performance than the 4 main cores. As root:

echo 0 > /sys/devices/system/cpu/cpuquiet/tegra_cpuquiet/enable
echo LP > /sys/kernel/cluster/active

Powering with a battery

Compatible plug

Slightly under-powered step-up converter

More powerful step-up converter

Both of these step-up converters will work either from a USB battery or directly off a LiPo battery. Note that most USB batteries can only produce 5V@2.1A ~= 10W at best, which is less than the TK1 draws at max power consumption.