Jetson Orin baseboard: how much voltage reaches the module

The question

NVIDIA sets a minimum voltage at the module's VDD_IN pins. Between the board's input and those pins, some voltage is lost: in the copper, and in the parts the current flows through. How much is left at the pins? How close is that to NVIDIA's minimum?

The board feeds the module in one of two ways. An Orin NX leaves its MODULE_ID pin floating. That turns on the eFuse U48, which feeds VDD_IN from the board's 9 to 20 V input through two P-FETs, Q15 and Q18. A 5 V-only module ties MODULE_ID to GND. It is fed from the carrier's 5 V buck through the eFuse U29. An NVIDIA forum moderator names the Orin Nano as a 5 V-only module; that is a forum post, not a data sheet.

Terms such as eFuse, P-FET and buck are explained at the end, under Words used on this page.

In short

How to read the 3D view

• You see the board's eight copper layers, stacked. F.Cu, the top layer, is at the top. B.Cu, the bottom layer, is at the bottom. In1.Cu to In6.Cu are inside. The gaps between the layers are drawn 10 times thicker than they are; the Layer spacing slider changes this.
• Colour shows one of two things, chosen under View. Current density: how crowded the current is in the copper, in amps per square millimetre (A/mm²). Darker means less, lighter means more. The top band is open: 300 A/mm² and above. Voltage: how many mV the copper sits below its supply, or above 0 V on GND. Each rail has its own scale in the legend. Thin lines mark equal steps, and pins mark the worst point of each.
• In the legend, checked max is the highest current density averaged over 0.1 mm: the value pdnsim compares with its rule of thumb. raw max is the highest value in a single mesh element, with its place.
• Grey with hatching: pads and via lands. pdnsim treats each as one voltage, so no density is drawn there.
• Dark copper: another rail of the same scenario; choose it under Rail. Grey outlines: copper with no computed current in this scenario.
• Cylinders between the layers: vias. Lighter and wider means more current, from 0 to 2 A.
• Labels name the parts. J12 is the board's power input and J15 the module's socket. Light labels mark the parts on the chosen rail's path.
• Tick flow to see which way the current goes. Streaks move along the copper and dots move through the vias: ivory on the supply, mint on GND. Their speed and number are not to scale.
• Drag to turn the board, and scroll or pinch to zoom. Point at the copper, or tap it, to read its values in the line under the view. On a phone, a drag on the board turns it; to scroll the page, drag on the text.
• New here? Start with Follow the current: it moves the view along the module's path, one step at a time.

Follow the current

The margin at the module's pins

Why there is no verdict

Where the voltage goes

Loads on this rail

What pdnsim flags on this rail

Notes on the text

What was and was not modelled

How the view is drawn

Numerical convergence, not accuracy

Words used on this page

IR drop (voltage drop)

The voltage lost when a current (I) flows through a resistance (R). pdnsim computes it in the board's copper, and adds the drop across each part in the path at the part's stated resistance.

pdnsim

Simulibrium's DC voltage-drop tool. It reads a KiCad board file and computes the voltage and the current in its copper.

DC

A steady current that does not change over time. pdnsim computes no transients and no switching.

Carrier board (baseboard)

The board the module plugs into. It brings power and connectors to the module.

Module (SoM)

The NVIDIA Jetson Orin NX or Orin Nano computer that plugs into the carrier's SO-DIMM socket, J15. SoM means system on module; this page uses both words.

SO-DIMM socket

The edge-connector socket (J15) that holds the module.

VDD_IN

The module's main power input, on J15's pins 251 to 260. NVIDIA's limits apply to the voltage between these pins and the module's GND pins.

GND (ground)

The return path to the supply, taken as 0 V. The current comes back through the GND copper, and that copper loses a little voltage too.

Supply drop and ground rise

The voltage lost on the way out, in the supply's copper and parts, and on the way back, in the GND copper. Their sum is the total drop.

Rail

One supply path from a source to its loads. Each scenario here has three rails, listed under Rail. Each is shown together with GND.

Scenario

One operating case we chose (module, power mode, input voltage), solved as one DC solution at a constant module current. The runs are lettered A to G; four of them have a 3D view.

Margin

How far the computed voltage at the module is above, or below, NVIDIA's minimum.

Bound, bound case

A bound case takes the inputs we name at their worst. A margin is a bound only if every input is at its worst, the ones not modelled included, so neither E's nor G's margin is one. D's current is NVIDIA's bound on the module's current.

Current density (|J|, A/mm²)

The current per square millimetre of copper cross-section: how crowded the current is. High values heat the copper.

Checked max and raw max

Checked max is the highest current density averaged over 0.1 mm, the value pdnsim compares with its rule of thumb. Raw max is the highest value in a single mesh element, with its place.

Heuristic

A rule of thumb, such as the 35 A/mm² or the 1 A per via that pdnsim's findings name. pdnsim uses it to point at places to look at, never as a pass or fail.

Layer

One of the board's copper sheets. In KiCad's names, F.Cu is the top (front), B.Cu the bottom (back), and In1.Cu to In6.Cu are inside.

Via, barrel, via land, plated hole

A via is a small plated hole that joins copper on different layers. Its wall is the barrel, and its copper ring on a layer is the via land. A part's pin in a plated hole joins layers the same way.

Pad and pin

A part's pin is soldered to a pad, so "J12 pin 1" and "J12 pad 1" are the same point. pdnsim treats each pad and via land as one voltage ("one potential").

Net

KiCad's name for one set of connected copper, such as VCC_IN, VDD_SoM or SoM_VIN.

eFuse

An electronic fuse: a chip that switches the power on and limits the current. U48 feeds an Orin NX; U29 feeds a 5 V-only module.

P-FET

A transistor used as a switch. Q18 switches the input. Q15 works as an ideal diode: it blocks reverse current with little loss.

|VGS|

The gate voltage that turns a FET on. The lower it is, the higher the FET's resistance.

Pulse test

A data-sheet value measured in short pulses, so the part does not heat during the test.

I²R

The power turned into heat in a resistance: the current squared times the resistance.

Buck, setpoint, LDO

A buck is a regulator that steps a voltage down: U1 makes the carrier's 5 V and U40 its 3.3 V. Its setpoint is the output voltage it aims for. An LDO is a simpler linear regulator.

Jumper (0 Ω)

A resistor of nearly zero resistance used as a link, such as R287 and R172.

MODULE_ID

A module pin that tells the carrier which kind of module is fitted. On this board it selects the power path.

MAXN_SUPER, 25 W*, TDP

MAXN_SUPER and 25 W* are NVIDIA's names for power modes. The number in a mode's name is its power budget, not a measured draw. TDP is that budget: NVIDIA's module slows down when its power goes beyond it.

Throttling, OC1 and OC2

Throttling: the module slows its CPU and GPU. In NVIDIA's table, OC1 is the under-voltage event and OC2 the average-power limit.

Absolute maximum (IDDMAX)

A value NVIDIA says must never be exceeded. IDDMAX is the Orin NX data sheet's absolute maximum for the VDD_IN current.

Constant current, constant power

A load that draws a fixed current, or a fixed power. At a constant power, the current rises as the voltage sags.

Stated resistance

A part's resistance taken from its data sheet, not computed by pdnsim.

Verdict, judge: false

A verdict is pdnsim's pass or fail. There is none here: the copper thickness is not confirmed, and we set judge: false, a line in pdnsim's configuration that tells it not to judge a rail.

Current basis

What kind of current a number is, such as an average or a peak. In the scenarios with a 3D view the module's current is an average, so pdnsim labels its numbers "at average current, not a verdict".

results.json

The file of results pdnsim writes for each run. The findings on this page are quoted from it.

Mesh, nodes, convergence

pdnsim splits the copper into many small pieces (a mesh; nodes are its points) and refines it until the answer stops changing. That checks the arithmetic, not the accuracy.

Our arithmetic, not run

A number we worked out by hand from pdnsim's results, not from a pdnsim run.

Sources and credits

A plain-text summary of this page's numbers, for reading without JavaScript or by an AI assistant: report.txt. It is generated from the same data files.

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