# Jetson Nano Power Budget Analysis
## Self-Balancing Robot — 10W Envelope

Last updated: 2026-02-28
Target: Operate within 10W SoC power envelope (MAXN 10W mode)

---

## Power Modes

Jetson Nano supports two NVPModel power modes:

| Mode | GPU | CPU cores | CPU freq | Memory freq | TDP |
|------|-----|-----------|----------|-------------|-----|
| **MAXN (Mode 0)** | 128 core | 4 | 1.43GHz | 1600MHz | **10W** |
| 5W (Mode 1) | 128 core | 2 | 0.92GHz | 1600MHz | 5W |

For this robot, we target **MAXN 10W mode** with careful peripheral management.

```bash
# Check current mode
sudo nvpmodel -q

# Set 10W MAXN mode
sudo nvpmodel -m 0

# Set 5W mode (thermal/battery save)
sudo nvpmodel -m 1

# Monitor power in real time
sudo tegrastats
```

---

## Component Power Budget

### SoC (Jetson Nano Module)

| Component | Idle (W) | Load (W) | Peak (W) | Notes |
|-----------|----------|----------|----------|-------|
| CPU (4× Cortex-A57) | 1.0 | 3.5 | 4.0 | ROS2 + SLAM compute |
| GPU (128-core Maxwell) | 0.5 | 2.5 | 3.0 | Depth processing, ML inference |
| DDR4 RAM (4GB) | 0.3 | 0.6 | 0.8 | |
| eMMC / SD | 0.1 | 0.2 | 0.3 | |
| **SoC Subtotal** | **1.9** | **6.8** | **8.1** | |

### Peripherals (USB / GPIO)

| Peripheral | Idle (W) | Active (W) | Peak (W) | Interface | Notes |
|-----------|----------|------------|----------|-----------|-------|
| RealSense D435i | 0.3 | 1.5 | 3.5 | USB 3.1 | Peak during boot/init |
| RPLIDAR A1M8 | 0.4 | 2.6 | 3.0 | USB (UART adapter) | Motor spinning |
| STM32F722 bridge | 0.3 | 0.5 | 0.8 | USB CDC | Powered from Jetson USB |
| **Peripheral Subtotal** | **1.0** | **4.6** | **7.3** | | |

### Total System (from Jetson 5V barrel jack)

| Scenario | SoC (W) | Peripherals (W) | **Total (W)** | Margin |
|----------|---------|-----------------|---------------|--------|
| Idle | 1.9 | 1.0 | **2.9** | +7.1W |
| Nominal (SLAM running) | 6.8 | 4.6 | **11.4** | **-1.4W ⚠️** |
| Peak (all active, ML) | 8.1 | 7.3 | **15.4** | **-5.4W ❌** |

---

## Budget Compliance Strategy

The nominal load of **11.4W exceeds the 10W envelope** — mitigation required:

### Mitigation 1: RPLIDAR Power Gating
The RPLIDAR motor can be stopped when not scanning. The ROS2 driver handles this via DTR line.

| Mode | Savings |
|------|---------|
| RPLIDAR motor off | −2.2W |
| RPLIDAR idle | 0.4W vs 2.6W |

### Mitigation 2: RealSense Resolution Reduction
Lower RGB-D resolution reduces USB bandwidth and D435i processing:

| Profile | Power |
|---------|-------|
| 1280×720 @ 30fps | 1.5W |
| 640×480 @ 30fps | 1.1W ← **Recommended** |
| 424×240 @ 30fps | 0.8W |

### Mitigation 3: Jetson GPU Workload Scheduling
Avoid running depth inference and SLAM simultaneously at full throttle:

```bash
# Cap GPU frequency (reduce from max 921.6MHz)
sudo jetson_clocks --show
# Set conservative clocks
echo 614400000 | sudo tee /sys/devices/17000000.gp10b/devfreq/17000000.gp10b/min_freq
```

### Mitigation 4: STM32 Self-Powered
Power STM32 from robot's 5V bus (separate from Jetson USB rail):

| Option | Jetson USB load |
|--------|----------------|
| STM32 powered from Jetson USB | 0.5W |
| STM32 powered from robot 5V | **0W** (data only via USB) |

---

## Revised Budget with Mitigations

Applying: 640×480 D435i + RPLIDAR gating + STM32 self-powered:

| Component | Power (W) |
|-----------|-----------|
| CPU (SLAM, 4 cores) | 3.5 |
| GPU (depth processing) | 2.0 |
| RAM + misc SoC | 1.0 |
| RealSense D435i (640×480) | 1.1 |
| RPLIDAR A1M8 (active) | 2.6 |
| STM32 bridge (self-powered) | 0.0 |
| **Total** | **10.2W** |

**Near-compliant at 10.2W.** Further savings achievable by:
- Enabling RPLIDAR standby between scan cycles (−0.5W avg)
- Using 5W nvpmodel during motor-heavy phases

---

## Input Power Requirements

### Jetson Nano Power Input
| Spec | Value |
|------|-------|
| Input connector | 5.5mm / 2.1mm barrel jack |
| Input voltage | 5V DC |
| Recommended current | ≥4A (20W supply for headroom) |
| Absolute max | 5.25V |

> **Use a 5V 4A supply minimum.** A 2A supply will brownout under load.

### Robot Power Architecture (Recommended)

```
LiPo 3S (12.6V max)
       │
       ├─► DC-DC Buck → 5V 5A ──► Jetson Nano barrel jack
       │   (e.g., XL4016)
       │
       ├─► DC-DC Buck → 5V 3A ──► STM32 + logic 5V rail
       │
       └─► Hoverboard ESC ──► Hub motors (48V loop)
```

This isolates the Jetson 5V supply from motor switching noise.

---

## Real-Time Monitoring

```bash
# Live power telemetry
sudo tegrastats --interval 500

# Key fields:
# POM_5V_IN X/Y   — total input power (current W / average W)
# POM_5V_GPU X/Y  — GPU power
# POM_5V_CPU X/Y  — CPU power

# Log to file
sudo tegrastats --interval 1000 --logfile /tmp/power_log.txt &

# Parse log
grep "POM_5V_IN" /tmp/power_log.txt | \
  awk '{for(i=1;i<=NF;i++) if($i=="POM_5V_IN") print $(i+1)}' | \
  awk -F'/' '{sum+=$1; count++} END {print "Avg:", sum/count, "mW"}'
```

---

## Summary

| Metric | Value |
|--------|-------|
| Target envelope | 10W |
| Nominal (no mitigation) | 11.4W |
| Nominal (with mitigations) | ~10.2W |
| Compliant scenario | RPLIDAR standby + 640p D435i |
| Recommended PSU | 5V 4A (20W) |
| Power mode | nvpmodel MAXN (Mode 0) |