Power and Battery
The Neuro N6 power inputs, electrical limits, output rails and battery charging.
The Neuro N6 is powered from a 5 V supply on the USB-C port or the header USB pin, or from a single cell 3.7 V lithium ion or lithium polymer battery. An ideal diode OR-ing circuit selects between the 5 V supply and the battery, and regulators produce the board's 3.3 V and 1.8 V rails. When both a 5 V supply and a battery are connected, the on-board charger charges the battery.
Electrical characteristics
From the Neuro N6 datasheet.
| Parameter | Min | Typical | Max | Unit |
|---|---|---|---|---|
| Supply voltage, VBUS | 4.5 | 5 | 5.5 | V |
| Supply voltage, VBAT | 3.5 | 3.7 | 4.3 | V |
| Power consumption during inference, Neuro N6 with Neuro Vision OV5640 | 750 | mW | ||
| Output voltage, VDD_3V3 | 3.2 | 3.3 | 3.4 | V |
| Output voltage, VDD_1V8 | 1.75 | 1.8 | 1.85 | V |
| GPIO voltage range | -0.3 | 3.3 | 3.6 | V |
| GPIO current limit | 4 | mA |
The consumption figure was measured at 5 V and 150 mA from a bench supply on the USB pin. The GPIO current limit is the board's rating; the STM32N6 I/Os are specified by ST to sink or source up to 20 mA depending on the speed setting. The MCU itself operates from 1.71 to 3.6 V and at a junction temperature of -40 to 125 C, and derives its core voltage from an embedded switched-mode step-down regulator.
Power inputs
| Input | Range | Notes |
|---|---|---|
USB-C or USB header pin | 4.5 to 5.5 V | The same net, VBUS. Also powers the charger |
Battery connector or BAT header pin | 3.5 to 4.3 V | Single cell lithium ion or polymer only |
Only one 5 V supply is connected at a time. Connecting USB-C and a supply on the USB pin together causes contention that can damage the board or the supplies. The header follows the Adafruit Feather specification, so a Feather Wing that draws or supplies power on USB, BAT or 3.3V behaves as on other Feather boards. Non-rechargeable batteries and batteries of any other voltage are not connected.
Power circuit
From the Rev C schematic.
| Stage | Part | Notes |
|---|---|---|
| Selection | Two DZDH0401 ideal diode controllers driving PMPB15XP MOSFETs | Choose between VBUS and the battery. The output, VIN, feeds the regulators and the board-to-board connectors |
| Charger | TP4054 | Linear, 500 mA, powered from VBUS only |
| 3.3 V rail | AP3441 buck converter | Logic, radios, sensors, header 3.3V |
| 1.8 V rail | AP3441 buck converter | Memories and the core supply input |
| Analogue and always-on 1.8 V, 3.3 V | ETA5055 LDOs | ADC reference (AREF), PLLs, CSI and USB analogue supplies |
| USB protection | USBLC6-2P6 | ESD protection on the USB data lines |
Output rails
| Rail | Available for external devices | Notes |
|---|---|---|
| VDD_3V3 | 1000 mA | Limited by trace thermal performance; final figure pending |
| VDD_1V8 | 1000 mA | Same |
| VIN, on the board-to-board connectors | 1000 mA | Same |
| VDDA_1V8 (VREF) | 100 mA | Analogue reference, low power |
The total demand on each rail is kept within its capability, and the selected supply must cover the whole system. Insufficient supply causes voltage drop or brownout that can damage devices on the affected rail.
Battery
A single cell lithium ion or lithium polymer battery on a JST-PH two-pin connector (S2B-PH-SM4-TB, mating PHR-2). The linear charger charges at 500 mA from USB whenever USB is connected. The BAT header pin is in parallel with the connector.
The charging status LED shows the charger state: red while charging, flashing at 20 Hz when USB is connected with no battery, and off when charging is complete or USB is absent. The charger may become hot to the touch during charging.
Battery voltage sense
The battery voltage is divided by 100k over 56k and presented to the ADC on PF6, so a 4.2 V cell reads about 1.51 V. The pin is not exposed as a battery reading in the Arduino core.
External supplies
Modules requiring more than the rails supply, such as the A7683E LTE modem with 2 A peaks, are powered from their own 5 V supply with a common ground to the board. See LTE Modem.
Thermal
The board may become warm during heavy operation. Initial testing with the Neuro Vision module found no temperatures that would cause burns under normal contact. Safe operation is validated before deployment.