Peaks must be staggered/limited in firmware and by actual motors
A 5 A MINI blade fuse is retained. It is above the 4 A continuous design sum but still protects the PCB branch and harness. It does not make the TB6612 channels or 1.5 A motor jacks capable of 5 A each.
5 V Logic Input
The Pololu #5719 S9V11E2A is rated around 1.7 A continuous when input is close to output, after startup. At 5 V output and 85–95% efficiency, full-load input current is approximately:
Iin = 5 V × 1.7 A / (5 V × efficiency) = 1.79–2.00 A
Use a regulated 5 V source rated at least 2 A. The module limits startup current to roughly 700 mA until the output reaches regulation, so large external loads should remain disabled during startup.
5V0 Consumers
ESP32 DevKit Wi-Fi transient allowance: approximately 0.5 A peak.
Two TB6612 logic rails: small relative to motor current.
Remote breakout and user loads: remaining margin within the 1.7 A regulator limit.
C5 provides local energy storage for transient load steps but does not increase the regulator's continuous rating.
Protection Decisions
F1 retained
F1 is a through-hole PCB MINI blade fuse holder with ample holder current rating. A replaceable 5 A fuse is serviceable for a student robotics platform and matches the 4 A aggregate continuous motor design load.
Q1 retained
Q1 protects the complete motor branch from reversed 8 V input. The FQP47P06 is through-hole. At VGS near −8 V, the datasheet's typical curves imply roughly 0.1–0.2 V drop near 5 A; this is acceptable for an 8 V motor rail, though not a guaranteed worst-case value. Place it with copper area and airflow and do not obstruct its tab.
D4 retained
P4KE10A is a through-hole 400 W-class TVS with 8.55 V stand-off and 9.5–10.5 V breakdown range. It is placed after F1/Q1 so a sustained fault can open the fuse and so it clamps motor/harness transients locally.
Support-Passive Decisions
C1/C3, 330 µF 16 V radial: retained at each VMOT entry for local motor pulse current and cable/trace inductance. The socketed Pololu carriers contain their own supply capacitors, so no additional redundant 100 nF carrier parts are added.
C5, 470 µF 10 V radial: retained on 5V0 for ESP32 Wi-Fi and remote-load transients.
C7, 10 µF 10 V radial: retained on the 3.3 V breakout rail.
R1, 100 kΩ axial: retained as Q1 gate-to-source bias.
Grounding and Routing Decision
Both external supply negatives join one common GND. Motor return current should flow directly from U2/U3 and their local bulk capacitors toward J10, with the ESP32/breakout return connected to the same reference without forcing motor current through the logic region. A bottom GND fill is preferred, but motor-return traces/copper must still be sized for the aggregate current.
TB6612 Limitation
Each Pololu #713 TB6612FNG channel is approximately 1 A continuous. The 3 A figure is a short peak rating. This design must never be represented as supporting 2 A continuous per channel; 2 A continuous applies only to a special paralleled-channel use case, which this four-motor architecture does not use.