A microcontroller (MCU) pin can’t directly output “maximum current + high voltage.” In theory, an MCU GPIO is a logic-level signal source (3.3 V / 5 V, limited current), and any “high voltage / high current output” is created by an external power stage that the GPIO controls.
What you’re really doing is simulating a “power output” that is commanded by a microcontroller:
MCU GPIO (logic) → level shift / gate drive → power switch (MOSFET/IGBT/high-side switch) → external HV supply → load
Below: theory first, then real, concrete part-number examples (no vendor names needed in your final article if you prefer, but I’m using well-known model numbers here so it’s actionable).
1) Theory: model the MCU output correctly
1.1 GPIO is not a power source
A GPIO pin behaves roughly like:
- A voltage source (VDD, e.g., 3.3 V)
- With finite output resistance (so voltage droops as current increases)
- With strict absolute max limits (overcurrent can cause latch-up, permanent damage)
So you should never “maximize” current from the pin. Instead you use it as a control signal.
1.2 High voltage and high current come from the external supply
To simulate an MCU “power output,” you provide:
- HV supply (12 V / 24 V / 48 V / 60–400 V, depending on your target)
- Current capability (amps to tens of amps)
- A switch (MOSFET/IGBT) that connects/disconnects the load
- Protection (flyback diode, TVS, current limiting, fusing)
1.3 Two switching topologies
Low-side switching (most common, simplest)
High-side switching (when load must stay at ground)
- Switch connects +HV to load
- Best for: automotive-style wiring, grounded loads, “sourcing” outputs
1.4 “Maximum current” is a power-stage problem
If you want “max current simulation,” you control it by:
- A bench supply current limit (simple)
- A sense resistor + current limiter (accurate)
- A high-side/low-side current monitor and firmware control
- An electronic fuse / hot-swap controller for safety
1.5 If you need analog high-voltage outputs
- For 0–10 V: PWM/DAC → op-amp (powered from higher rail) → 0–10 V
- For 4–20 mA: PWM/DAC → current-loop driver → loop supply (often 24 V)
2) Practical simulation recipes (what engineers actually do)
Recipe A — High-voltage ON/OFF (DC loads): MOSFET low-side
Goal: MCU pin “simulates” switching a 24 V load at several amps.
Blocks
- MCU GPIO → gate resistor + pulldown
- Logic-level N-MOSFET (or gate driver + MOSFET for bigger loads)
- Flyback diode if inductive
- TVS on supply for transient suppression
Why it works: MCU only charges/discharges a gate (microamps average); the MOSFET and supply deliver amps.
Recipe B — High-side “sourcing” output (automotive/industrial)
Goal: Simulate a PLC/ECU output that sources 24 V to a load.
Use either:
- A high-side switch IC (easiest + protections)
- Or P-MOSFET + driver (good for moderate voltage/current)
Recipe C — High voltage (tens to hundreds of volts): isolated gate drive + MOSFET/IGBT
Goal: Simulate an MCU controlling a 100–400 V power stage (e.g., DC bus).
You typically need:
- Isolation (digital isolator or optocoupler)
- Gate driver (often isolated)
- MOSFET/IGBT with correct voltage/current ratings
- Snubbers/TVS, creepage/clearance rules, and safe probing
3) Real-world example builds (with actual model numbers)
Example 1: “STM32 outputs 24 V / 5 A ON/OFF” (industrial load)
MCU (logic source): STM32F103C8T6 (3.3 V GPIO)
Power stage (low-side):
- MOSFET: IRLZ44N (easy-to-find logic-level MOSFET; fine for learning/low-frequency switching)
- Gate resistor: 33 Ω
- Gate pulldown: 100 kΩ
- Flyback diode (inductive loads): SS54 or 1N5822 (Schottky, choose current/voltage margin)
- Supply protection: SMBJ33A TVS (for 24 V-ish rails; pick TVS rating based on your system)
- Add a fuse on the 24 V input
How to “simulate maximum current” safely:
- Use a bench supply at 24 V
- Set current limit to 0.5 A first, verify switching
- Increase limit gradually to your target (e.g., 5 A)
- Start with a dummy load: a power resistor (e.g., 4.7 Ω / 50 W) or an electronic load
Notes:
- IRLZ44N is not a “modern best-in-class” MOSFET, but it’s a classic demonstration part.
- For faster PWM, higher efficiency, or tight thermal limits, you’d select a newer MOSFET with lower RDS(on) at VGS=2.5–4.5 V.
Example 2: “Arduino-like GPIO simulates a 12 V relay driver”
*MCU: *ATmega328P (5 V GPIO)
Driver stage (because relay coils are inductive):
- Transistor: 2N2222 (or similar BJT) or a small logic MOSFET like AO3400A
- Flyback diode: 1N4148 (small relay) or 1N4007 (general) / SS14 (fast Schottky)
- Base/gate resistor: BJT base ~1 kΩ; MOSFET gate ~33 Ω
- Pull-down: 100 kΩ (MOSFET)
Why this is a good “simulation”:
It mimics what a real MCU-controlled output stage does: logic controls a switch, and the external supply drives the coil.
Example 3: “3.3 V MCU simulates a 24 V high-side output with protections”
MCU: STM32G0 series (3.3 V GPIO)
High-side switch IC: BTS500xx / VNQxxx-style high-side switch families (automotive protected high-side switches)
These parts typically include:
- current limit
- thermal shutdown
- short-circuit protection
- diagnostic output (optional)
How to test:
- GPIO drives the enable/input
- Put load between output and ground
- Use supply current limit + fuse for safety
- Scope the output during switching; watch inrush
(Exact suffix depends on your current rating/channel count; choose according to your “max current” target.)
Example 4: “MCU simulates high voltage (e.g., 200–400 V) switching”
MCU: STM32F4 series (timers for PWM)
Isolation + driver:
- Digital isolator: ADuM1100 (or similar)
- Isolated gate driver: ACPL-332J (optocoupler driver) or transformer/isolated driver module
Power switch:
- MOSFET: choose 600 V class for 400 V bus (part depends heavily on current and switching frequency)
- Add RC snubber + TVS as needed
Safety reality check:
At these voltages, simulation becomes a high-energy power electronics build. Use isolation, creepage/clearance, proper probing, and staged bring-up.
4) Measurement and “simulation credibility”
To claim you are simulating an MCU “max current / high voltage output,” you should measure:
- Load current (shunt + amplifier, or a Hall sensor)
- MOSFET temperature (IR camera / thermocouple)
- Switching waveform (VDS/VCE, gate voltage, ringing)
- Supply dips and transients
Useful current-sense examples (real parts)
- High-side current monitor: INA219 (simple I²C), INA226
- Hall sensor (isolated current): ACS712 / ACS758
5) A simple selection checklist (so you don’t smoke boards)
Define Vload (12/24/48/… V) and Iload (A).
Pick topology:
- low-side MOSFET (default)
- high-side switch (if needed)
- Choose switch ratings:
- VDS ≥ 2× supply (more if inductive/noisy)
- Id ≥ load current with thermal margin
- Add protections:
- flyback diode (inductive)
- fuse
- TVS
- current limit (bench supply or eFuse)
- Validate with a dummy load, then real load.
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