NIDX-PM-26: Dual-Channel MCU Power Management & Protection Module

NIDX-PM-26 is a dual-channel power distribution, circuit protection, and telemetry module designed by NileDex for microcontrollers (MCUs), development boards (ESP32, STM32, Arduino, Raspberry Pi), and sensitive embedded systems.

The module provides active reverse polarity protection, programmable current-limiting switches with hardware fault flags, and high-precision 20-bit digital power monitoring (voltage, current, power, and energy accumulation) over a shared I2C bus.

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Key Features

• Dual Independent Channels: Two isolated power paths (Channel 1 & Channel 2) capable of operating from independent or common supply rails.
• Active Reverse Polarity Protection: Low-$R_{DS(on)}$ P-Channel MOSFETs (AO3401A) prevent reverse-voltage damage with negligible voltage drop compared to traditional Schottky diodes.
• Precision Electronic Current Limiting & Load Switching: Integrated Texas Instruments TPS2553DBVR power switches with programmable current limit threshold, fast short-circuit response, and thermal shutdown with auto-recovery.
  • Set to ~500 mA per channel ($R_{ILIM} = 47\text{ k}\Omega$), adjustable from 75 mA to 1.7 A by changing resistor values.
• High-Resolution Power Telemetry (INA228): Dual 20-bit Delta-Sigma ADCs monitoring bus voltage, shunt voltage, bidirectional current, and power consumption with high accuracy.
• Hardware Fault & Alert Reporting: Dedicated open-drain FAULT (TPS2553) and programmable ALERT (INA228) outputs broken out for direct microcontroller interrupt handling.
• Flexible Logic Level Compatibility: On-board I2C pull-up resistors are tied to an external VDD_I2C pin, allowing seamless operation with 1.8V, 3.3V, or 5V microcontroller logic.

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System Architecture

                  CHANNEL 1
J1 Pin 1 ──► [Q1: AO3401A] ──► [U1: TPS2553] ──► [R1: 0.1Ω Shunt] ──► J2 Pin 1
 (VIN1)     (Reverse Protect)  (Current Limit)             │          (VOUT1)
                                      │                    ▼
                                      │              [U2: INA228]
                                      ▼             (20-bit I2C: 0x40)
                              FAULT1 ──► J4 Pin 7          │
                                                    ALERT1 ──► J4 Pin 5

                  CHANNEL 2
J1 Pin 2 ──► [Q2: AO3401A] ──► [U4: TPS2553] ──► [R2: 0.1Ω Shunt] ──► J2 Pin 2
 (VIN2)     (Reverse Protect)  (Current Limit)             │          (VOUT2)
                                      │                    ▼
                                      │              [U3: INA228]
                                      ▼             (20-bit I2C: 0x44)
                              FAULT2 ──► J4 Pin 8          │
                                                    ALERT2 ──► J4 Pin 6

                  CONTROL & I2C INTERFACE (J4)
J4 Pin 1 ──► VDD_I2C (Pull-up Reference: 1.8V - 5V)
J4 Pin 2 ──► GND
J4 Pin 3 ──► SDA (Shared I2C Data bus, 4.7kΩ pull-up R3)
J4 Pin 4 ──► SCL (Shared I2C Clock bus, 4.7kΩ pull-up R4)

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Detailed Circuit Design

1. Reverse Polarity Protection (Q1, Q2)

• Part: Alpha & Omega AO3401A (-30V, -4.0A, SOT-23 P-Channel MOSFET).
• Function: Gate tied to GND; Source connects to the circuit rail, and Drain connects to the input power connector.
• Behavior: If reverse voltage is applied ($V_{IN} < 0\text{V}$), $V_{GS} > 0\text{V}$ keeps the MOSFET off, completely blocking reverse current. When correct polarity is applied, the channel turns fully on with $R_{DS(on)} \approx 44\text{ m}\Omega$, minimizing power loss and voltage sag.

2. Overcurrent Protection & Load Switching (U1, U4)

• Part: Texas Instruments TPS2553DBVR (SOT-23-6).
• Operation: Active-high enable (EN) tied to IN for automatic power pass-through.
• Current Limit Programming: The trip current is set by $R_{ILIM}$ resistors R5_LM1 and R6_LM1 ($47\text{ k}\Omega$): $$I_{OS(typ)} \approx \frac{24212}{(R_{ILIM})^{0.985}} \approx \frac{24212}{(47000)^{0.985}} \approx 595\text{ mA}$$ (Nominal continuous working current: $\sim 500\text{ mA}$).
• Fault Detection: The active-low open-drain FAULT pin signals over-current or thermal shutdown events to the host MCU via J4.

3. Precision Current & Power Sensing (U2, U3)

• Part: Texas Instruments INA228 (TSSOP-10).

• Resolution: 20-bit Delta-Sigma ADC with $1\text{ }\mu\text{V}$ shunt voltage LSB and $195.3125\text{ }\mu\text{V}$ bus voltage LSB.

• Current Sense Resistors: R1, R2 = $0.1\text{ }\Omega$ ($100\text{ m}\Omega$, 0805 SMD package).

• I2C Addressing:

  Channel	IC Designator	A1 Pin	A0 Pin	7-bit I2C Address (Hex)	7-bit I2C Address (Binary)
  Ch 1	U2	GND	GND	0x40	1000000b
  Ch 2	U3	VS (Rail)	GND	0x44	1000100b

• Alert Pins: Open-drain output asserted when programmed power, current, or voltage limits are exceeded.

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Connector Pinouts

J1: Input Power Connector (1x03 Pin Header, 1.00mm Pitch)

Pin #	Silkscreen	Signal	Type	Description
1	+5v	VIN1	Power Input	Channel 1 Input Voltage (+2.5V to +6.5V)
2	3v3	VIN2	Power Input	Channel 2 Input Voltage (+2.5V to +6.5V)
3	GND	GND	Ground	Common Power Ground

J2: Output Power Connector (1x03 Pin Header, 1.00mm Pitch)

Pin #	Silkscreen	Signal	Type	Description
1	+5v	VOUT1	Power Output	Channel 1 Protected & Monitored Power Output
2	3v3	VOUT2	Power Output	Channel 2 Protected & Monitored Power Output
3	GND	GND	Ground	Common Power Ground

J4: Telemetry & Diagnostics Interface (1x08 Pin Header, 1.00mm Pitch)

Pin #	Silkscreen	Signal	Type	Description
1	VIO	VDD_I2C	Power Input	I2C pull-up reference voltage (1.8V, 3.3V, or 5V MCU logic)
2	GND	GND	Ground	System Ground reference for digital signals
3	SDA	SDA	I/O	I2C Data line (pulled up via R3 $4.7\text{ k}\Omega$ to VIO)
4	SCL	SCL	Input	I2C Clock line (pulled up via R4 $4.7\text{ k}\Omega$ to VIO)
5	ALRT	ALERT1	Output (OD)	Channel 1 INA228 programmable threshold alert
6	ALRT	ALERT2	Output (OD)	Channel 2 INA228 programmable threshold alert
7	FAULT	FAULT1	Output (OD)	Channel 1 TPS2553 fault flag (Active Low)
8	FAULT	FAULT2	Output (OD)	Channel 2 TPS2553 fault flag (Active Low)

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Electrical Specifications

Parameter	Min	Typical	Max	Unit	Notes
Input Voltage ($V_{IN}$)	2.5	3.3 / 5.0	6.5	V	Limited by TPS2553 supply range
Current Limit Threshold ($I_{LIMIT}$)	450	500	600	mA	Configured by $47\text{ k}\Omega$ $R_{ILIM}$ resistors
Current Sense Resistance ($R_{SHUNT}$)	-	0.1	-	$\Omega$	Tolerance 1%, 0805 package
Reverse Polarity Voltage Blocking	-	-	-30	V	$V_{DS(max)}$ of AO3401A
I2C Bus Speed	10	400	1000	kHz	Standard, Fast, and Fast-Mode+ supported
Digital Logic Voltage (VDD_I2C)	1.8	3.3	5.5	V	Feeds pull-ups R3 and R4
Operating Ambient Temperature	-40	+25	+85	°C	Industrial rated components

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Bill of Materials (BOM)

Designator	Value / Part Number	Description	Footprint / Package
U1, U4	TPS2553DBVR	Precision Adj. Current-Limited Switch	SOT-23-6
U2, U3	INA228	20-bit Current/Power/Energy Monitor	TSSOP-10 (3x3mm, 0.5mm pitch)
Q1, Q2	AO3401A	P-Channel MOSFET (-30V, -4.0A)	SOT-23-3
R1, R2	0.1 ($100\text{ m}\Omega$)	Current Shunt Resistor, 1%	SMD 0805
R3, R4	4.7k	I2C Bus Pull-Up Resistors	SMD 0805
R5_LM1, R6_LM1	47k	Current Limit Set Resistors (TPS2553)	SMD 0805
C1, C2, C3, C4	100n ($0.1\text{ }\mu\text{F}$)	Ceramic Decoupling Capacitors, 50V	SMD 0805
C5, C6, C7, C8	10u ($10\text{ }\mu\text{F}$)	Ceramic Bulk Filter Capacitors, 16V/25V	SMD 0805
J1, J2	Conn_01x03	3-pin Power Input/Output Header	1x03 Pin Header (1.00mm pitch)
J4	Conn_01x08	8-pin Diagnostics & Telemetry Header	1x08 Pin Header (1.00mm pitch)

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Firmware Integration Example (Arduino / C++)

#include <Wire.h>

// I2C Addresses
#define INA228_CH1_ADDR 0x40
#define INA228_CH2_ADDR 0x44

// Pin Definitions on Host MCU
#define PIN_FAULT1 4
#define PIN_FAULT2 5
#define PIN_ALERT1 6
#define PIN_ALERT2 7

void setup() {
  Serial.begin(115200);
  Wire.begin();

  pinMode(PIN_FAULT1, INPUT_PULLUP);
  pinMode(PIN_FAULT2, INPUT_PULLUP);
  pinMode(PIN_ALERT1, INPUT_PULLUP);
  pinMode(PIN_ALERT2, INPUT_PULLUP);

  Serial.println("NIDX-PM-26 Initialized.");
}

void loop() {
  // Check for TPS2553 hardware fault (Active LOW)
  if (digitalRead(PIN_FAULT1) == LOW) {
    Serial.println("WARNING: Channel 1 Over-Current or Thermal Fault detected!");
  }
  if (digitalRead(PIN_FAULT2) == LOW) {
    Serial.println("WARNING: Channel 2 Over-Current or Thermal Fault detected!");
  }

  // Read voltage & current telemetry via I2C (INA228)
  readTelemetry(INA228_CH1_ADDR, "Channel 1");
  readTelemetry(INA228_CH2_ADDR, "Channel 2");

  delay(1000);
}

void readTelemetry(uint8_t address, const char* channelName) {
  // Read VBUS Register (0x05 for INA228)
  Wire.beginTransmission(address);
  Wire.write(0x05);
  if (Wire.endTransmission() == 0) {
    Wire.requestFrom(address, (uint8_t)3);
    if (Wire.available() >= 3) {
      uint32_t rawVbus = ((uint32_t)Wire.read() << 16) | ((uint32_t)Wire.read() << 8) | Wire.read();
      rawVbus >>= 4; // 20-bit data alignment
      float voltage = rawVbus * 195.3125e-6; // 195.3125 uV/LSB
      Serial.print(channelName);
      Serial.print(" Voltage: ");
      Serial.print(voltage, 3);
      Serial.println(" V");
    }
  }
}

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Repository Structure

mcu-protection/
├── .gitignore                     # Git ignore rules (schematics, netlists & temporary files ignored)
├── LICENSE                        # MIT License
├── README.md                      # Hardware documentation and wiring guide
├── mcu-protection.kicad_pro       # KiCad 10 project file
├── mcu-protection.kicad_pcb       # KiCad PCB layout
├── mcu-protection.png             # PCB 3D preview render
└── ERC.rpt                        # Electrical Rules Check report

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License

This project is licensed under the MIT License. Copyright (c) 2026 NileDex (NIDX-PM-26 Contributors).