Adafruit LM73100 Ideal Diode Breakout

Ideal for your power budget

by Liz Clark

published July 16, 2025, last edited July 16, 2025

posted in Adafruit Products Arduino Compatibles CircuitPython Breakout Boards/ Batteries/Power

Beginner

Product guide

Arduino

Using the LM73100 Ideal Diode with Arduino involves wiring up the breakout to your Arduino-compatible microcontroller and running the provided example code.

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Wiring

Wire as shown for a 5V board like an Uno, with the breakout inline with an external DC power supply. If you are using a 3V board, like an Adafruit Feather, wire the board's 3V pin to the breakout VIN.

Power supply positive to ideal diode VIN (red wire)
Power supply negative to ideal diode GND (black wire)
Ideal diode OUT to DC jack positive (red wire)
Ideal diode GND to DC jack negative (black wire)
DC jack output to Metro DC jack
Ideal diode IMON to Metro pin A0 (yellow wire)

No additional libraries are needed for this example.

Example Code

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// SPDX-FileCopyrightText: 2025 Liz Clark for Adafruit Industries
//
// SPDX-License-Identifier: MIT

// LM73100 IMON Current Monitoring

const int IMON_PIN = A0;           // IMON connected to analog pin A0
const float RIMON = 1500.0;        // RIMON resistor value in ohms (1.5kΩ)
const float GIMON = 2.5;           // GIMON typical value in μA/A (from datasheet, typical is 2.5)
const float VREF = 5.0;            // Arduino reference voltage (5V for most Arduinos)
const int ADC_RESOLUTION = 1024;

void setup() {
  Serial.begin(9600);
  pinMode(IMON_PIN, INPUT);
  
  Serial.println("LM73100 Current Monitor Started");
  Serial.println("================================");
  Serial.print("RIMON: ");
  Serial.print(RIMON);
  Serial.println(" ohms");
  Serial.print("GIMON: ");
  Serial.print(GIMON);
  Serial.println(" μA/A");
  Serial.println("================================\n");
}

void loop() {
  int adcValue = analogRead(IMON_PIN);
  float vimon = (adcValue * VREF) / ADC_RESOLUTION;
  float iout_A = vimon / (RIMON * GIMON);
  float iout_mA = iout_A * 1000.0;

  Serial.print("ADC Value: ");
  Serial.print(adcValue);
  Serial.print(" | VIMON: ");
  Serial.print(vimon, 3);
  Serial.print(" V | Output Current: ");
  Serial.print(iout_mA, 2);
  Serial.print(" mA (");
  Serial.print(iout_A, 3);
  Serial.println(" A)");
  
  delay(500);  // Read every 500ms
}

// SPDX-FileCopyrightText: 2025 Liz Clark for Adafruit Industries
//
// SPDX-License-Identifier: MIT

// LM73100 IMON Current Monitoring

const int IMON_PIN = A0;           // IMON connected to analog pin A0
const float RIMON = 1500.0;        // RIMON resistor value in ohms (1.5kΩ)
const float GIMON = 2.5;           // GIMON typical value in μA/A (from datasheet, typical is 2.5)
const float VREF = 5.0;            // Arduino reference voltage (5V for most Arduinos)
const int ADC_RESOLUTION = 1024;

void setup() {
  Serial.begin(9600);
  pinMode(IMON_PIN, INPUT);
  
  Serial.println("LM73100 Current Monitor Started");
  Serial.println("================================");
  Serial.print("RIMON: ");
  Serial.print(RIMON);
  Serial.println(" ohms");
  Serial.print("GIMON: ");
  Serial.print(GIMON);
  Serial.println(" μA/A");
  Serial.println("================================\n");
}

void loop() {
  int adcValue = analogRead(IMON_PIN);
  float vimon = (adcValue * VREF) / ADC_RESOLUTION;
  float iout_A = vimon / (RIMON * GIMON);
  float iout_mA = iout_A * 1000.0;

  Serial.print("ADC Value: ");
  Serial.print(adcValue);
  Serial.print(" | VIMON: ");
  Serial.print(vimon, 3);
  Serial.print(" V | Output Current: ");
  Serial.print(iout_mA, 2);
  Serial.print(" mA (");
  Serial.print(iout_A, 3);
  Serial.println(" A)");
  
  delay(500);  // Read every 500ms
}

Upload the sketch to your board and open up the Serial Monitor (Tools -> Serial Monitor) at 115200 baud. You'll see the raw analog reading, the IMON voltage reading and the current draw from the IMON pin printed out to the Serial Monitor. The code uses the formula from the datasheet (page 20, section 7.3.5 "Analog Load Current Monitor Output"):

Iout (A) = (Vimon(V) × 10^-6) / (Rimon(Ω) × Gimon(μA/A))

to calculate the current from the voltage output from the IMON pin as an analog reading.

Page last edited July 15, 2025