Overview

The AD8232 is an integrated signal conditioning block for electrocardiogram (ECG / EKG) and other biopotential measurement applications manufactured by Analog Devices. It is designed to extract, amplify, and filter small biopotential electrical signals (∼1 mV\sim 1\text{ mV}) generated by the heart in the presence of noisy motion artifacts or electrode placement noise.

The module features a high Common-Mode Rejection Ratio (CMRR = 80 dB), a built-in Right Leg Drive (RLD) amplifier, fast restore circuitry, and an integrated Leads-Off Detection circuit (LO+ and LO-) that alerts the microcontroller if an electrode becomes disconnected from the subject's body.

Quick reference

Operating voltage (VCC)2.0 V to 3.5 V DC (3.3 V nominal)
Supply current170 µA typical
Instrumentation amplifier gain100 V/V (fixed internal high-gain stage)
Common-Mode Rejection Ratio (CMRR)80 dB (dc to 60 Hz)
High-Pass Filter2-pole adjustable high-pass filter (typically set to 0.5 Hz)
Low-Pass Filter3-pole adjustable low-pass filter (typically set to 40 Hz)
Leads-Off DetectionBuilt-in AC/DC leads-off detection (LO+, LO-)
Output interfaceAnalog voltage signal (OUTPUT)

Pinout

Standard 6-Pin Breakout Header & 3.5mm Electrode Jack

Pin / JackNameTypeDescription
3.5mm JackLA, RA, RLElectrode InputsConnects to 3-lead biomedical electrode cable (Left Arm, Right Arm, Right Leg)
Header Pin 1GNDPowerGround (0 V)
Header Pin 23.3V / VCCPowerSupply voltage (+2.0 V to +3.5 V DC, 3.3V recommended)
Header Pin 3OUTPUTAnalog OutputConditioned analog ECG signal (center-biased at VCC/2V_{CC} / 2)
Header Pin 4LO-Digital OutputLeads-Off indicator Minus (HIGH = Left Arm electrode disconnected)
Header Pin 5LO+Digital OutputLeads-Off indicator Plus (HIGH = Right Arm electrode disconnected)
Header Pin 6SDN / PWRDigital InputShutdown pin (LOW = Shutdown mode 0.5µA, HIGH = Normal operation)

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply VoltageVSV_{S}2.03.33.5VDC
Quiescent CurrentISYI_{SY}—170250µANormal operation
Shutdown CurrentISDNI_{SDN}—0.52.0µASDN=LOWSDN = LOW
Common-Mode Rejection RatioCMRRCMRR7480—dBdc to 60 Hz
High-Pass Filter FrequencyfHPf_{HP}—0.5—Hz2-pole active filter
Low-Pass Filter FrequencyfLPf_{LP}—40—Hz3-pole active filter
Analog Output Voltage RangeVOUTV_{OUT}0.1VCC/2V_{CC}/2VCC−0.1V_{CC}-0.1VBiased at mid-supply (1.65 V1.65\text{ V})

Electrode Placement (3-Lead Configuration)

For clean Cardiac Electrocardiogram (ECG) recording:

text
          [ RA ] ── Right Clavicle / Chest
          [ LA ] ── Left Clavicle / Chest
          [ RL ] ── Right Lower Abdomen / Leg (Driven Ground)
  • RA (Red - Right Arm): Place below the right collarbone or right arm.
  • LA (Black - Left Arm): Place below the left collarbone or left arm.
  • RL (Green - Right Leg): Place on the right lower abdomen or right leg (acts as Right Leg Drive for active noise cancellation).

Wiring

AD8232 Breakout Pin→Microcontroller (Arduino Uno / ESP32)Notes
3.3V / VCC3.3VDo NOT connect to 5V!
GNDGNDGround
OUTPUTAnalog Pin A0 (or ESP32 ADC)Conditioned ECG signal
LO+Digital Pin D10Leads-Off status check
LO-Digital Pin D11Leads-Off status check
SDN3.3V (or GPIO Pin)Must be pulled HIGH to enable module
Warning

Medical Safety Warning & Maximum Voltage:

  • The AD8232 is an educational/hobbyist sensor. It is NOT a certified medical device and must never be used for medical diagnosis, treatment, or life-support applications.
  • Power Supply Voltage limit: Maximum supply voltage is 3.5 V DC. Supplying 5.0 V directly to VCC will destroy the AD8232 IC.

Common mistakes

  • Powering from 5.0V: Exceeding 3.5V causes permanent IC failure.
  • Ignoring Leads-Off outputs: When electrodes are not attached to skin, OUTPUT produces wild random noise. Check if (digitalRead(LO_PLUS) || digitalRead(LO_MINUS)) in code to ignore invalid readings.
  • Placing electrodes over muscle groups: Placing electrodes over large active muscles (e.g. biceps/thighs) introduces electromyogram (EMG) muscle noise artifacts. Place electrodes over bony chest areas.

Notes

  • Signal processing software (such as a Pan-Tompkins algorithm) can detect QRS complexes in the analog output stream to calculate heart rate in Beats Per Minute (BPM).

Assets & downloads