AD8232

Both are single-lead biopotential front ends in the same 20-lead LFCSP footprint, but the AD8233 is optimised for lower power and slightly different filter flexibility, drawing less supply current than the AD8232's 170 µA typical, while the AD8232 offers the more widely documented filter topology, fast restore and AC/DC lead-off options that most reference designs are built around. Evaluate both against your battery budget; most fitness products stay with the AD8232 because the reference designs and evaluation boards are abundant.

You can, but you inherit four problems the AD8232 solves on-chip: electrode half-cell potentials of ±300 mV that would saturate a DC-coupled amplifier, the need for a high-pass stage before large gain, common-mode drive from mains that requires a driven-right-leg circuit, and lead-off detection. Replicating all of that discretely costs more board area, more quiescent current and more layout risk than the integrated part. Use a discrete instrumentation amplifier when you need programmable gain, a wider bandwidth or a measurement that is not a biopotential.

The two-pole high-pass corner is set by external components on HPSENSE and HPDRIVE: for monitoring-grade ECG keep it around 0.5 Hz so the ST segment survives, and for heart-rate-only applications you can push it to 5 Hz to 8 Hz to kill motion artefact at the cost of waveform fidelity. The three-pole low-pass is built with the uncommitted op-amp on OPAMP+, OPAMP- and IAOUT — set it to roughly 40 Hz for heart rate, or 100 Hz to 150 Hz if you need QRS morphology. Then sample at 250 Hz to 500 Hz. Note that raising the high-pass corner makes the fast-restore feature less critical, since railing events recover sooner.

The AC/DC pin selects between injecting a small AC current into the electrode and applying DC currents. In both cases, when an electrode disconnects the input bias path opens, the amplifier rails, and the LOD+ and LOD- pins indicate the condition; fast restore then shortens the recovery when the electrode is reattached. Use AC mode for battery-powered wearables where power and electrode polarisation matter, and DC mode where you want simpler, faster detection with dry electrodes. Test the behaviour on your own electrode and cable set, because lead-off thresholds depend on skin impedance.

Only as part of a properly engineered system. The AD8232 is a component with no galvanic isolation, so a patient-connected diagnostic device still needs isolation barriers, limited patient leakage current, protection against defibrillator and electrosurgical voltages, and compliance with IEC 60601-1 and IEC 60601-2-27 (or your regional equivalents). It is well suited to fitness, well-being and single-lead personal monitoring products, which is where the vast majority of its designs live. Do not connect a subject to a mains-powered prototype without isolation and a safety review.

Work through the chain. Confirm the RLD amplifier is actually driving the third electrode — without a driven reference, common-mode rejection collapses. Check electrode contact and skin preparation, since dry or loosely attached electrodes produce large, drifting half-cell potentials. Verify the reference buffer capacitor and that REFOUT is not loaded. Keep input traces short, symmetrical and away from the switching regulator and the display; add a guard ring tied to the reference. Then confirm the low-pass corner: a three-pole filter at 40 Hz only gives about 5 dB at 50 Hz, so it supplements proper common-mode drive and layout rather than replacing them.

Measure, do not just look. At 3 V the genuine part draws about 170 µA; clones often draw several times that or almost nothing. Check that REFOUT sources a stable reference, that the instrumentation stage produces a gain of about 100 with an input shorted and a small AC test signal applied, and that lead-off detection asserts when you disconnect an electrode. Physically, verify the 20-lead 4 mm × 4 mm LFCSP outline with an exposed thermal pad, crisp laser marking and a date code traceable to Analog Devices. Counterfeit parts are common on the breakout-board market, so buy the bare IC through an authorized channel when the product is going to patients.

MOQ is 1 reel of AD8232ACPZ-R7 (1,500 pcs, 20-lead LFCSP) for production, or 50 pcs loose for prototyping and small batches. ADI authorized channel lead time is typically 10-16 weeks; our Shenzhen stock ships in 1-3 business days. We can supply lot traceability, a certificate of conformance and reel photos before dispatch.