AD7124-8BCPZ-RL7 is a high-precision, low-power, 8-channel, 24-bit sigma-delta (Σ-Δ) analog-to-digital converter (ADC) designed and manufactured by Analog Devices Inc. (ADI). It belongs to the flagship AD7124 family, engineered for industrial process control, precision instrumentation, sensor conditioning, and battery-powered measurement systems, where ultra-low noise, high resolution, channel flexibility, and intelligent on-chip features are critical.
The “BCPZ” suffix denotes the 32-lead LFCSP package (5 mm × 5 mm, 0.5 mm pitch) with exposed thermal pad — optimized for compact layout, low thermal resistance, and excellent high-frequency performance; the “-RL7” indicates 7-inch tape-and-reel packaging (1,500 units per reel), Pb-free, RoHS-compliant, and qualified for industrial operation (–40°C to +125°C junction temperature).
Introduction
The AD7124-8BCPZ-RL7 integrates an exceptionally capable analog front-end in a single chip:
🔹 Eight fully differential or sixteen pseudo-differential input channels, configurable via flexible input multiplexer (MUX);
🔹 24-bit Σ-Δ ADC core with programmable gain (×1 to ×128), selectable output data rate (ODR) from 2.5 SPS to 19.2 kSPS, and true RMS noise as low as 55 nV (at 2.5 SPS, gain = 128) — enabling 21.7 effective number of bits (ENOB) resolution;
🔹 Integrated precision reference (2.5 V, 5 ppm/°C drift) and reference buffer — eliminating external components and reducing system cost/size;
🔹 On-chip digital filtering: sinc4 + post-filter (with adjustable bandwidth), configurable for either high resolution (low ODR) or fast settling (high ODR);
🔹 Intelligent features: per-channel configuration registers, built-in offset/gain calibration, burn-out current sources (for RTD open-wire detection), GPIOs, and CRC error checking.
Crucially, it operates from a single 2.7 V to 3.6 V supply, consuming only 255 µA (typ.) at 2.5 SPS (fully active) and < 1 µA in standby mode, making it ideal for portable, solar-powered, or energy-harvesting sensor nodes. Its LFCSP-32 (BCPZ) package, with exposed pad, achieves θJA ≈ 30°C/W — supporting continuous operation at full channel count even in +85°C ambient environments when properly laid out.
Unlike basic ADCs, the AD7124-8 is a system-on-chip solution: it replaces discrete op-amps, PGA, reference, filter, and calibration circuitry — dramatically simplifying design, improving reliability, and reducing total BOM cost.
Key Features
✅ High Resolution & Ultra-Low Noise:
• Effective resolution: up to 21.7 ENOB @ 2.5 SPS, gain = 128;
• Input-referred noise: 55 nV (rms) @ 2.5 SPS, 125 nV @ 1.2 kSPS;
• INL: ±4 ppm of FSR, DNL: ±0.99 LSB — ensures monotonicity and linearity for precision metrology.
✅ Flexible Input Architecture:
• 8 fully differential inputs or 16 pseudo-differential inputs (using AINCOM as common);
• Programmable gain: ×1, ×2, ×4, ×8, ×16, ×32, ×64, ×128;
• Built-in burn-out current sources (two 500 nA sources) — enables automatic RTD/open-wire fault detection;
• Internal clock (±4% accuracy) or external clock (up to 1 MHz) support.
✅ Integrated Precision Reference & Buffers:
• On-chip 2.5 V reference: 5 ppm/°C max drift, ±0.3% initial accuracy;
• Reference buffer supports rail-to-rail input operation — no external op-amp needed for buffered reference use.
✅ Intelligent On-Chip Processing:
• Per-channel configuration: independent setup for ODR, gain, filter, and input selection — ideal for mixed-sensor systems (e.g., thermocouple + RTD + voltage);
• Auto-calibration (offset/gain) executed in < 50 ms — no host intervention required;
• CRC on all register reads/writes and data output — prevents firmware corruption and communication errors;
• Four general-purpose GPIOs — usable for sensor excitation, status indication, or synchronization.
✅ Low Power & Robust Operation:
• Supply current: 255 µA (typ.) @ 2.5 SPS, 1.2 mA @ 19.2 kSPS;
• Standby current: < 1 µA, wake-up time < 40 µs;
• Operating voltage: 2.7 V to 3.6 V (AVDD/DVDD);
• ESD rating: > 4 kV HBM on all pins;
• Junction temperature range: –40°C to +125°C.
✅ Compact LFCSP-32 (BCPZ) Package:
• 5 mm × 5 mm footprint with 2.5 mm² exposed copper pad;
• Excellent thermal performance and RF immunity;
• RoHS-compliant, halogen-free, and qualified for extended industrial temp range.
Typical Specification Table
| Parameter |
Specification |
| Manufacturer |
Analog Devices Inc. (ADI) |
| Product Series |
AD7124 Family (Precision Low-Power Σ-Δ ADCs) |
| Model |
AD7124-8BCPZ-RL7 |
| Function |
8-Channel, 24-Bit, Low-Power Sigma-Delta ADC |
| Resolution |
24-bit (up to 21.7 ENOB @ 2.5 SPS) |
| Input Channels |
8 fully differential or 16 pseudo-differential |
| Programmable Gain |
×1 to ×128 (8 options) |
| Output Data Rate (ODR) |
2.5 SPS to 19.2 kSPS |
| Input-Referred Noise |
55 nV rms @ 2.5 SPS, gain = 128 |
| INL / DNL |
±4 ppm FSR / ±0.99 LSB |
| Reference |
Integrated 2.5 V (5 ppm/°C drift) |
| Supply Voltage |
2.7 V to 3.6 V (AVDD/DVDD) |
| Supply Current |
255 µA (typ., 2.5 SPS), 1.2 mA (19.2 kSPS) |
| Standby Current |
< 1 µA |
| Operating Temperature |
–40°C to +125°C (junction) |
| Package |
32-Lead LFCSP (5 mm × 5 mm) with Exposed Pad (BCPZ) |
| RoHS / Green |
Yes (Pb-free, Halogen-free) |
| Packaging |
7-inch Reel, 1,500 units (RL7) |
Typical Applications
🔹 Industrial Process Control: PLC analog input modules, flow/pressure/level transmitters, and distributed I/O systems — leveraging 8-channel density, RTD/thermocouple support, and robust noise immunity in noisy factory environments.
🔹 Precision Sensor Conditioning: Strain-gauge bridges (load cells), MEMS accelerometers/gyros, and optical sensors — using low noise, high gain, and built-in burn-out currents for diagnostics.
🔹 Battery-Powered Instrumentation: Handheld multimeters, portable gas detectors, environmental monitors (COâ‚‚, particulate), and wearable health sensors — enabled by sub-250 µA power and 2.7 V operation.
🔹 Medical Devices: Patient monitors (ECG, SpOâ‚‚), infusion pumps, and diagnostic equipment — benefiting from high accuracy, low drift, and integrated safety features (CRC, GPIOs).
🔹 Energy Monitoring & Smart Meters: AC voltage/current sensing (shunt or CT-based), power quality analysis, and tamper detection — using high dynamic range and per-channel configuration.
🔹 Test & Calibration Equipment: Bench-top DMMs, calibrators, and sensor simulators — where 21.7 ENOB and < 5 ppm/°C drift meet Class A metrology requirements.
Development & Design Notes
🔧 PCB Layout Best Practices:
- Use a solid, unbroken ground plane on Layer 2 beneath the BCPZ package — connect the exposed pad (EP) to it with ≥ 16 thermal vias (0.25 mm) in a 4×4 grid.
- Keep analog input traces short, symmetrical, and shielded by ground guard rings tied to AINCOM — essential for achieving < 100 nV noise.
- Route digital (SPI, GPIO) and analog (AINx, REF) sections separately — avoid crossing or parallel routing.
🔧 Power Supply Decoupling:
- Place 10 µF tantalum + 100 nF X7R ceramic capacitors within 2 mm of AVDD and GND pins; add a second 100 nF cap near DVDD/GND.
- Use separate analog (AVDD) and digital (DVDD) supplies — even if both are 3.3 V, decouple them independently and tie grounds at a single point under the IC.
🔧 Reference & Input Optimization:
- For best noise performance, use the internal 2.5 V reference — its low drift and integrated buffer eliminate external component errors.
- If external reference is required (e.g., 4.096 V), drive it into the REFIN(+) pin with a low-noise buffer (e.g., ADA4522) — the internal ref buffer is disabled automatically.
- Enable burn-out currents only when needed (e.g., during RTD startup) — they add ～100 nV noise when active.
🔧 SPI Interface & Firmware Integration:
- Use SPI mode 3 (CPOL = 1, CPHA = 1) at ≤ 1 MHz — the AD7124 supports daisy-chain mode for multiple devices.
- Leverage ADI’s ACE (Analysis, Control, Evaluation) software and evaluation board (EVAL-AD7124-8SDZ) for rapid prototyping and register configuration.
- Implement CRC checking in firmware — read the STATUS register first to verify CRC bit before reading data.
🔧 Calibration & Long-Term Stability:
- Perform one-time factory calibration (offset/gain) at room temperature — the device retains calibration over temperature due to matched on-chip components.
- For metrology-grade applications, perform periodic auto-calibration (every hour or on wake-up) — takes < 50 ms and requires no external equipment.
- MTTF > 1 million hours (per ADI FIT report); no wear-out mechanisms — suitable for 10+ year deployments.
