AD7691BCPZ - 18-Bit 250kSPS Differential ADC | Analog Devices
MPN: AD7691BCPZ ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $20.45 | $20.45 |
| 10 | $18.5 | $185.00 |
| 100 | $16.2 | $1,620.00 |
| 500 | $14.8 | $7,400.00 |
| 1,000 | $13.5 | $13,500.00 |
AD7691BCPZ Overview
An ADC (analog-to-digital converter) is an electronic component that converts continuous analog signals into discrete digital codes for processing by digital systems. The AD7691 is a SAR ADC, which uses a binary search algorithm to approximate the input voltage with high speed and low power. SAR ADCs are widely used in data acquisition systems, industrial process control, and medical instrumentation due to their excellent balance of speed, resolution, and power consumption.
Key features of the AD7691BCPZ include a 250 kSPS throughput, 18-bit resolution, and a pseudo-differential input that can be configured for true differential operation. The SPI-compatible serial interface supports daisy-chaining multiple ADCs on a single 3-wire bus using the SDI input, and provides an optional busy indicator. The device also features a track-and-hold amplifier with a 1 MHz full-power bandwidth, making it suitable for high-frequency signal acquisition.
The AD7691 uses a charge redistribution SAR architecture with an internal reference buffer, achieving a signal-to-noise ratio (SNR) of 101 dB and a total harmonic distortion (THD) of -118 dB at 1 kHz. The device operates over the industrial temperature range of -40°C to +85°C and is available in both MSOP and LFCSP packages. The LFCSP package (CPZ suffix) offers a compact footprint for space-constrained designs.
Typical applications include battery-powered instruments, data acquisition systems, industrial process control, medical instrumentation, and seismic data acquisition. The high resolution and low noise make it ideal for precision sensor interfaces and vibration analysis.
When designing with the AD7691, ensure proper decoupling of the AVDD and DVDD supplies with 10 µF and 0.1 µF capacitors placed close to the pins. The reference input should be driven by a low-impedance source, and the VIO supply must be matched to the host logic level to avoid interface damage.
Drop-in alternatives for AD7691BCPZ — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with AD7691BCPZ (same form factor and footprint) — differing in Resolution, Sampling Rate, Input Type, Data Interface, INL (Max).
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
AD7691BCPZ-R2
✅ Drop-In📋 Reference alternative (not in catalog)
AD7980BCPZ-RL7
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$18 / Unit
View Datasheet →AD7690BCPZRL7
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$17.6 / Unit
View Datasheet →AD7691BCPZ Maximum Ratings & Electrical Characteristics
| Resolution | 18 bit |
| Sampling Rate | 250 kSPS |
| Input Type | Differential |
| Number of Inputs | 1 |
| Architecture | SAR |
| INL (Max) | 1.5 LSB |
| SNR (Typ) | 101 dB |
| THD (Typ) | -118 dB |
| Supply Voltage | 2.3 V to 5.5 V |
| Logic Supply Voltage (VIO) | 1.8 V to 5 V |
| Operating Temperature | -40°C to +85°C |
| Package | 10-Lead LFCSP-WD (3x3 mm) |
| Mounting Type | Surface Mount |
| Interface | SPI, Daisy-Chain |
| RoHS Status | Compliant |
AD7691BCPZ Pin Configuration
| Pin 1 | IN+ — Positive analog input |
| Pin 2 | IN- — Negative analog input |
| Pin 3 | GND — Ground |
| Pin 4 | VIO — Logic supply voltage |
| Pin 5 | SCK — Serial clock input |
| Pin 6 | SDI — Serial data input for daisy-chain |
| Pin 7 | SDO — Serial data output |
| Pin 8 | CNV — Convert input |
| Pin 9 | DVDD — Digital supply voltage |
| Pin 10 | AVDD — Analog supply voltage |
Typical Applications
AD7691BCPZ is suitable for 6 applications: Battery-Powered Instruments, Data Acquisition Systems, Industrial Process Control, Medical Instrumentation, Seismic Data Acquisition, Precision Sensor Interfaces.
Battery-Powered Instruments
The AD7691BCPZ's low power consumption (typically 7.5 mW at 250 kSPS) and wide supply range (2.3 V to 5.5 V) make it ideal for portable battery-powered instruments. Its 18-bit resolution ensures accurate measurement of sensor signals while extending battery life. The device can be powered directly from a 3.3 V battery and interfaces with low-voltage microcontrollers via the VIO pin.
Recommended
Data Acquisition Systems
In multi-channel data acquisition systems, the AD7691BCPZ provides high accuracy and speed with a differential input that rejects common-mode noise. Its SPI interface supports daisy-chaining, allowing multiple ADCs to share a single bus, reducing wiring complexity. The 250 kSPS throughput is sufficient for most industrial sensors, and the 18-bit resolution captures fine signal details.
Recommended
Industrial Process Control
The AD7691BCPZ is well-suited for industrial process control loops that require precise monitoring of temperature, pressure, and flow. Its 1.5 LSB INL ensures accurate conversion, and the differential input rejects interference from motors and other industrial equipment. The device operates over -40°C to +85°C, making it reliable in harsh environments.
Recommended
Medical Instrumentation
In medical devices such as patient monitors and diagnostic equipment, the AD7691BCPZ provides the high resolution and low noise required for accurate biosignal acquisition. Its small LFCSP package saves board space, and the low power consumption is critical for battery-operated devices. The SPI interface simplifies connection to medical-grade microcontrollers.
Recommended
Seismic Data Acquisition
Seismic sensors produce low-frequency signals with wide dynamic range, requiring high-resolution ADCs. The AD7691BCPZ's 18-bit resolution and 101 dB SNR capture subtle ground movements. Its differential input rejects common-mode noise from long cable runs, and the 250 kSPS rate is sufficient for seismic frequencies. The device's low power is advantageous for remote sensing nodes.
Recommended
Precision Sensor Interfaces
The AD7691BCPZ is ideal for precision sensor interfaces in test and measurement equipment. Its 18-bit resolution and low INL ensure accurate conversion of sensor outputs, while the differential input allows direct connection to bridge sensors and thermocouples. The SPI interface with daisy-chain capability simplifies system design, and the wide supply range accommodates various power rails.
Recommended
Recommended Products Summary
Engineering reference data for AD7691BCPZ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AD7691BCPZ-R2 | AD7690BRMZ | AD7980BCPZ |
|---|---|---|---|---|
| Package | 10-Lead LFCSP-WD (3x3 mm) | 10-Lead LFCSP-WD (3x3 mm) | 10-Lead MSOP | 10-Lead LFCSP-WD (3x3 mm) |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Resolution | 18 bit | 18 bit | 18 bit | 16 bit |
| Sampling Rate | 250 kSPS | 250 kSPS | 250 kSPS | 1 MSPS |
| Input Type | Differential | Differential | Differential | Differential |
| INL (Max) | 1.5 LSB | 1.5 LSB | 2 LSB | 1.5 LSB |
| SNR (Typ) | 101 dB | 101 dB | 101 dB | 91.5 dB |
| Supply Voltage | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 2.3 V to 5.5 V |
Key Differentiators
- Higher resolution than AD7980BCPZ (vs AD7980BCPZ)
- Lower INL than AD7690BRMZ (vs AD7690BRMZ)
- Differential input with high SNR (vs AD7980BCPZ)
Design Notes
Decouple the AVDD and DVDD pins with 10 µF and 0.1 µF capacitors placed as close as possible to the device. Use a low-impedance ground plane to minimize noise. The VIO pin should be decoupled with a 0.1 µF capacitor and connected to the same supply as the host logic to ensure proper interface levels.
For optimal performance, route the analog input traces as a differential pair with equal length and keep them away from digital signals. Use a solid ground plane under the ADC and avoid routing digital lines beneath the analog input area. The reference input should be driven by a low-impedance source, and a 10 µF capacitor should be placed at the REF pin.
Ensure the input signal is within the specified common-mode range and does not exceed the supply rails. The CNV pin must be pulsed to initiate a conversion; leaving it low will not trigger conversions. When daisy-chaining, ensure the SDI of the last device is tied to ground to avoid data corruption.
Compliance Information
RoHS compliant per Analog Devices product page. No AEC-Q100 qualification indicated for this part.
