AD7685CCPZ-R2 - 16-Bit 250 kSPS SAR ADC | Analog Devices | LFCSP-10
MPN: AD7685CCPZ-R2 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $8.95 | $8.95 |
| 10 | $7.96 | $79.60 |
| 100 | $6.45 | $645.00 |
| 500 | $5.5 | $2,750.00 |
| 1,000 | $4.85 | $4,850.00 |
| 2,500 | $4.2 | $10,500.00 |
AD7685CCPZ-R2 Overview
A SAR ADC (Successive Approximation Register Analog-to-Digital Converter) is a precision data converter architecture that resolves one bit per clock cycle by switching a charge-redistribution capacitor DAC against the input signal. The SAR architecture is the de-facto choice for applications requiring low latency, deterministic acquisition, and excellent DC accuracy at moderate sampling rates; it sits hierarchically under ADC -> data converter -> signal chain IC -> semiconductor. Compared to delta-sigma converters, SAR ADCs deliver faster settling with no digital decimation delay.
Key features of the AD7685 include 16-bit resolution with no missing codes, true differential analog input, SPI/QSPI/MICROWIRE/DSP-compatible serial interface, and a low 4 mW typical power dissipation at 250 kSPS with 5 V supply. The internal oscillator and reference buffer remove the need for external clock or buffer components, enabling compact BOM-precision or data acquisition front ends. The wide 2.3 V-5.5 V supply range supports both 3.3 V and 5 V system rails.
Architecturally, the AD7685 uses a charge-redistribution switched-capacitor DAC core with inherent sample-and-hold, followed by a precision successive-approximation register and digital error correction. The LFCSP-WD-10 (3x3) package provides a thermal pad that must be soldered to the PCB ground plane to achieve the rated AC and DC performance, since the die pad is the primary thermal and electrical return.
Typical applications include industrial process control (4-20 mA loop digitization), portable instrumentation and battery-powered data loggers, precision sensor signal conditioning, and medical monitoring front ends. When designing with the AD7685, ensure the exposed pad is soldered to a grounded copper pour of at least 10 mm^2; missing this connection degrades linearity. Use short, symmetric analog input traces and place the reference decoupling capacitor within 5 mm of the REF pin to preserve 16-bit performance.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet, giving engineers a single-source reference for selecting the AD7685CCPZ-R2 in precision data-acquisition designs.
Drop-in alternatives for AD7685CCPZ-R2 — 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 AD7685CCPZ-R2 (same form factor and footprint) — differing in Architecture, Package, Number of Channels, Resolution, Input Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
AD7685BCPZ-R2
✅ Drop-In📋 Reference alternative (not in catalog)
AD7685CCPZ
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
AD7686BCPZ-R2
✅ Drop-In✓ In Stock
$6.8 / Unit
View Datasheet →AD7687BCPZ-R2
✅ Drop-In✓ In Stock
$6.85 / Unit
View Datasheet →AD7942BCPZ-R2
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
AD7680ACPZ-R2
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
AD7685CCPZ-R2 Maximum Ratings & Electrical Characteristics
| Resolution | 16 Bit |
| Architecture | SAR (Successive Approximation Register) |
| Sampling Rate | 250 kSPS |
| Number of Channels | 1 |
| Input Type | Differential (Pseudo) |
| Supply Voltage (VDD) | 2.3 V to 5.5 V |
| Digital Interface | SPI / QSPI / MICROWIRE / DSP compatible |
| Package | 10-LFCSP-WD (3x3) with exposed pad |
| No Missing Codes | 16-bit guaranteed |
| Internal Conversion Clock | Yes |
| RoHS Status | Compliant |
| Mounting Type | Surface Mount |
AD7685CCPZ-R2 Pin Configuration
| Pin 1 | VDD — Power supply input, 2.3 V to 5.5 V |
| Pin 2 | IN+ — Positive differential analog input |
| Pin 3 | IN- — Negative differential analog input |
| Pin 4 | EP (Exposed Pad) — Thermal and electrical ground; MUST be soldered to PCB ground pour |
| Pin 5 | GND — Ground reference |
| Pin 6 | REF — Reference voltage input / output (decouple with 10 uF) |
| Pin 7 | CNV — Conversion start input (active low or edge-triggered per datasheet) |
| Pin 8 | SDO — Serial data output (SPI MISO) |
| Pin 9 | SCK — Serial clock input (SPI SCLK) |
| Pin 10 | SDI — Serial data input (SPI MOSI / daisy-chain) |
Typical Applications
AD7685CCPZ-R2 is suitable for 6 applications: Industrial Process Control / PLC Analog Input, Portable Battery-Powered Data Loggers, Precision Sensor Signal Conditioning, Medical Monitoring Equipment, Automotive Sensor Digitization, Test and Measurement Instrumentation.
Industrial Process Control / PLC Analog Input
The AD7685CCPZ-R2 fits industrial PLC analog input modules because its 16-bit no-missing-codes performance and 250 kSPS throughput reliably digitize 4-20 mA loop signals, thermocouple, and RTD-conditioned outputs. With a single 2.3 V-5.5 V supply and 4 mW typical power dissipation, it slots directly into modular backplanes powered from 24 V industrial rails via local regulation. The pseudo-differential input simplifies PCB routing for multi-channel modules, while the SPI-compatible digital interface enables direct connection to M-series FPGA SoCs such as Xilinx Xilinx XC7S25 or Xilinx XC6SLX9 for deterministic cyclic sampling at 250 kSPS.
Recommended
Portable Battery-Powered Data Loggers
The AD7685CCPZ-R2 is well suited for portable, battery-powered data loggers measuring temperature, strain, or pressure sensors. Its 4 mW typical power at 250 kSPS from a 5 V supply translates to 50+ hours of continuous logging on a small Li-ion cell, while the 2.3 V lower bound allows direct operation from 2xAA batteries without boost conversion. The exposed-pad LFCSP-WD-10 (3x3) package occupies just 9 mm^2 of PCB area, enabling wearable-grade form factors. Pair with a low-noise LDO such as TPS7A4701 and a Cortex-M0 MCU for a complete precision logger reference design.
Recommended
Precision Sensor Signal Conditioning
For precision sensor signal conditioning front ends, the AD7685CCPZ-R2 delivers the 16-bit dynamic range needed to digitize strain gauge bridges, weigh scales, and pressure transducers directly. Its true-differential input rejects common-mode noise from long sensor leads, while the internal reference buffer simplifies the analog front end to just one external decoupling capacitor. The 250 kSPS sampling rate is overkill for static weighing but enables simultaneous temperature compensation through multiplexed auxiliary channels. Use with an instrumentation amplifier like the AD8421 for full-bridge strain gauge applications.
Recommended
Medical Monitoring Equipment
In medical monitoring equipment such as patient vital-sign monitors and infusion pumps, the AD7685CCPZ-R2 provides the 16-bit accuracy required to resolve microvolt-level bioelectric signals including ECG, EEG, and EMG. Its low 4 mW power dissipation supports battery-powered portable monitors that must run for days on a single charge. The SPI-compatible interface integrates with medical-grade MCUs and DSPs for real-time waveform analysis. Combined with proper IEC 60601 isolation barriers, the AD7685 forms the core of a 16-channel patient monitoring acquisition front end.
Recommended
Automotive Sensor Digitization
For automotive sensor digitization including pedal position, throttle body, and HVAC temperature sensing, the AD7685CCPZ-R2's wide -40C to +85C operating range covers the automotive Grade 2 environment. Its pseudo-differential analog input rejects ground-shift noise common in long cable harnesses. The 250 kSPS throughput supports high-speed applications such as airbag crash sensor conditioning and battery management current sensing. Note that AEC-Q100 qualification is not explicitly stated for this part number; for AEC-Q100-qualified PulSAR equivalents, contact Analog Devices automotive line.
Recommended
Test and Measurement Instrumentation
The AD7685CCPZ-R2 is ideal for handheld multimeters, oscilloscope front ends, and bench-top data acquisition systems where 16-bit precision and 250 kSPS bandwidth enable accurate capture of slowly varying signals. Its compact 3x3 mm LFCSP-WD package fits inside slim meter form factors while the SPI interface allows direct connection to display MCUs. The pseudo-differential input handles ground-referenced thermocouple and current-shunt measurements without external instrumentation amplifiers in many cases, reducing BOM cost and PCB area for portable T&M products.
Recommended
Recommended Products Summary
Engineering reference data for AD7685CCPZ-R2 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AD7685BCPZ-R2 | AD7685CCPZ | AD7686BCPZ-R2 | AD7687BCPZ-R2 | AD7942BCPZ-R2 | AD7680ACPZ-R2 |
|---|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 10-LFCSP-WD (3x3) | 10-LFCSP-WD (3x3) - same | 10-LFCSP-WD (3x3) - same | 10-LFCSP-WD (3x3) - same | 10-LFCSP-WD (3x3) - same | 10-LFCSP-WD (3x3) - same | 10-LFCSP-WD (3x3) - same |
| Resolution | 16 Bit | 16 Bit | 16 Bit | 16 Bit | 16 Bit | 14 Bit | 16 Bit |
| Sampling Rate | 250 kSPS | 250 kSPS | 250 kSPS | 500 kSPS (+100%) | 250 kSPS | 250 kSPS | 100 kSPS (-60%) |
| Input Type | Pseudo-differential unipolar | Pseudo-differential unipolar | Pseudo-differential unipolar | Pseudo-differential unipolar | True bipolar ±10 V / ±5 V | Pseudo-differential unipolar | Pseudo-differential unipolar |
| 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 | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 2.3 V to 5.5 V |
| Digital Interface | SPI / QSPI / MICROWIRE / DSP | SPI / QSPI / MICROWIRE / DSP | SPI / QSPI / MICROWIRE / DSP | SPI / QSPI / MICROWIRE / DSP | SPI / QSPI / MICROWIRE / DSP | SPI / QSPI / MICROWIRE / DSP | SPI / QSPI / MICROWIRE / DSP |
| Packaging Suffix | -R2 (250-unit reel) | -R2 reel | no suffix (tray) | -R2 reel | -R2 reel | -R2 reel | -R2 reel |
Key Differentiators
- Same package and pinout as 500 kSPS AD7686 - enables throughput upgrade without PCB redesign (vs AD7686BCPZ-R2)
- PulSAR family drop-in compatibility across speed and resolution grades (vs AD7942BCPZ-R2 (14-bit, 250 kSPS))
- Single 2.3 V-5.5 V supply eliminates need for bipolar power rails (vs AD7687BCPZ-R2 (±10 V bipolar input))
- Higher throughput than older AD7680 family (vs AD7680ACPZ-R2 (100 kSPS))
Design Notes
The exposed thermal pad (pin 4) of the 10-LFCSP-WD (3x3) package is the primary electrical ground and thermal path. It MUST be soldered to a PCB ground pour of at least 10 mm^2 with at least 5 thermal vias connecting to the inner ground plane. Without proper soldering, AC performance degrades by 2-4 dB SNR and the part may oscillate. Use a 4x4 via array of 0.2-mm finished holes for optimal thermal conductivity of approximately 50 C/W junction-to-ambient.
Place a 10 uF X7R ceramic decoupling capacitor within 5 mm of the VDD pin (pin 1) and a 100 nF X7R capacitor immediately adjacent to it for high-frequency noise suppression. The reference pin (pin 6) requires a 10 uF X7R ceramic capacitor with ESR less than 50 milliohms, placed within 5 mm of the pin. Avoid using tantalum capacitors on the reference pin as their higher ESR degrades 16-bit linearity and SNR performance, particularly above 100 kHz input bandwidth.
Estimated: For full 16-bit performance at 250 kSPS, keep analog input traces shorter than 25 mm and matched within 0.5 mm between IN+ and IN- to minimize common-mode-to-differential conversion. Route analog and digital ground returns separately and join them only at the ADC exposed pad. Avoid routing the SPI bus (SCK, SDO, SDI, CNV) parallel to analog input traces; cross at 90 degrees if crossing is unavoidable. Place a small ferrite bead (600 ohm at 100 MHz) on the VDD supply if switching noise from a DC-DC converter is present upstream.
At maximum throughput of 250 kSPS with 5 V supply, the AD7685CCPZ-R2 dissipates approximately 4 mW typical, so thermal management is rarely a concern. However, in enclosed environments above 70 C ambient or when sampling near 100% throughput continuously, ensure the exposed pad has at least 25 mm^2 of copper pour on the top layer and additional thermal vias to inner planes. The 50 C/W junction-to-ambient thermal resistance means junction temperature rise is negligible at typical operating conditions.
Common pitfalls when designing with the AD7685CCPZ-R2 include: (1) omitting the exposed-pad solder connection causing 6-10 LSB of INL error; (2) using too small a reference decoupling capacitor (must be at least 10 uF X7R); (3) failing to drive CNV low before each conversion per datasheet timing; (4) reading data without proper SCK framing per datasheet timing diagram; and (5) applying input voltages beyond absolute maximum ratings of VDD + 0.3 V or GND - 0.3 V. Always review the datasheet timing diagrams before writing SPI driver firmware.
Compliance Information
RoHS and REACH compliant per Analog Devices product page. Not AEC-Q100 qualified - consult Analog Devices automotive line for AEC-Q100 PulSAR equivalents. Lead-free and halogen-free per package materials declaration.
