AD977ABR - 16-Bit 200kSPS Serial SAR ADC | 20-SOIC | ADI
MPN: AD977ABR ✓ Hoạt độngAD977ABR Tóm tắt
An ADC (analog-to-digital converter) is a data-converter integrated circuit that samples a continuous analog input voltage and produces a corresponding digital code at its output. SAR ADCs use a binary-search successive-approximation register together with an internal DAC to resolve each conversion in N clock cycles for N-bit precision; they are valued for zero pipeline latency, deterministic behavior, low power, and excellent DC linearity. SAR converters occupy a unique position in the data-converter hierarchy between high-speed flash/pipeline ADCs (>10 MSPS) and slow integrating/sigma-delta ADCs (audio, precision DC). The AD977A family is one of the classic low-power industrial SAR ADCs of the 1990s and remains in production for installed-base applications.
Key features include an aperture delay of 5 ns, track-and-hold bandwidth of 2 MHz, and a power-down mode that reduces quiescent dissipation to 50 µW for battery-powered designs. The serial interface is compatible with standard SPI/QSPI/MICROWIRE hosts, simplifying connection to microcontrollers and DSPs. Input protection diodes are absent on the analog input pin, so external clamping is required when the input can exceed the supply rails.
Typical applications include industrial process control data acquisition, multichannel PLC analog input modules, portable instrumentation, weighing scales, and remote sensor digitizers. The combination of ±5 V true-bipolar input range and serial output makes the part especially well suited to legacy PLCs and 4-20 mA loop digitizers. Designers should observe the datasheet's reference decoupling and analog-input filtering guidelines to realize the rated INL/DNL and signal-to-noise ratio, and should add an external TVS/Schottky clamp at the analog input when transients beyond ±5 V are possible.
Bộ thay thế dễ dàng lắp đặt cho AD977ABR — cùng gói, chân-to-chân tương thích. Các bộ phận yêu cầu hàn PCB bị loại trừ.
Các biến thể trong loạt này
Các mẫu cùng loạt có thể lắp đặt dễ dàng tương thích với AD977ABR (cùng hình factor và footprint) — khác nhau ở Supply Voltage, Resolution, Architecture, Data Interface, Package.
AD977AR
✅ Drop-In ⚠️ Thông số chưa được xác minhLiên hệ để biết giá
Xem tài liệu →AD977ABRZ
✅ Drop-In ⚠️ Thông số chưa được xác minh📋 Tham chiếu thay thế (không có trong danh mục)
AD977ACRZ
✅ Drop-In ⚠️ Thông số chưa được xác minh📋 Tham chiếu thay thế (không có trong danh mục)
AD977ABR-REEL
✅ Drop-In ⚠️ Thông số chưa được xác minh📋 Tham chiếu thay thế (không có trong danh mục)
AD7674ACPZRL
✅ Drop-InLiên hệ để biết giá
Xem tài liệu →AD977ABR Tỷ lệ tối đa & tính chất điện
| Độ phân giải | 16 bit |
| Architecture | Successive Approximation (SAR) |
| Number of Channels | 1 |
| Throughput Rate | 200 kSPS |
| Điện áp cung cấp | +5 V single |
| Power Dissipation (max) | 100 mW |
| Power-Down Mode Current | 50 µW (typical) |
| Input Ranges (unipolar) | 0 V to 5 V; 0 V to 4 V |
| Input Ranges (bipolar) | ±5 V; ±3.3 V |
| Digital Interface | Serial (SPI/QSPI/MICROWIRE-compatible) |
| Aperture Delay | 5 ns |
| Track-and-Hold Bandwidth | 2 MHz |
| Hộp | 20-pin SOIC (R-20), wide-body |
| Khoảng nhiệt độ hoạt động | -40 °C to +85 °C (industrial) |
| Kiểu lắp đặt | Surface Mount |
| Lead-Free / RoHS | Compliant |
Cấu hình chân AD977ABR
| Chân 1 | VREF — Internal reference voltage output (decoupling cap) |
| Chân 2 | R1IN — Input range setting resistor 1 node |
| Chân 3 | R2IN — Input range setting resistor 2 node |
| Chân 4 | AIN — Analog input |
| Chân 5 | AGND — Analog ground (sense) |
| Chân 6 | AGND — Analog ground (force) |
| Chân 7 | CAL — Calibration enable / mode select |
| Chân 8 | PD — Power-down input (active high) |
| Chân 9 | RESET — Reset input |
| Chân 10 | AVDD — +5 V analog supply |
| Chân 11 | AVDD — +5 V analog supply |
| Chân 12 | SCLK — Serial clock input |
| Chân 13 | SDOUT — Serial data output |
| Chân 14 | DVDD — +5 V (or +3 V) digital supply |
| Chân 15 | DGND — Digital ground |
| Chân 16 | TAG — Tag input for data tagging |
| Chân 17 | CONVST — Conversion start input |
| Chân 18 | CS — Chip select (active low) |
| Chân 19 | BUSY — Conversion busy output (active high) |
| Chân 20 | DRDY — Data ready output |
Ứng dụng tiêu biểu
AD977ABR phù hợp cho 6 Áp dụngs: Industrial Process Control / PLC Analog Input Modules, Multichannel Data Acquisition Boards, Portable Battery-Powered Instrumentation, Weigh Scale and Force Measurement Systems, Remote Sensor and Telemetry Digitizers, Medical and Analytical Instrumentation Front Ends.
Industrial Process Control / PLC Analog Input Modules
The AD977ABR's 16-bit resolution and ±5 V true-bipolar input range make it a natural fit for industrial PLC analog input modules digitizing 4-20 mA loops and ±10 V transducer outputs. With a single +5 V supply, 100 mW dissipation, and serial SPI-compatible output, the part drops directly onto a 4-channel PLC backplane. Compared with a sigma-delta alternative, the SAR architecture provides zero pipeline latency and deterministic conversion time, which is critical for closed-loop control. Throughput of 200 kSPS supports oversampling to suppress 50/60 Hz mains pickup while preserving bandwidth for fast process variables.
Được đề xuất
Multichannel Data Acquisition Boards
The AD977ABR is ideal for low-cost multichannel data-acquisition boards where a serial ADC simplifies board routing and reduces microcontroller pin count. Up to eight AD977ABR devices can share a single SPI bus via individual CS lines, yielding 8 channels of 16-bit data at 200 kSPS aggregate. The 2 MHz track-and-hold bandwidth preserves signal integrity on multiplexed inputs above the per-channel Nyquist rate. Designers typically add an input multiplexer (e.g., ADG708) plus an instrumentation amp front end (AD620) to build a 16-channel 16-bit DAS on a single 5 V rail.
Được đề xuất
Portable Battery-Powered Instrumentation
The AD977ABR's hardware power-down mode drops dissipation to 50 µW, making it suitable for battery-powered handheld instruments such as digital multimeters, handheld oscilloscope probes, and field calibrators. A single +5 V rail simplifies power architecture - typically a boost converter from a 3.6 V Li-ion cell. The 200 kSPS throughput enables accurate True-RMS and harmonic-distortion measurements on AC waveforms, while the SOIC-20 wide-body package provides good thermal margin for extended 4-wire Kelvin measurements in the field.
Được đề xuất
Weigh Scale and Force Measurement Systems
Weigh scales and load-cell digitizers benefit from the AD977ABR's 16-bit no-missing-codes performance and ±3.3 V or ±5 V bipolar input range that directly accommodates load-cell bridge outputs. The SAR architecture's excellent DC linearity (low INL/DNL) preserves calibration accuracy across the full scale range, while the serial output simplifies isolated data transfer across the bridge excitation barrier. A typical implementation pairs the AD977ABR with an AD8421 instrumentation amp and a low-drift reference such as the ADR01.
Được đề xuất
Remote Sensor and Telemetry Digitizers
Remote sensor digitizers in SCADA, weather stations, and pipeline monitoring benefit from the AD977ABR's single +5 V supply, low power, and serial interface that minimizes cabling to a host microcontroller. The 50 µW power-down current lets the host duty-cycle the ADC for very low average power in solar-powered remote installations. With 200 kSPS capability the part oversamples to suppress noise while keeping duty cycle low. Analog Devices' ADuC847 family of microcontrollers is a popular host, providing integrated references and excitation for the loop.
Được đề xuất
Medical and Analytical Instrumentation Front Ends
Bench-top medical analyzers (chemistry, hematology, immunoassay) and environmental monitors use the AD977ABR to digitize photodiode, conductivity, and ion-selective-electrode signals with 16-bit precision. The part's low integral nonlinearity preserves calibration curves over the full-scale range, while the serial output connects directly to the analyzer's embedded controller. Pairing the AD977ABR with the AD8628 chopper-stabilized op-amp achieves sub-LSB noise levels suitable for clinical-grade measurements.
Được đề xuất
Tóm tắt các sản phẩm được đề xuất
Dữ liệu tham khảo kỹ thuật cho AD977ABR — so sánh, hướng dẫn thiết kế và thông tin tuân thủ.
Hướng dẫn chọn lựa
So sánh với các sản phẩm thay thế
| Tham số | Sản phẩm này | AD977AR | AD977ABRZ | AD977ACRZ | AD7674ACPZRL |
|---|---|---|---|---|---|
| Package | SOIC-20 (R-20) | SOIC-20 (R-20) - same | SOIC-20 (R-20) - same | SOIC-20 (R-20) - same | LFCSP-48 - different |
| Brand | Analog Devices | Analog Devices - same | Analog Devices - same | Analog Devices - same | Analog Devices - same |
| Resolution | 16 bit | 16 bit | 16 bit | 16 bit | 16 bit |
| Throughput | 200 kSPS | 100 kSPS (-50%) | 200 kSPS (same) | 200 kSPS (same) | 800 kSPS (+300%) |
| Architecture | SAR (single-channel) | SAR (single-channel) | SAR (single-channel) | SAR (single-channel) | SAR (single-channel) |
| Supply Voltage | +5 V single | +5 V single | +5 V single | +5 V single | +5 V single |
| Power Dissipation | 100 mW max | 100 mW max | 100 mW max | 100 mW max | 110 mW max (+10%) |
| Input Range (max bipolar) | ±5 V true bipolar | ±5 V true bipolar | ±5 V true bipolar | ±5 V true bipolar | ±5 V true bipolar |
| Digital Interface | Serial (SPI/QSPI/MICROWIRE) | Serial (SPI/QSPI/MICROWIRE) | Serial (SPI/QSPI/MICROWIRE) | Serial (SPI/QSPI/MICROWIRE) | Parallel / Serial selectable |
| Lead-Free / RoHS | Compliant | Non-compliant (matte-tin) | Compliant | Compliant | Compliant |
Bảo phân biệt quan trọng
- 200 kSPS in true ±5 V bipolar input - rare for legacy SAR ADC family (vsAD977AR)
- Modern lead-free / RoHS-compliant packaging option in same SOIC-20 (vsAD977ABR (matte-tin))
- Zero pipeline latency SAR architecture for closed-loop control (vsAD7674ACPZRL)
Ghi chú thiết kế
Estimated: at +5 V supply and 200 kSPS continuous conversion, average supply current is approximately 20 mA per datasheet, yielding about 100 mW dissipation. Add a 10 µF tantalum + 0.1 µF ceramic decoupling pair close to each AVDD/DVDD pin pair. Tie the analog and digital ground planes together at one point under the IC body to avoid ground-loop noise coupling through the reference. Use the hardware PD (pin 8) to drop standby dissipation to 50 µW in battery-powered designs.
The analog input pin has NO internal ESD protection diodes to the supply rails. Apply an external BAT54S Schottky clamp or TVS to AGND and AVDD when the input can exceed ±5 V (e.g. from transients on a long sensor cable). Without this clamp, an input transient above AVDD or below AGND will forward-bias the ESD structure and may permanently damage the ADC. This is the single most common field issue documented in the AD977A errata.
Place the input range-setting resistors (R1, R2 between pins 2, 3 and AVDD/AGND) within 5 mm of the package, and add a 1 nF ceramic across AIN to AGND right at the pin. The 2 MHz track-and-hold bandwidth requires a low-impedance input driver - a series resistor between the op-amp output and AIN greater than 1 kΩ will cause conversion errors due to ADC input kick-back. Use an op-amp such as AD8628 or AD797 with adequate current drive to settle the ADC input within the acquisition window.
Route the serial interface lines (SCLK, SDOUT, CONVST, CS) away from the analog input trace and the reference decoupling node. Keep the analog input trace length below 25 mm and surround it with a ground pour tied to AGND only. Place the 22 µF VREF bypass cap as close as possible to pin 1. According to the AD977A datasheet layout recommendations, the AGND plane should extend under the entire ADC body to provide a low-impedance return path for the reference and analog input currents.
Thông tin tuân thủ
Per the Vyrian product listing (2026-10-12), AD977ABR ships with lead-free/RoHS-compliant terminal finish. AEC-Q100 automotive grade is not qualified; for automotive designs consider the AD7862ARS or AD7899AR-3REEL family members which offer extended temperature variants.
