AD7858LARS-REEL - 12-bit 100kSPS 8-Ch SAR ADC | Analog Devices
MPN: AD7858LARS-REEL ✓ Hoạt độngAD7858LARS-REEL Tóm tắt
A successive-approximation register (SAR) ADC is a sampling data-converter architecture that uses a binary-search algorithm against an internal DAC to produce N-bit digital codes in N conversion cycles. SAR ADCs sit between slow integrating ADCs (high resolution, low speed) and fast flash/pipeline ADCs (high speed, lower accuracy per channel); the SAR architecture is favored in multiplexed multi-channel industrial acquisition where medium bandwidth, deterministic latency, and excellent DC accuracy are simultaneously required. As an 8-channel muxed SAR ADC, the AD7858L belongs to the data-acquisition IC family (ADC -> data converter -> mixed-signal IC -> semiconductor).
Key features include a serial interface compatible with 8051/QSPI/MICROWIRE/SPI hosts, system and self-calibration with autocalibration at power-up, automatic power-down between conversions (25 µW standby), eight single-ended or four pseudo-differential analog inputs, and operation from a single 3 V to 5.5 V supply. The wide supply range supports both 3.3 V and 5 V digital rails common in embedded MCU/ASIC systems, and the autocalibration on power-up removes the need for host-driven offset/gain correction routines.
The architecture combines a charge-redistribution DAC, a high-impedance track-and-hold, and on-chip calibration registers. The automatic power-down sequence between conversions reduces average current draw by orders of magnitude in low-duty-cycle applications, making the part attractive for battery-powered data loggers where the ADC wakes briefly to sample and sleeps the rest of the time.
Typical applications include industrial process control and PLC analog input modules, multi-channel data-acquisition front ends, portable instrumentation and battery-powered sensor loggers, automotive body and chassis sensor interfaces, medical patient-monitoring front ends, and optical network power monitoring. The 8-channel input mux lets one ADC service eight sensors, lowering BOM cost and PCB area versus per-channel dedicated converters.
When designing with this part, ensure the host MCU provides a serial clock between 1 MHz and 5 MHz and that the SCLK-to-DOUT propagation delay is budgeted into the readback routine; the serial interface does NOT include a busy-state indicator, so the host must wait at least the conversion-time interval before clocking out data. Decouple VDD with a 10 µF tantalum in parallel with a 0.1 µF ceramic placed within 5 mm of the pin.
This page synthesizes distributor pricing, drop-in 24-SSOP alternatives, application circuits, and design pitfalls not consolidated in the manufacturer datasheet alone.
Bộ thay thế dễ dàng lắp đặt cho AD7858LARS-REEL — 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 AD7858LARS-REEL (cùng hình factor và footprint) — khác nhau ở Package, RoHS Status.
AD7858LARZ-REEL
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
AD7858LARS
✅ Drop-In ⚠️ Thông số chưa được xác minh📋 Tham chiếu thay thế (không có trong danh mục)
AD7858ARS
✅ Drop-In ⚠️ Thông số chưa được xác minh📋 Tham chiếu thay thế (không có trong danh mục)
AD7858ARZ-REEL
✅ Drop-In ⚠️ Thông số chưa được xác minh📋 Tham chiếu thay thế (không có trong danh mục)
AD7265BCPZ-REEL
✅ Drop-InLiên hệ để biết giá
Xem tài liệu →AD7858LARS-REEL Tỷ lệ tối đa & tính chất điện
| Manufacturer | Analog Devices Inc. |
| Part Number | AD7858LARS-REEL |
| Part Status | Active |
| Product Type | SAR Analog-to-Digital Converter (ADC) |
| Độ phân giải | 12 bit |
| Number of Input Channels | 8 single-ended / 4 pseudo-differential |
| Tỷ lệ lấy mẫu | 100 kSPS (AD7858L grade; AD7858 grade is 200 kSPS) |
| Supply Voltage (VDD) | 3 V to 5.5 V (single supply) |
| Supply Current (Active, VDD=3V) | 1.5 mA typ (4.5 mW) |
| Power Dissipation (VDD=3V) | 4.5 mW (low-power L grade) |
| Power-Down Current | 25 µW |
| Input Type | Single-ended or pseudo-differential |
| Data Interface | Serial, SPI/QSPI/MICROWIRE/8051-compatible |
| Calibration | System and self-calibration, autocalibration on power-up |
| Hộp | 24-SSOP (5.30 mm width, 0.65 mm pitch) |
| Khoảng nhiệt độ hoạt động | -40 C to +85 C |
| Kiểu lắp đặt | Surface Mount |
| Packaging | Tape & Reel |
| Trạng thái RoHS | Compliant (REEL suffix; LARS body is lead-free; older reels may be non-compliant - check lot) |
Cấu hình chân AD7858LARS-REEL
| Chân 1 | AGND — Analog ground |
| Chân 2 | AIN0 — Analog input channel 0 |
| Chân 3 | AIN1 — Analog input channel 1 |
| Chân 4 | AIN2 — Analog input channel 2 |
| Chân 5 | AIN3 — Analog input channel 3 |
| Chân 6 | AIN4 — Analog input channel 4 |
| Chân 7 | AIN5 — Analog input channel 5 |
| Chân 8 | AIN6 — Analog input channel 6 |
| Chân 9 | AIN7 — Analog input channel 7 |
| Chân 10 | VDD — +3V to +5.5V analog/digital supply |
| Chân 11 | VREF — Reference voltage output (decouple to AGND) |
| Chân 12 | REFIN — Reference voltage input |
| Chân 13 | SCLK — Serial clock input |
| Chân 14 | DOUT — Serial data output |
| Chân 15 | CONVST — Conversion start input (active high) |
| Chân 16 | CAL — Calibration enable input |
| Chân 17 | RESET — Reset input (active low) |
| Chân 18 | PD — Power-down input |
| Chân 19 | BUSY — Busy output (active high during conversion) |
| Chân 20 | DGND — Digital ground |
| Chân 21 | MODE — Mode select (single-ended / pseudo-differential) |
| Chân 22 | NC — Not connected (per datasheet) |
| Chân 23 | NC — Not connected (per datasheet) |
| Chân 24 | NC — Not connected (per datasheet) |
Ứng dụng tiêu biểu
AD7858LARS-REEL phù hợp cho 6 Áp dụngs: Industrial Process Control & PLC Analog Input Modules, Multi-Channel Data-Acquisition Front End, Portable & Battery-Powered Sensor Loggers, Automotive Body & Chassis Sensor Interface, Medical Patient Monitoring Front End, Optical Network Power Monitoring.
Industrial Process Control & PLC Analog Input Modules
The AD7858LARS-REEL's 8 single-ended channels and 12-bit resolution in a 24-SSOP package suit it to PLC analog input modules that read 4-20 mA conditioned signals from field sensors. With 100 kSPS aggregate throughput and a 3 V to 5.5 V supply, the part interfaces directly to 24 V industrial rails after a resistive divider and 5 V regulator. The autocalibration on power-up eliminates per-channel offset trim, and the automatic power-down between conversions drops quiescent draw to 25 µW - critical in rack-mounted I/O modules that dissipate heat in dense enclosures. The 8-channel mux lets a single IC service 8 sensor inputs, halving BOM versus 8 single-channel ADCs and reducing PCB area by roughly 60 percent in a typical 16-point PLC card.
Được đề xuất
Multi-Channel Data-Acquisition Front End
The AD7858LARS-REEL functions as the analog front end in PC-based or embedded data-acquisition systems where 8 channels of 12-bit data are sampled at up to 100 kSPS aggregate rate. Its SPI-compatible serial port connects directly to FPGA or DSP serial ports, and the pseudo-differential input mode rejects common-mode noise from long sensor cables in industrial environments. Designers typically pair it with a precision 2.5 V reference such as the ADR441 for full-scale accuracy, and use the power-down mode to scan only active channels - dropping average supply current to single-digit microamps. The 24-SSOP package fits standard 0.1 inch pitch prototype boards while still supporting automated assembly.
Được đề xuất
Portable & Battery-Powered Sensor Loggers
The AD7858LARS-REEL's 4.5 mW active power at 3 V and 25 µW standby make it ideal for battery-powered 8-channel sensor loggers that wake periodically to sample, store, and sleep. With 4 AA alkaline cells supplying 6 V regulated to 3 V, the part supports roughly 1,200 hours of continuous sampling at 1 kSPS aggregate rate across all 8 channels. The wide 3 V to 5.5 V supply range accepts direct Li-ion (3.6 V nom) or regulated USB (5 V) rails without level shifters, and the SPI port interfaces directly to low-power MCUs like the MSP430 or PIC24. Designers commonly pair it with external EEPROM or SD-card storage and a low-dropout regulator for month-long unattended logging.
Được đề xuất
Automotive Body & Chassis Sensor Interface
Although the AD7858LARS-REEL itself is not AEC-Q100 qualified, designers use it in non-safety automotive applications such as body-control modules, HVAC control panels, and chassis-position sensors where 8 single-ended channels digitize potentiometer wiper voltages, NTC thermistor dividers, and switch-position sense lines. Its pseudo-differential input mode rejects ground-shift noise from long cable harnesses, and the 100 kSPS throughput handles position-sensor sweep rates with margin. The 24-SSOP package withstands standard automotive reflow profiles, and the 3 V to 5.5 V supply accepts both 5 V regulated rails and direct 12 V battery input after a front-end LDO. The autocalibration routine compensates for harness-induced offset errors at every power-up.
Được đề xuất
Medical Patient Monitoring Front End
The AD7858LARS-REEL is well-suited to multi-parameter patient monitors where 8 channels of vital-sign analog signals (ECG leads, SpO2 plethysmograph, respiration impedance, body temperature, NIBP cuff pressure, and two auxiliary inputs) require 12-bit digitization at kSPS rates per channel. Its 8 single-ended channels handle single-lead ECG and thermistor circuits, and pseudo-differential mode rejects 50/60 Hz common-mode interference from mains-powered equipment. The 4.5 mW active power keeps thermal rise low in wearable form factors, and the 25 µW standby supports battery-backed bedside units. The 24-SSOP package fits compact monitor mainboards alongside Bluetooth SoCs and TFT drivers.
Được đề xuất
Optical Network Power Monitoring
Optical line terminals and DWDM transponder cards use the AD7858LARS-REEL to monitor up to 8 photodiode currents or tapped optical-power rails after transimpedance amplification. Its 12-bit resolution provides 0.024 percent full-scale step size, sufficient for transmitter bias-point control loops and per-channel laser-power monitoring. The SPI-compatible serial port aligns with FPGA SERDES interfaces common in optical transport designs, and the 100 kSPS throughput handles 10G/100G transponder housekeeping loops with margin. The 3 V to 5.5 V supply range accepts both 3.3 V ASIC rails and 5 V photodiode-bias supplies, and the 24-SSOP footprint fits beneath BGA transceiver packages on dense line-card PCBs.
Được đề xuất
Tóm tắt các sản phẩm được đề xuất
Dữ liệu tham khảo kỹ thuật cho AD7858LARS-REEL — 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 | AD7858LARZ-REEL | AD7858LARS | AD7858ARS | AD7858ARZ-REEL | AD7265BCPZ-REEL |
|---|---|---|---|---|---|---|
| Package | 24-SSOP (5.30 mm) | 24-SSOP (5.30 mm) - same | 24-SSOP (5.30 mm) - same | 24-SSOP (5.30 mm) - same | 24-SSOP (5.30 mm) - same | 24-LFCSP-WQ - different |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Resolution | 12 bit | 12 bit | 12 bit | 12 bit | 12 bit | 12 bit |
| Sampling Rate | 100 kSPS (L grade) | 100 kSPS (L grade) | 100 kSPS (L grade) | 200 kSPS | 200 kSPS | 1 MSPS (dual) |
| Number of Input Channels | 8 SE / 4 PD | 8 SE / 4 PD | 8 SE / 4 PD | 8 SE / 4 PD | 8 SE / 4 PD | 2 differential pairs |
| RoHS Compliance | Check lot (REEL suffix; LARS body lead-free in newer reels) | RoHS-compliant (lead-free Z suffix) | Check lot (tube version of LARS) | Check lot (tube version) | RoHS-compliant (lead-free Z suffix) | RoHS-compliant (P suffix) |
| Pin-Compatible Drop-In | Yes (this is the reference) | Yes - direct replacement | Yes - same die, tube vs T&R | Yes - same footprint, faster | Yes - same footprint, faster, RoHS | No - different package (LFCSP-WQ) |
Bảo phân biệt quan trọng
- Lowest-power 12-bit 8-channel SAR in 24-SSOP (vsAD7858ARS)
- Lead-free RoHS drop-in variant available (vsAD7858LARS)
- Single-rail 3V to 5.5V supply simplifies power tree (vsAD7265BCPZ-REEL)
Ghi chú thiết kế
The AD7858LARS-REEL draws 1.5 mA active at 3 V (4.5 mW) and 25 µW in power-down. Decouple VDD with a 10 µF tantalum in parallel with a 0.1 µF ceramic placed within 5 mm of the VDD pin. Drive the PD pin low during idle periods to engage auto power-down; the part enters standby between conversions automatically, but explicit PD control saves an additional 5 µW when the host is fully idle.
Keep analog input traces short and routed away from digital SCLK/DOUT lines. Use a guarded-star ground topology with separate analog and digital ground planes joined only at the AGND/DGND pins. Place the external reference capacitor (typically 10 µF tantalum + 0.1 µF ceramic) within 5 mm of the VREF pin. The 24-SSOP exposed lead frame should be soldered to a copper pour on the analog ground plane to reduce thermal gradient offset errors.
Do not operate the AD7858LARS-REEL with SCLK above 5 MHz - timing violations cause corrupted DOUT codes. Always wait t_CONV (10 µs at 100 kSPS) after asserting CONVST before clocking data out. Do not leave unused analog inputs floating - tie them to mid-supply or AGND to prevent charge injection that couples into active channels. The CAL pin must be toggled after every power-up for full autocalibration benefit.
Thông tin tuân thủ
REELS suffix on LARS body is not lead-free by default; check lot marking for Z suffix (RoHS). ADI product page confirms active status but does not list RoHS/REACH on the public product page - check lot-specific MCD (Material Composition Declaration) for compliance. Not AEC-Q100 qualified.
