AD7856ARZ-REEL7 - 14-Bit 285kSPS 8-CH SAR ADC | Analog Devices
N.º de pieza: AD7856ARZ-REEL7 ⚠ Última compra| Cant. | Precio unitario | Total |
|---|---|---|
| 1 | $18.5 | $18,50 |
| 10 | $16.4 | $164,00 |
| 100 | $14.2 | $1.420,00 |
| 500 | $11.95 | $5.975,00 |
| 1.000 | $10.1 | $10.100,00 |
AD7856ARZ-REEL7 Descripción general
What is an SAR ADC? A successive approximation register analog-to-digital converter (SAR ADC) is a sample-and-hold based converter that performs a binary search across an internal DAC to determine each code. SAR ADCs are prized for deterministic latency, mid-to-high resolution (typically 12 to 18 bits), and excellent AC/DC linearity. In the ADC taxonomy, this part sits at: ADC -> data converter -> signal chain IC -> analog mixed-signal IC -> semiconductor. The AD7856ARZ-REEL7 belongs to Analog Devices' AD7856 family of low-power, single-supply SAR ADCs.
The AD7856 integrates self-calibration and system-calibration routines that execute on power-up, ensuring offset and gain accuracy over time and temperature. The device supports pseudo-differential or single-ended analog inputs across 8 channels multiplexed by an on-chip input MUX. The digital interface is SPI-/QSPI-/MICROWIRE-/8051-compatible, making the ADC easy to drop into most microcontroller and DSP systems. The -REEL7 suffix does not change electrical specs - it only changes the carrier tape format (7-inch reel, 1000-piece reels typical).
Typical applications include industrial process control, multi-channel data acquisition systems, battery-powered instrumentation, motor control feedback loops, and portable medical devices. The wide analog input range (0 V to VREF) and the ability to operate from a single 5 V rail make it well suited to 5 V MCU systems. Note that the AD7856ARZ-REEL7 has been reported as no longer manufactured on some distributor pages - check ADI's product page for current lifecycle status before designing in new systems.
When designing with this device, ensure that the analog inputs are properly buffered with low-impedance drivers and that the reference input is decoupled with a 10 uF (or larger) capacitor close to the REF pin. The internal calibration should be allowed to complete before the first conversion is read. The CONVST pin falling edge initiates a conversion; software should respect the stated acquisition and conversion timing budgets.
Alternativas directas para AD7856ARZ-REEL7 — mismo encapsulado, compatible pin a pin. Se excluyen las piezas de otro encapsulado que requieren retrabajo de la PCB.
Herramienta de comparación rápida — seleccione piezas alternativas para compararlas lado a lado:
AD7856ARZ
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
AD7856AR-REEL
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
AD7856KR-REEL7
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
AD7856ARZ-REEL7 Valores máximos y características eléctricas
| Resolución | 14 bit |
| Number of Channels | 8 (single-ended or pseudo-differential) |
| Frecuencia de muestreo | 285 kSPS |
| Architecture | SAR (Successive Approximation Register) |
| Tensión de alimentación | 5 V single (4.75 V to 5.25 V) |
| Analog Input Range | 0 V to VREF |
| Data Interface | SPI, QSPI, MICROWIRE, 8051-compatible serial |
| Calibration | Self- and system-calibration on power-up |
| Encapsulado | 24-pin SOIC (0.295 in / 7.50 mm body width) |
| Packaging Form | Tape & Reel, 7-inch reel (REEL7 suffix) |
| Input Type | Single-ended / pseudo-differential (per channel) |
| Estado RoHS | Compliant (Z suffix indicates lead-free) |
| Tipo de montaje | Surface Mount |
| Number of ADC Inputs | 4 or 8 (multiplexed) |
| Conversion Type | SAR with input track-and-hold |
Configuración de pines de AD7856ARZ-REEL7
| Pin 1 | AGND — Analog ground |
| Pin 2 | AVDD — Analog +5 V supply |
| Pin 3 | REF — Reference input/output (decouple with 10 uF cap) |
| Pin 4 | AGND — Analog ground |
| Pin 5 | AIN1 — Analog input channel 1 |
| Pin 6 | AIN2 — Analog input channel 2 |
| Pin 7 | AIN3 — Analog input channel 3 |
| Pin 8 | AIN4 — Analog input channel 4 |
| Pin 9 | AGND — Analog ground |
| Pin 10 | AIN5 — Analog input channel 5 |
| Pin 11 | AIN6 — Analog input channel 6 |
| Pin 12 | AIN7 — Analog input channel 7 |
| Pin 13 | AIN8 — Analog input channel 8 |
| Pin 14 | AGND — Analog ground |
| Pin 15 | DVDD — Digital +5 V supply |
| Pin 16 | DGND — Digital ground |
| Pin 17 | CONVST — Conversion start (active low) |
| Pin 18 | CS — Chip select (active low) |
| Pin 19 | SCLK — Serial clock input |
| Pin 20 | DOUT — Serial data output (read port) |
| Pin 21 | DIN — Serial data input (write port) |
| Pin 22 | BUSY — Conversion busy output |
| Pin 23 | CAL — Calibration control |
| Pin 24 | PD — Power-down control |
Aplicaciones típicas
AD7856ARZ-REEL7 es adecuado para 6 aplicacións: Multi-Channel Data Acquisition Systems, Industrial Process Control and PLC Analog Inputs, Battery-Powered Portable Instrumentation, Motor Control Current Sensing, Medical Patient Monitoring Devices, Test and Measurement Equipment Front-Ends.
Multi-Channel Data Acquisition Systems
The AD7856ARZ-REEL7 is ideally suited for multi-channel data acquisition systems (DAQ) where 8 single-ended sensor inputs must be digitized at moderate speeds. Its 8-channel input multiplexer, 14-bit resolution (305 uV per LSB at VREF=5 V), and 285 kSPS throughput allow one AD7856 to replace multiple slower ADCs while keeping the bill of materials compact. The single 5 V supply and SPI-compatible digital interface drop directly into most 5 V MCU or DSP hosts, while the on-chip self- and system-calibration maintains offset and gain accuracy over the industrial temperature range without periodic field recalibration.
Recomendado
Industrial Process Control and PLC Analog Inputs
In industrial process control and PLC analog input modules, the AD7856ARZ-REEL7 delivers 14-bit precision across 4 or 8 analog inputs while running from a single 5 V rail. Its 285 kSPS throughput is more than adequate for 4-20 mA loop digitizing at typical 100 Hz per-channel update rates, leaving ample timing headroom for sequential scanning of all 8 channels within a single PLC cycle. The SAR architecture provides zero-latency conversion - critical for closed-loop control - and the SPI interface connects to most industrial microcontrollers. On-chip calibration compensates sensor offset/gain drift caused by temperature cycling.
Recomendado
Battery-Powered Portable Instrumentation
Battery-powered portable instruments such as handheld multimeters, field data loggers, and portable diagnostic tools benefit from the AD7856ARZ-REEL7's combination of low power consumption and on-demand power-down modes. When used with the device's programmable power-down feature, the ADC drops to a few milliwatts between conversions, dramatically extending battery life. The 14-bit resolution is sufficient for most environmental and biomedical sensor front-ends, while the SOIC-24 package is compatible with hand-solderable prototyping and high-volume SMD assembly. Reference designs typically pair the AD7856 with a low-power MCU such as an MSP430 or Cortex-M0.
Recomendado
Motor Control Current Sensing
Closed-loop motor control systems frequently need to digitize multiple phase currents and a DC bus voltage within a PWM period. The AD7856ARZ-REEL7 handles this with its 285 kSPS throughput and 8 input channels - sampling 3 phase currents plus DC bus at over 70 kSPS per channel is feasible. The SAR architecture's deterministic acquisition timing avoids the latency artifacts of delta-sigma ADCs, making the AD7856 a reliable choice for FOC motor control. Pseudo-differential inputs reject common-mode switching noise from the inverter bridge, and the SPI interface streams conversion results directly to the motor control DSP.
Recomendado
Medical Patient Monitoring Devices
Medical patient monitoring equipment - including multi-parameter bedside monitors, ambulatory ECG/event recorders, and infusion pump controllers - require simultaneous digitizing of several low-frequency analog signals with reliable noise performance. The AD7856ARZ-REEL7's 8 input channels support ECG, SpO2, temperature, respiration, and pressure sensing from a single ADC, while 14-bit resolution (305 uV per LSB) is adequate for diagnostic-grade ECG (>1 mV signals). The SAR architecture's lack of pipeline delay is critical for synchronizing multi-channel waveforms, and the device's SPI interface pairs naturally with low-power medical MCUs.
Recomendado
Test and Measurement Equipment Front-Ends
Test and measurement instruments such as bench-top multimeters, oscilloscope front-end digitizers, and laboratory data acquisition chassis benefit from the AD7856ARZ-REEL7's combination of channel count and throughput. With 8 inputs at 285 kSPS, a single AD7856 can scan multiple measurement points inside an ATE fixture or oscilloscope front panel. The 14-bit resolution supports general-purpose signal measurement beyond simple on/off detection, and the on-chip calibration routines reduce the cost of factory gain/offset trimming. The SOIC-24 package simplifies fixture rework and probe station characterization.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para AD7856ARZ-REEL7 — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | AD7856ARZ | AD7856AR-REEL | AD7856KR-REEL7 |
|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 24-pin SOIC (7.5 mm wide) | 24-pin SOIC - same | 24-pin SOIC - same | 24-pin SOIC - same |
| Resolution | 14 bit | 14 bit | 14 bit | 14 bit |
| Sampling Rate | 285 kSPS | 285 kSPS | 285 kSPS | 285 kSPS |
| Number of Channels | 8 (single-ended/pseudo-differential) | 8 | 8 | 8 |
| Supply Voltage | 5 V single | 5 V single | 5 V single | 5 V single |
| RoHS / Lead-Free | Yes (Z suffix) | Yes | No (non-Z suffix) | No (K suffix) |
| Packaging Form | Tape & Reel, 7-inch | Tube | Tape & Reel | Tape & Reel, 7-inch |
Diferenciadores clave
- True 8-channel single-ended input with on-chip MUX (frente a AD7478AAKSZ-REEL (single-channel 8/10/12-bit ADC))
- Built-in self- and system-calibration (frente a AD7828KPZ-REEL (8-channel ADC without on-chip calibration))
- 285 kSPS throughput at 14-bit resolution (frente a AD7708BRU-REEL (16-bit sigma-delta, ~10 Hz update rate))
Notas de diseño
The AD7856 operates from a single 5 V supply. Decouple AVDD and DVDD separately with 10 uF tantalum (or low-ESR ceramic) plus a 0.1 uF ceramic capacitor placed within 5 mm of each supply pin. According to the AD7856 datasheet, separate analog and digital grounds should be joined at a single point near the ADC's AGND pin to prevent digital switching noise from corrupting analog conversions. Estimated: at 285 kSPS continuous conversion the device draws ~12 mA (60 mW), but with power-down enabled between bursts it can drop to microampere levels.
Place the reference decoupling capacitor (10 uF minimum) as close as possible to the REF pin with a short, wide trace to the AGND plane. Route analog input traces symmetrically to maintain channel-to-channel matching - the AD7856 multiplexes 8 inputs through a single sample-and-hold amplifier, so trace impedance mismatches show up as channel-dependent gain errors. Use a guard trace or ground fill around the analog input traces to reject switching noise from the digital SPI signals.
Do not start a conversion before the self-calibration routine completes - the AD7856 datasheet specifies a maximum calibration time of approximately 50 ms after power-up; reading conversion data before calibration finishes returns uncalibrated codes. Do not drive analog inputs above AVDD or below AGND - the input ESD diodes will conduct and corrupt the conversion. Finally, the BUSY pin must be monitored in software to avoid reading stale conversion data; the SPI read should only occur after BUSY goes high (conversion complete).
Información de cumplimiento
RoHS compliance indicated by 'Z' suffix in part number. Non-automotive part - AEC-Q100 not applicable. REACH compliance assumed but not explicitly verified from provided data.
