AD7851KN - 14-Bit 333 kSPS Serial ADC | Analog Devices
Teilenummer: AD7851KN ⚠ Letzte Bestellmöglichkeit| Menge | Stückpreis | Gesamt |
|---|---|---|
| 1 | $23.5 | $23,50 |
| 10 | $21.15 | $211,50 |
| 100 | $19.05 | $1.905,00 |
| 500 | $17.4 | $8.700,00 |
| 1.000 | $15.44 | $15.440,00 |
AD7851KN Übersicht
A successive-approximation register (SAR) ADC is a sampling converter that performs a binary search on the input voltage using an internal DAC and comparator; SAR ADCs are valued for deterministic latency, low-latency single-shot conversion, and inherent ease of single-supply operation. Within the converter/ADC product family, the AD7851KN sits at the integration level that sits below integrated microcontrollers with ADC peripherals but above discrete op-amp+counter sample-and-hold designs, occupying the middle of the data-acquisition signal chain where predictable timing and serial interfacing outweigh the need for very-high channel counts.
Key features include a pseudo-differential analog input with two programmable input ranges (0 V to VREF and 0 V to 2 x VREF, with unipolar coding only), built-in self-calibration and system-calibration modes for accuracy over time and temperature, multiple power-down options for low-power applications, and a serial interface compatible with most microcontrollers and DSPs via the active-low CONVST and serial-data framing. The K-grade models are guaranteed to retain 1 LSB DNL at the 285 kSPS rate across the full -40 C to +125 C automotive-industrial range.
The device architecture uses a capacitive charge-redistribution DAC in the SAR loop, with auto-calibration of offset and gain on demand; this corrects drift introduced by the internal reference buffer and the comparator over temperature. Conversion is initiated by the falling edge of CONVST, and data is clocked out on a single DOUT line with synchronous SCLK, reducing isolated-system wiring to three lines. The pseudo-differential input rejects common-mode noise on the DC input and is well suited for ratiometric measurements using an external reference and a transducer bridge.
Typical applications include industrial process-control analog input modules, multi-channel data-acquisition front ends, motor-control current and voltage sensing loops, instrumentation transducer signal conditioning, and legacy upgrade paths in systems designed around the original AD7851. The serial interface and small footprint also support portable data loggers and battery-powered test equipment where board area and power budget are constrained.
When designing with this part, provide a low-impedance reference of 2.5 V or 5 V at the REF pin through a 10 uF decoupling capacitor, and maintain a quiet analog ground to avoid coupling digital SCLK edges into the conversion result. The self-calibration routine should be issued at power-on and after any large temperature change to retain the 1 LSB DNL guarantee; without calibration, gain error can drift by several LSBs across the -40 C to +125 C range.
This page synthesizes the ADI datasheet specifications, current distributor stock from Octopart and Infinity-Semiconductor, and a Same-Brand Same-Family drop-in alternative set useful for designers migrating from end-of-life AD7851 builds to other 14-bit SAR ADCs.
Drop-in-Alternativen für AD7851KN – gleiches Gehäuse, Pin-kompatibel. Bauteile mit anderem Gehäuse, die eine PCB-Überarbeitung erfordern, sind ausgeschlossen.
Schnellvergleichstool – Wählen Sie Alternativbauteile für den Direktvergleich:
AD7851KRZ
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
AD7851KRZ-REEL
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
AD7851ARZ
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
AD7851JN
✅ Drop-In ⚠️ Spezifikationen ungeprüft📋 Referenzalternative (nicht im Katalog)
AD7851JRZ
✅ Drop-In ⚠️ Spezifikationen ungeprüft📋 Referenzalternative (nicht im Katalog)
AD7851KN Grenzwerte & elektrische Eigenschaften
| Auflösung | 14 bits |
| Architecture | SAR (Successive Approximation) |
| Throughput Rate (K-Grade) | 285 kSPS |
| Maximum Throughput Rate | 333 kSPS |
| DNL (K-Grade Max) | 1 LSB |
| Versorgungsspannung | 5 V single supply |
| Input Type | Pseudo-differential |
| Input Range | 0 V to VREF or 0 V to 2 x VREF (unipolar) |
| Serial Interface | SPI/QSPI/MICROWIRE-compatible |
| Calibration | Self-calibration and system-calibration |
| Power-Down Modes | Multiple low-power options |
| Operating Temperature (K-Grade) | -40 C to +125 C |
| Gehäuse | PDIP-24 (N-24) |
| Montageart | Through-Hole (DIP) |
| Lifecycle | Last Time Buy (per Analog Devices product page, Rev B datasheet) |
| Datasheet Revision | Rev. B |
AD7851KN Pin-Konfiguration
| Pin 1 | VSS — Negative supply (0 V) |
| Pin 2 | AGND — Analog ground reference |
| Pin 3 | REF — External reference input |
| Pin 4 | IN+ — Positive analog input |
| Pin 5 | IN- — Negative analog input (pseudo-differential) |
| Pin 6 | CAP1 — Capacitor pin for internal reference buffer |
| Pin 7 | CAP2 — Capacitor pin for reference bypass |
| Pin 8 | VDD — +5 V positive supply |
| Pin 9 | DGND — Digital ground reference |
| Pin 10 | SCLK — Serial clock input |
| Pin 11 | DOUT — Serial data output |
| Pin 12 | DIN — Serial data input for calibration registers |
| Pin 13 | CONVST — Conversion start, active low |
| Pin 14 | CS — Chip select, active low |
| Pin 15 | BUSY — Conversion in progress, active low |
| Pin 16 | CAL — Initiate calibration, active low |
| Pin 17 | PD — Power-down mode select |
| Pin 18 | RANGE — Input range select (0=VREF, 1=2xVREF) |
| Pin 19 | NC — Not connected |
| Pin 20 | NC — Not connected |
| Pin 21 | NC — Not connected |
| Pin 22 | NC — Not connected |
| Pin 23 | NC — Not connected |
| Pin 24 | VSS — Negative supply (0 V) |
Typische Anwendungen
AD7851KN ist geeignet für 6 Anwendungs: Industrial Process Control Analog Input Modules, Multi-Channel Data Acquisition Front Ends, Motor Control Current and Voltage Sensing, Instrumentation Transducer Signal Conditioning, Battery-Powered Data Loggers and Portable Test Equipment, Legacy AD7851 System Upgrade Paths.
Industrial Process Control Analog Input Modules
The AD7851KN's 14-bit resolution, 285 kSPS K-grade throughput, and -40 C to +125 C operating range make it well suited to industrial process control analog-input modules. Its pseudo-differential input drives ratiometric measurements from 4-20 mA current loops or resistive bridges by tying IN- to a mid-rail reference. The SPI-compatible serial port minimizes opto-isolator channel count across the field/control isolation barrier, lowering BOM cost. Built-in self-calibration corrects offset and gain drift that accumulates from years of thermal cycling in field cabinets.
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Multi-Channel Data Acquisition Front Ends
Pseudo-differential inputs fed through an external MUX let the AD7851KN serve as the front-end digitizer in multi-channel data-acquisition systems for instrumentation. The 285 kSPS K-grade rate is well matched to multiplexed scanning of 8-16 channels at 10 kHz each, providing roughly 14 noise-free bits after averaging. The serial interface reduces routing congestion on dense mixed-signal boards where the analog front end and backplane share a confined area. Self-calibration corrects MUX-induced charge-injection artifacts on a per-channel basis.
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Motor Control Current and Voltage Sensing
The AD7851KN samples shunt-resistor current signals with 1 LSB DNL accuracy, which makes it a sensible choice for motor-control current and voltage sensing loops. Synchronous conversion on CONVST- lets the MCU trigger ADC reads at exactly the right phase of the PWM cycle, eliminating aliasing in field-oriented control loops. The serial interface avoids parallel ADC buses that would couple high-dv/dt switching noise into sensitive low-voltage DC sensing paths. Built-in system calibration nulls out I*R drop error in high-current shunt paths.
Empfohlen
Instrumentation Transducer Signal Conditioning
For instrumentation transducer signal conditioning, the AD7851KN's pseudo-differential input accepts load-cell, strain-gauge, and thermocouple-conditioned outputs directly. The device's calibration routines correct zero-point and gain drift that arises from aging strain gauges in field-deployed test equipment. Industrial -40 C to +125 C operation matches the typical spec of load-cell electronics used in weighing and force-measurement platforms. Serial data output simplifies galvanic isolation in medical and process-isolation instrument applications.
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Battery-Powered Data Loggers and Portable Test Equipment
Power-down modes built into the AD7851KN reduce current consumption between conversions, helping battery-powered data loggers achieve multi-month runtimes on standard AA cells. Wake-up latency from the lowest power-down state is acceptable for sub-1 kSPS sampling of slow-moving physical quantities like temperature and humidity. The 14-bit resolution combined with averaging in the MCU provides 16+ effective bits for slowly varying sensor signals. The serial interface allows the logger MCU to share a single SPI bus with an SD card for storage.
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Legacy AD7851 System Upgrade Paths
Engineers maintaining original AD7851 designs can move directly to the AD7851KN for the same footprint, last-time-buy silicon used in fielded equipment. Where PCB redesign is acceptable, the AD7851KRZ preserves pin functionality in a smaller SOIC-24 outline with lead-free compliance. For brand-new designs, an active migration path to AD7691BCPZRL keeps the same SAR architecture, same pseudo-differential inputs, and a 14-bit resolution curve, while reducing power and PCB area.
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Zusammenfassung der empfohlenen Produkte
Technische Referenzdaten für AD7851KN – Vergleich, Designhinweise und Compliance-Informationen.
Auswahlhilfe
Vergleich mit Alternativen
| Parameter | Dieses Produkt | AD7851KRZ | AD7851ARZ | AD7851JN |
|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | PDIP-24 (N-24) | SOIC-24 (R-24) - through-hole to SMT rework required | SOIC-24 (R-24) - through-hole to SMT rework required | PDIP-24 (N-24) - exact same footprint |
| Resolution | 14 bits | 14 bits | 14 bits | 14 bits |
| Throughput Rate | 285 kSPS (K-grade) | 285 kSPS (K-grade) | 333 kSPS (A-grade) | 285 kSPS (J-grade at 0-70C) |
| DNL (max) | 1 LSB | 1 LSB | 2 LSB | 1 LSB (J-grade) |
| Operating Temperature | -40 C to +125 C | -40 C to +125 C (K-grade) | -40 C to +125 C (A-grade) | 0 C to +70 C (J-grade) |
| Lifecycle | Last Time Buy | Last Time Buy | Last Time Buy | Last Time Buy |
| Supply Voltage | 5 V single supply | 5 V single supply | 5 V single supply | 5 V single supply |
| Serial Interface | SPI/QSPI/MICROWIRE-compatible | SPI/QSPI/MICROWIRE-compatible | SPI/QSPI/MICROWIRE-compatible | SPI/QSPI/MICROWIRE-compatible |
Wichtigste Unterscheidungsmerkmale
- Industrial -40 C to +125 C K-grade operating range with 1 LSB DNL (vs. AD7851ARZ (A-grade))
- Through-hole PDIP-24 footprint for legacy industrial designs (vs. AD7851KRZ (SOIC-24))
- Built-in self-calibration and system-calibration routines (vs. Generic external calibration via host MCU software)
Designhinweise
Estimated: at a 5 V supply and a 285 kSPS conversion rate, the AD7851KN draws typically 5 mA active (25 mW) per the Analog Devices Rev B datasheet. Power-down mode can lower quiescent current to tens of microamps between conversions in battery-powered applications. Place a 0.1 uF ceramic decoupling capacitor within 5 mm of the VDD pin and a 10 uF tantalum or ceramic bulk capacitor near the analog supply entry; bypassing is mandatory to maintain 14-bit noise performance during bursts of bus activity.
Keep analog inputs and the REF pin traces routed over a continuous analog ground plane; avoid routing SCLK and DOUT traces across the analog input traces because the high-frequency edges couple into the kSPS conversion and add noise to the LSBs. A ground-isolation moat around the REF pin capacitors is recommended to prevent REF current transients from corrupting conversion results. Estimated: 14-bit at 285 kSPS resolution requires about 1 cm maximum separation between the input traces and any digital clocking trace.
Failure to issue the calibration routine at power-on is one of the most common causes of field failures on AD7851 designs - both offset and gain error drift across the -40 C to +125 C industrial range if uncalibrated, potentially adding up to 10 LSB of error. The CONVST signal must return high before the next falling edge to avoid missing the start-of-conversion handshake; do not leave CONVST floating because the internal pull-up weakly biases the start logic. According to the ADI Rev B datasheet, the input range selection via the RANGE pin must be valid during calibration or the calibration registers store an offset error.
Compliance-Informationen
RoHS/REACH compliance information for the PDIP-24 lead-finish variant of AD7851KN was not present in the Verified Web Data; the SOIC-24 KRZ variant is typically lead-free in modern Analog Devices parts. Last Time Buy status per analog.com product page. AEC-Q100 is not applicable for this converter (industrial-grade only).
