AD7878LN - 12-Bit 100kHz ADC with DSP Interface | Analog Devices
Référence : AD7878LN ✗ Fin de vie| Qté | Prix unitaire | Total |
|---|---|---|
| 1 | $35.5 | $35,50 |
| 10 | $32.2 | $322,00 |
| 100 | $28.9 | $2 890,00 |
| 500 | $25.4 | $12 700,00 |
| 1 000 | $22.1 | $22 100,00 |
AD7878LN Présentation
A successive-approximation register (SAR) ADC is a deterministic, sample-by-sample converter that compares the held input against an internal binary-weighted DAC using a precision comparator. SAR ADCs deliver deterministic latency, no pipeline delay, excellent DC linearity, and inherently strong anti-alias behavior when paired with an external analog filter, which is why they remain the preferred topology for multiplexed data-acquisition systems and DSP front ends where each conversion result must arrive on a known clock edge.
Key features of the AD7878LN include 12-bit resolution with no missing codes, a maximum 100 kHz throughput, integrated track/hold with 2 microsecond acquisition, on-chip 3 V reference, an 8-word deep FIFO that decouples conversion timing from DSP read timing, and a DSP-friendly parallel interface. The wide digital host compatibility spans the ADSP-2100, TMS320, and DSP56000 families, allowing the part to drop into a range of signal-processing designs without glue logic.
The device operates from a single +5 V analog supply plus a separate +5 V digital supply, providing isolation between the analog input chain and the noisy DSP bus. The architecture minimizes digital feedthrough into the analog front end and supports unipolar 0 to +5 V input ranges, simplifying signal conditioning for transducer and process-control signals.
Typical applications include DSP-based data acquisition front ends, process control and industrial instrumentation, motor control feedback sampling, multiplexed analog input subsystems, and portable or bench-top test equipment that requires deterministic 100 kHz sampling with a fast DSP read path. The integrated FIFO is particularly valuable when the DSP must service interrupts or run real-time algorithms without losing samples.
When designing with the AD7878LN, allocate board area for a 1 microfarad decoupling cap on each analog supply pin and place the analog input trace away from the parallel digital bus to limit coupling. Because the part is a through-hole 28-pin PDIP, it is best suited for prototype, instrumentation, and legacy industrial designs rather than high-density SMT assemblies; for SMT equivalents in the same family see the alternatives section.
Alternatives de remplacement direct pour AD7878LN — même boîtier, compatible broche à broche. Les références à boîtier différent nécessitant une retouche du PCB sont exclues.
Outil de comparaison rapide — sélectionnez des références alternatives pour une comparaison côte à côte :
AD7878JNZ
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
AD7878LNZ
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
AD7878KNZ
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
AD7878BQ
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
AD7878JPZ
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
AD7878LN Valeurs maximales et caractéristiques électriques
| Résolution | 12 bit |
| Fréquence d'échantillonnage | 100 kHz |
| Architecture | SAR |
| Number of Input Channels | 1 |
| Input Type | Single-Ended |
| Plage de tension d'entrée | 0 V to +5 V (unipolar, with +5 V supply) |
| Track/Hold Acquisition Time | 2 microsecond |
| Conversion Time | 7 microsecond |
| Internal Reference | 3 V Zener reference (on-chip) |
| SNR at 10 kHz Input | 72 dB |
| Data Interface | Parallel DSP interface |
| On-Chip FIFO | 8-word deep |
| Analog Supply Voltage | +5 V |
| Digital Supply Voltage | +5 V |
| Plage de température de fonctionnement | 0 C to +70 C (commercial) |
| Boîtier | 28-pin PDIP (N-28) through-hole |
| Type de montage | Through-Hole |
| Technology | LC2MOS |
Configuration des broches de AD7878LN
| Broche 1 | VIN — Analog input |
| Broche 2 | AGND — Analog ground |
| Broche 3 | REF — 3 V internal Zener reference output / reference decoupling |
| Broche 4 | CAP — Reference bypass capacitor |
| Broche 5 | VSS — Negative supply (ground) |
| Broche 6 | CS — Chip select (active low) |
| Broche 7 | RD — Read strobe (active low) |
| Broche 8 | WR — Write / conversion start (active low) |
| Broche 9 | BUSY — Conversion in progress (active high) |
| Broche 10 | FS — Frame sync for DSP interface |
| Broche 11 | SCLK — Serial clock for DSP interface |
| Broche 12 | DGND — Digital ground |
| Broche 13 | D0 — Data bit 0 (LSB) |
| Broche 14 | D1 — Data bit 1 |
| Broche 15 | D2 — Data bit 2 |
| Broche 16 | D3 — Data bit 3 |
| Broche 17 | D4 — Data bit 4 |
| Broche 18 | D5 — Data bit 5 |
| Broche 19 | D6 — Data bit 6 |
| Broche 20 | D7 — Data bit 7 |
| Broche 21 | D8 — Data bit 8 |
| Broche 22 | D9 — Data bit 9 |
| Broche 23 | D10 — Data bit 10 |
| Broche 24 | D11 — Data bit 11 (MSB) |
| Broche 25 | NC — Not connected (per datasheet) |
| Broche 26 | NC — Not connected (per datasheet) |
| Broche 27 | VDD — +5 V analog supply |
| Broche 28 | VLOGIC — +5 V digital supply |
Applications typiques
AD7878LN convient pour 6 applications: DSP-Based Data Acquisition Front End, Process Control and Industrial Instrumentation, Motor Control Feedback Sampling, Multiplexed Analog Input Subsystems, Portable Test and Measurement Equipment, Audio Bandwidth Signal Digitisation.
DSP-Based Data Acquisition Front End
The AD7878LN fits DSP-based data-acquisition front ends because it combines a 12-bit, 100 kHz SAR core with an integrated 8-word FIFO and a parallel DSP interface. The 2 microsecond track-and-hold and 7 microsecond conversion time give deterministic, sample-by-sample latency so ADSP-2100, TMS320, and DSP56000 processors receive each result on a known clock edge. The 72 dB SNR at 10 kHz input preserves audio-bandwidth dynamic range for instrumentation-grade digitisation. The FIFO decouples conversion timing from DSP read cycles, so the host can service interrupts or run real-time DSP algorithms without losing samples. Designers typically route the analog input through an external op-amp buffer and anti-alias filter, then drive the AD7878LN from a stable +5 V analog rail with 1 microfarad decoupling. This topology remains a workhorse for high-accuracy DSP front ends in laboratory and process-control equipment.
Recommandé
Process Control and Industrial Instrumentation
Industrial process-control boards benefit from the AD7878LN's deterministic SAR architecture, 0 to +5 V unipolar input range, and integrated 3 V Zener reference. The 100 kHz throughput is well matched to multiplexed thermocouple, strain-gauge, and 4-20 mA loop signals that have been conditioned by front-end instrumentation amplifiers. The 8-word FIFO buffers samples when the controller services network interrupts, which is critical for deterministic control loops. The commercial 0 to +70 C operating range fits panel-mount controllers, factory-floor test stations, and laboratory data loggers. The 28-pin PDIP package simplifies prototype rework and field replacement, while the parallel interface integrates cleanly with legacy PLC and industrial-PDA hosts. For designs requiring true industrial-temperature operation, designers should select the K or A grade variant.
Recommandé
Motor Control Feedback Sampling
The AD7878LN suits motor control current and position feedback sampling thanks to its 100 kHz conversion rate, deterministic SAR latency, and DSP-friendly parallel interface. The on-chip track-and-hold acquires the input in 2 microseconds, allowing shunt-resistor current-sense signals to be digitized before the next PWM edge. The integrated FIFO lets the DSP service encoder and commutation interrupts without losing conversion results, which is essential for high-speed field-oriented control loops. The +5 V analog and digital supply split keeps noisy gate-drive return currents out of the sensitive analog front end. Designers typically use one AD7878LN per phase-current channel, then drive the DSP from the parallel data bus. For three-phase systems, two AD7878LN channels plus a dedicated DC-bus channel provide complete feedback coverage.
Recommandé
Multiplexed Analog Input Subsystems
Multiplexed analog input subsystems benefit from the AD7878LN's single-channel 12-bit SAR with fast acquisition, on-chip reference, and DSP-side FIFO. An external analog multiplexer can scan multiple sensor inputs while the FIFO accumulates results, allowing the DSP to read the data in burst mode. The deterministic 7 microsecond conversion time gives the host a fixed per-channel budget, simplifying the multiplexer-timing schedule. The 72 dB SNR at 10 kHz preserves signal integrity for transducer and audio-bandwidth instrumentation channels. The 0 to +5 V unipolar input matches standard industrial signal levels after op-amp scaling. Designers typically pair the AD7878LN with an 8 or 16-channel CMOS multiplexer and a low-pass anti-alias filter for robust multi-channel digitisation.
Recommandé
Portable Test and Measurement Equipment
Portable and bench-top test equipment benefits from the AD7878LN's deterministic SAR latency, integrated 3 V reference, and parallel DSP interface. A 12-bit, 100 kHz digitiser is well matched to audio-bandwidth oscilloscope, signal-analyser, and data-logger front ends that capture transient or slowly-varying signals. The integrated FIFO lets a DSP or microcontroller service user-interface, display, and USB tasks without dropping samples. The single +5 V supply requirement simplifies portable battery-powered designs with a boost converter. The commercial 0 to +70 C operating range fits indoor and bench environments, while the through-hole PDIP package simplifies prototype rework and lab assembly. Designers typically add an input protection network, an instrumentation amplifier, and an anti-alias filter ahead of the ADC input pin.
Recommandé
Audio Bandwidth Signal Digitisation
Audio-bandwidth signal-digitisation applications benefit from the AD7878LN's 72 dB SNR at 10 kHz and 100 kHz maximum sampling rate. The deterministic SAR latency preserves waveform phase integrity, which is critical for audio analyser, spectrum analyser, and acoustic-measurement front ends. The integrated 3 V Zener reference and track-and-hold provide a complete signal chain in a single IC, reducing external component count and BOM cost. The parallel DSP interface streams samples directly into a DSP for FFT, filtering, or noise analysis. The 8-word FIFO absorbs DSP read latency during heavy signal-processing cycles, ensuring lossless capture. Designers typically add a 20 kHz anti-alias low-pass filter and an AC-coupled input amplifier ahead of the ADC for clean audio capture.
Recommandé
Récapitulatif des produits recommandés
Données de référence d'ingénierie pour AD7878LN — comparaison, recommandations de conception et informations de conformité.
Guide de sélection
Comparaison avec les alternatives
| Paramètre | Ce produit | AD7878JNZ | AD7878LNZ | AD7878KNZ | AD7878BQ | AD7878JPZ |
|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 28-pin PDIP (N-28) | 28-pin PDIP (N-28) - same | 28-pin PDIP (N-28) - same | 28-pin PDIP (N-28) - same | 28-pin CDIP (Q-28) - same pin count | 28-pin PLCC (P-28A) - same pin count |
| Resolution | 12 bit | 12 bit | 12 bit | 12 bit | 12 bit | 12 bit |
| Sampling Rate | 100 kHz | 100 kHz | 100 kHz | 100 kHz | 100 kHz | 100 kHz |
| Architecture | SAR | SAR | SAR | SAR | SAR | SAR |
| On-Chip FIFO | 8-word | 8-word | 8-word | 8-word | 8-word | 8-word |
| On-Chip Reference | 3 V Zener | 3 V Zener | 3 V Zener | 3 V Zener | 3 V Zener | 3 V Zener |
| Temperature Grade | Commercial (0 to +70 C) | Commercial (0 to +70 C) | Commercial (0 to +70 C) | Commercial (0 to +70 C) | Military | Commercial (0 to +70 C) |
| Mounting Type | Through-Hole | Through-Hole | Through-Hole | Through-Hole | Through-Hole | Surface Mount |
Principaux différenciateurs
- Drop-in 28-pin PDIP compatibility across all temperature grades (vs AD7878JNZ)
- Integrated 8-word FIFO decouples ADC from DSP read timing (vs AD7862AR-10)
- On-chip 3 V Zener reference eliminates external reference IC (vs AD7265BCPZ-REEL)
Notes de conception
Place a 1 microfarad decoupling capacitor as close as possible to the VDD analog supply pin (pin 27) and another on the VLOGIC digital supply pin (pin 28). Use separate analog and digital ground planes tied together at a single point near the ADC to keep digital switching noise out of the analog input path. The +5 V analog supply should be low-noise and post-LDO to keep reference and conversion accuracy intact.
Route the analog input trace on a separate analog layer, away from the parallel digital data bus (D0-D11) and the DSP control strobes (CS, RD, WR). Place the anti-alias low-pass filter within 10 mm of the VIN pin to limit sampled noise. Add a small RC network (10 ohm + 100 pF) at the converter input to dampen amplifier-induced ringing without degrading settling.
Do not drive the analog input with a high-impedance source; the 2 microsecond track-and-hold acquisition time requires the source to settle within the acquisition window. Ensure the BUSY signal is correctly interpreted by the DSP - active-high conversion-busy polarity is easy to invert. The 3 V internal Zener reference must be bypassed with the recommended capacitor value, or the noise performance degrades significantly.
Maintain short, impedance-controlled traces for CS, RD, and WR strobes to prevent timing-violation read errors at full 100 kHz throughput. The DSP interface is designed for high-speed hosts, so any extra capacitive loading on the data bus can corrupt reads. Buffer the data bus if more than one DSP or peripheral shares the parallel bus, and add 22 ohm series resistors near the driver outputs.
Informations de conformité
AD7878LN in the original PDIP package is not lead-free (standard PDIP). RoHS-compliant alternative is AD7878LNZ in the same 28-pin PDIP footprint. Not AEC-Q100 qualified - industrial-grade only.
