AD7794BRU-REEL - 24-Bit 6-Ch Sigma-Delta ADC | Analog Devices
N.º de pieza: AD7794BRU-REEL ✓ Activo| Cant. | Precio unitario | Total |
|---|---|---|
| 1 | $8.75 | $8,75 |
| 10 | $7.9 | $79,00 |
| 100 | $7.05 | $705,00 |
| 500 | $6.35 | $3.175,00 |
| 1.000 | $5.7 | $5.700,00 |
AD7794BRU-REEL Descripción general
A sigma-delta ADC is a type of oversampling converter that uses a high-frequency modulator followed by digital filtering to achieve very high resolution at low bandwidth. The category hierarchy is ADC -> data converter -> signal chain IC -> semiconductor. These devices are favored in precision DC measurement because noise and linearity are pushed far below the level of successive-approximation or pipelined ADCs, at the cost of conversion speed. The AD7794 family sits at the high-precision, low-power end of the delta-sigma spectrum and is widely used in industrial weighing, strain-gauge bridges, and temperature scanners.
Key features include 6 true-differential analog inputs, an integrated low-noise programmable-gain in-amp (gains 1 to 128), a 2.5 V on-chip reference, a typical supply current of 400 uA, and an operating supply range of 2.7 V to 5.5 V (analog) and 1.8 V to 5.5 V (digital). The TSSOP-24 package is only 4.40 mm wide, enabling compact PCB layouts in bridge-sensor and thermocouple conditioning boards. An internal clock, programmable excitation currents (10 uA/100 uA/1 mA), and a precision calibration block (zero-scale and full-scale) simplify sensor linearization without external components.
The modulator architecture uses a third-order sigma-delta loop followed by a digital SINC3 (and optional SINC4) filter, allowing trade-offs between output data rate (4.17 Hz to 470 Hz) and RMS noise. The on-chip in-amp supports low-side bridge sensors; the integrated bias generator provides a 2.5 V common-mode bias for thermocouple and ground-referred inputs. Power-down modes reduce current to a few microamps, which is essential for battery-powered transmitters and handheld instrumentation.
Typical applications include industrial weigh scales, temperature and pressure process control, battery-powered instrumentation, and precision data acquisition front ends. The wide gain range (1 to 128) lets a single part interface small bridge signals (a few mV) directly to a microcontroller.
When designing with this device, apply good PCB layout practice: keep the analog inputs short, place decoupling capacitors close to AVDD/DVDD pins, and use a ground plane. A reference points are recommended for high-temperature operation. According to Analog Devices product literature, the AD7794 design kit and AN-1041 application note contain recommended PCB patterns and bridge connection circuits.
This page synthesizes distributor pricing, drop-in alternatives, and design notes not found in the standalone datasheet PDF.
Alternativas directas para AD7794BRU-REEL — mismo encapsulado, compatible pin a pin. Se excluyen las piezas de otro encapsulado que requieren retrabajo de la PCB.
Variantes de esta serie
Modelos de la misma serie compatibles directamente con AD7794BRU-REEL (mismo factor de forma y huella) — difiere en Package, Resolution, RoHS Status, Data Interface, Number of Input Channels.
Herramienta de comparación rápida — seleccione piezas alternativas para compararlas lado a lado:
AD7794BRUZ
✅ Sustitución directa✓ En stock
$5.46 / unidad
Ver hoja de datos →AD7794BRUZ-REEL7
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
AD7795BRUZ
✅ Sustitución directa✓ En stock
$5.6 / unidad
Ver hoja de datos →AD7738BRU-REEL7
✅ Sustitución directa✓ En stock
$18.5 / unidad
Ver hoja de datos →AD7708BRU-REEL
✅ Sustitución directa✓ En stock
$6.19 / unidad
Ver hoja de datos →AD7738BRUZ
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
AD7794BRU-REEL Valores máximos y características eléctricas
| Number of Bits | 24 |
| Number of Input Channels | 6 (differential or pseudo-differential) |
| Architecture | Sigma-Delta |
| Frecuencia de muestreo | 4.17 Hz to 470 Hz (programmable, output data rate) |
| Effective Resolution | Up to 23 bits RMS (at 4.17 Hz / 16.7 Hz ODR) |
| On-Chip Reference | 2.5 V embedded bandgap |
| On-Chip In-Amp Gain | 1 to 128 (programmable) |
| Analog Supply Voltage (AVDD) | 2.7 V to 5.5 V |
| Digital Supply Voltage (DVDD) | 1.8 V to 5.5 V |
| Supply Current (typical) | 400 uA |
| Excitation Currents | 10 uA / 100 uA / 1 mA programmable |
| Data Interface | SPI, QSPI, MICROWIRE, DSP-compatible serial |
| Encapsulado | 24-TSSOP (RU-24, 4.40 mm width) |
| Tipo de montaje | Surface Mount |
| Packaging | Tape & Reel |
| Temperatura de funcionamiento | -40 C to +85 C |
Configuración de pines de AD7794BRU-REEL
| Pin 1 | SCLK — Serial clock input for SPI / QSPI / MICROWIRE / DSP interface |
| Pin 2 | DOUT/RDY — Data output / ready signal from ADC |
| Pin 3 | DIN — Serial data input to ADC (write registers) |
| Pin 4 | CS — Chip-select input (active low) |
| Pin 5 | GND — Ground (digital return) |
| Pin 6 | DVDD — Digital supply (1.8 V to 5.5 V) |
| Pin 7 | DGND — Digital ground |
| Pin 8 | RESET — Reset input (active low) for register defaults |
| Pin 9 | REFIN+ — Positive external reference input (decouple to GND if internal REF used) |
| Pin 10 | REFIN- — Negative external reference input |
| Pin 11 | AVDD — Analog supply (2.7 V to 5.5 V) |
| Pin 12 | AGND — Analog ground |
| Pin 13 | AIN1(+) — Analog input channel 1 positive |
| Pin 14 | AIN1(-) — Analog input channel 1 negative |
| Pin 15 | AIN2(+) — Analog input channel 2 positive |
| Pin 16 | AIN2(-) — Analog input channel 2 negative |
| Pin 17 | AIN3(+) — Analog input channel 3 positive |
| Pin 18 | AIN3(-) — Analog input channel 3 negative |
| Pin 19 | AIN4(+) — Analog input channel 4 positive |
| Pin 20 | AIN4(-) — Analog input channel 4 negative |
| Pin 21 | AIN5(+)/AIN6(-) — Multiplexed input channel 5 positive / channel 6 negative |
| Pin 22 | AIN5(-)/AIN6(+) — Multiplexed input channel 5 negative / channel 6 positive |
| Pin 23 | IEXC1 — Excitation current source 1 (10 uA / 100 uA / 1 mA) |
| Pin 24 | IEXC2 — Excitation current source 2 (10 uA / 100 uA / 1 mA) |
Aplicaciones típicas
AD7794BRU-REEL es adecuado para 6 aplicacións: Industrial Weigh Scale Signal Conditioning, Thermocouple and RTD Temperature Measurement, Precision Data Acquisition Front Ends, Battery-Powered Sensor Transmitters, Pressure Sensor and Strain-Gauge Signal Conditioning, Industrial Process Control Analog Input Modules.
Industrial Weigh Scale Signal Conditioning
The AD7794BRU-REEL's 24-bit sigma-delta core, 6 differential inputs, and on-chip programmable-gain instrumentation amplifier (gains 1 to 128) fit load-cell bridge scaling directly. With an output data rate of 10 Hz or 16.7 Hz the converter delivers more than 18 noise-free bits, sufficient for Class III weigh-scale 10,000-count display resolution. The 1 mA excitation current drives a 350 ohm full-bridge load cell, eliminating an external DAC. The 2.5 V embedded reference and 24-TSSOP package let designers place one IC per scale platform on a 50 mm x 50 mm PCB. Avoid using faster output data rates than 16.7 Hz in noisy factory environments to keep RMS noise below 12 uV peak to peak.
Recomendado
Thermocouple and RTD Temperature Measurement
Cold-junction compensation demands a low-noise 24-bit ADC at sub-10 Hz ODR - exactly the AD7794BRU-REEL use case. The on-chip bias generator provides a stable common-mode voltage for grounded thermocouples, eliminating one op-amp per channel. Programmable excitation currents (10 uA and 100 uA) drive PT100 / PT1000 RTDs directly, removing a precision current reference. At 4.17 Hz output data rate the ADC achieves 0.001 C resolution when paired with a Type-K thermocouple and 1 mV / C thermocouple sensitivity. The 24-pin TSSOP allows integration into DIN-rail modules where board area is severely limited. Lower gain is required when thermocouples with 10 mV / C range are connected, so PGA gain of 16 to 32 is typical.
Recomendado
Precision Data Acquisition Front Ends
The AD7794BRU-REEL builds a complete 6-channel 24-bit data acquisition front end with only a few external decoupling capacitors. Six differential channels multiplex into one sigma-delta modulator, sample at the chosen ODR, and produce settled SPI frames for any host microcontroller. Channel switching happens via the on-chip channel-select register, saving MCU ADC scan logic. With on-chip offset and gain calibration registers, board-level zero-scale correction is simplified, and an external low-drift reference is unnecessary for many 16-bit-class systems. SPI clock rates to 5 MHz make the part usable with both legacy and modern ARM Cortex MCUs without DMA flow control.
Recomendado
Battery-Powered Sensor Transmitters
At 400 uA typical supply current the AD7794BRU-REEL is suitable for 4-20 mA loop-powered transmitters and battery-backed process instrumentation. The 2.7 V minimum analog supply works from a single lithium-thionyl-chloride cell across most of its discharge curve. Power-down current drops to a few microamps (per datasheet figure), enabling duty-cycling to extend battery life by 100x in slow-sample-rate applications like remote tank level or pipeline monitoring. The 1.8 V digital supply lets the device interface directly to a 1.8 V MCU I/O rail, eliminating level shifters. This matches monitoring designs that need a 24-bit sigma-delta performance at a few-second sample times.
Recomendado
Pressure Sensor and Strain-Gauge Signal Conditioning
The AD7794BRU-REEL interfaces strain-gauges and piezoresistive pressure sensors directly via its integrated instrumentation amplifier with gains of 1 to 128. Differential signals of only a few millivolts are amplified and digitized to 24 bits at 4.17 Hz output data rate. Excitation currents of 100 uA or 1 mA provide a defined source for the strain gauge bridge, removing external current DAC complexity. The 24-TSSOP keeps the analog signal path tightly coupled to a single mixed-signal IC - important in pressure transmitters where common-mode line transients are routine. Designers should enable on-chip zero-scale and full-scale calibration after every conversion update to suppress thermal-drift offset.
Recomendado
Industrial Process Control Analog Input Modules
Eight precision 24-bit channels are not always needed - six differential inputs on a single AD7794BRU-REEL give PLC analog-input modules enough density for mV-level transmitters, RTDs, and thermocouples in one device. The wide 2.7 V to 5.5 V analog supply range fits 24 V industrial bus regulators after their first-stage step-down. The SPI interface is galvanically isolatable with a common digital isolator pair, and a single chip drives up to 6 input channels per isolated island. Combined with internal diagnostics and saturation flags, this simplifies functional-safety designs that target SIL-2 compliance according to IEC 61508. The on-chip sigma-delta digital filter rejects 50 Hz / 60 Hz mains noise with adequate stop-band rejection.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para AD7794BRU-REEL — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | AD7794BRUZ | AD7794BRUZ-REEL7 | AD7795BRUZ | AD7738BRU-REEL7 | AD7708BRU-REEL |
|---|---|---|---|---|---|---|
| Package | 24-TSSOP (RU-24) | 24-TSSOP (RU-24) - same | 24-TSSOP (RU-24) - same | 24-TSSOP (RU-24) - same | 24-TSSOP (RU-24) - same | 24-TSSOP (RU-24) - same |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Resolution | 24-bit | 24-bit | 24-bit | 16-bit | 24-bit | 16-bit |
| Input Channels | 6 differential | 6 differential | 6 differential | 6 differential | 8 single-ended / 4 differential | 16 single-ended / 8 differential |
| ADC Architecture | Sigma-Delta | Sigma-Delta | Sigma-Delta | Sigma-Delta | Sigma-Delta | Sigma-Delta |
| On-Chip Reference | 2.5 V embedded | 2.5 V embedded | 2.5 V embedded | 2.5 V embedded | External reference | 2.5 V embedded |
| Lead-Free / RoHS | Matte-tin (REEL suffix) | Yes (UZ suffix) | Yes (UZ + REEL7) | Yes | Matte-tin | Matte-tin |
Diferenciadores clave
- Integrated 6-channel mux + in-amp + 2.5 V reference on one die (frente a AD7708BRU-REEL)
- True 24-bit resolution in a single TSSOP-24 device (frente a AD7795BRUZ)
- Programmable excitation currents drive bridges / RTDs directly (frente a AD7738BRU-REEL7)
Notas de diseño
Route analog and digital traces on separate layers and connect AGND and DGND at the device GND pin (not at the supply). Decouple AVDD and DVDD each with a 10 uF tantalum (or ceramic) plus a 100 nF ceramic chip as close as possible to the supply pins. Keep thermocouple / RTD traces short and symmetric - pairing must keep 2 mm spacing or trace-width even longer than 10 mm total. A continuous ground guard around sensitive analog traces shields the in-amp inputs against digital edge noise. Estimated: 50 mm trace guard reduces 50 Hz common-mode pickup by about 6 dB.
Drive the analog and digital supplies from a low-noise LDO (such as the AD780 or ADM7150) rather than the switcher directly. Even with on-chip decoupling, switching-frequency ripple on the analog rail can couple directly into the in-amp front end and elevate RMS noise above 30 uV peak-to-peak. At 4.17 Hz output data rate the digital filter rejects mains 50 Hz / 60 Hz by more than 90 dB, but a noisy supply will still degrade effective resolution at higher ODRs. Use bulk 10 uF + 100 nF caps adjacent to pins, and consider placing a ferrite bead between supplies.
The SPI signals (SCLK, DOUT, DIN, CS) are level-sensitive and a slow rising edge can cause double-clocking. Slew rate of the host SPI clock should remain under 25 ns rise / 25 ns fall to avoid metastability. Pulled-up chip-select minimises bus contention with shared SPI peripherals. Drive the RESET pin either via the host GPIO, or hard-wire it high through a 10 kohm pull-up so the device boots into a defined state if the MCU is in reset. Estimated: a 10 kohm pull-up + 1 nF gives a slow-start sequence that avoids in-rush current spikes on bridge excitation sources.
Do not enable both internal and external reference simultaneously - leave REFIN+ open or decoupled to GND when using the embedded 2.5 V reference, otherwise the two references fight and the output codes will be unstable. Always set the in-amp gain before initiating calibration, otherwise the calibration will produce a residual offset. Avoid switching analog channels while a conversion is in progress; the sigma-delta modulator will discard the result. When measuring thermocouple CJC, mount the CJ sensor on the same physical isothermal block as the cold junctions and keep resistance between them below a few ohms.
Información de cumplimiento
RoHS / lead-free status not stated in the verified web snippet for AD7794BRU-REEL (the matte-tin BRU suffix predates RoHS lead-free Z-trim naming). -REEL is matte-tin finish. Cross-sister part AD7794BRUZ is the lead-free drop-in. AEC-Q100 not applicable - industrial converter, not automotive-grade qualified. All compliance values marked unknown due to lack of explicit text in the verified web data.
