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Analog Devices Inc. AD7781CRUZ-REEL
- Part No.:
- AD7781CRUZ-REEL
- Manufacturer:
- Analog Devices Inc.
- Category:
- Analog to Digital Converters (ADC)
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
AD7781CRUZ-REEL.pdf
- Description:
- IC ADC 20BIT SIGMA-DELTA 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,461
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Product details
Overview
AD7781CRUZ-REEL from Analog Devices is a 20-bit, pin-programmable, low-power sigma-delta ADC optimized for bridge sensor front ends. It integrates a programmable gain amplifier (gain = 1 or 128), on-chip oscillator, and bridge power-down switch. With 115 μA typical current at gain = 1 and simultaneous 50 Hz/60 Hz rejection, it serves precision weigh scales and portable instrumentation.
For engineers reviewing the AD7781CRUZ-REEL datasheet, AD7781CRUZ-REEL pinout, AD7781CRUZ-REEL application, or AD7781CRUZ-REEL equivalent, key selection criteria include update rate (10 Hz / 16.7 Hz), RMS noise (44 nV at gain = 128, 10 Hz), p-p resolution (17.6 bits), ±6 ppm FSR INL, and dual-supply operation (AVDD: 2.7–5.25 V, DVDD: 2.7–5.25 V).
Technical Context
The AD7781CRUZ-REEL implements a 20-bit sigma-delta modulator with digital filtering selectable via the FILTER pin (10 Hz high-rejection or 16.7 Hz fast-settling). Its PGA supports differential input ranges of ±5 V (gain = 1) or ±39 mV (gain = 128), referenced to an external REFIN(+)–REFIN(−) voltage up to AVDD.
It uses a 2-wire read-only serial interface with Schmitt-triggered SCLK and dual-function DOUT/RDY (data ready + serial output). The internal bridge power-down switch (RON ≤ 9 Ω, 30 mA rating) is controlled by PDRST, enabling full system power gating in battery-operated load cell systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Resolution | 20-bit sigma-delta ADC with no missing codes guaranteed |
| Update Rate | 10 Hz (300 ms settling) or 16.7 Hz (120 ms settling), selected by FILTER pin |
| RMS Noise | 44 nV (C grade, gain = 128, 10 Hz, 3 V ref); enables sub-μV-level signal detection |
| Integral Nonlinearity | ±6 ppm FSR - ensures <0.0006% full-scale error in precision weighing |
| Power Supply Range | AVDD: 2.7–5.25 V; DVDD: 2.7–5.25 V - supports mixed-voltage digital interfaces |
| Operating Temp | −40°C to +105°C - qualified for industrial and automotive-adjacent environments |
| Common-Mode Rejection | 110 dB at 50/60 Hz - eliminates line-frequency interference without external notch filters |
Pinout & Package
AD7781CRUZ-REEL is supplied in a 16-lead TSSOP package (RoHS-compliant, moisture sensitivity level 3). Pin functions are fully defined and validated per Analog Devices Rev. 0 datasheet Figures 7 and Table 6.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SCLK | Serial clock input | Schmitt-triggered; controls timing of 32-bit read cycles (20-bit data + 8 status bits) |
| DOUT/RDY | Dual-function output | Active-low data-ready flag and serial data output; tristated during PDRST low |
| GAIN | Gain select control | Low = gain 128 (±39 mV FS); high = gain 1 (±5 V FS); resets modulator on change |
| FILTER | Filter response select | Low = 16.7 Hz (120 ms settling); high = 10 Hz (300 ms, >−45 dB stopband attenuation) |
| PDRST | Power-down/reset | Active-low; powers down ADC, opens BPDSW, resets logic, and tristates DOUT/RDY |
| BPDSW | Bridge power-down switch terminal | Connects to low-side of bridge sensor; closed when PDRST = high (RON ≤ 9 Ω) |
| AIN(+), AIN(−) | Differential analog input | High-impedance inputs; support direct connection to strain gages and load cells |
| REFIN(+), REFIN(−) | Differential reference input | Unbuffered; accepts 0.5 V to AVDD reference; enables ratiometric bridge measurements |
Key Features
| Feature | Design Value |
|---|---|
| Pin-programmable filter and gain | Eliminates firmware configuration overhead; enables hardware-selectable trade-offs between speed (16.7 Hz) and noise rejection (10 Hz) |
| Simultaneous 50 Hz/60 Hz rejection | 63–90 dB attenuation at both update rates - removes mains interference without software calibration or external filters |
| Bridge power-down switch (BPDSW) | 9 Ω RON, 30 mA rating - disconnects excitation from load cell during idle, reducing system current by ~15 mA in 5 V systems |
| Independent AVDD/DVDD supplies | Allows 3.3 V digital interface with 5 V analog supply - simplifies mixed-voltage PCB design and improves noise isolation |
| Status-bit appended reads | 8 status bits per 32-bit transfer - provide pattern validation of serial integrity and conversion validity without additional protocol overhead |
Applications
| Industrial Weigh Scales | Pressure Transducers |
|---|---|
Use Scenario: High-accuracy platform scales measuring 0–300 kg with 1 g resolution under varying ambient temperature. IC Role / Device Role / Timing Role: Primary 20-bit ADC front end; digitizes mV-level output from 4-wire load cell bridges with integrated PGA and ratiometric reference handling. Use Value: 44 nV RMS noise and ±6 ppm INL enable stable 1 g resolution across −40°C to +105°C without recalibration; BPDSW extends battery life by disabling bridge excitation between readings. |
Use Scenario: Battery-powered HVAC pressure sensors monitoring duct static pressure (0–100 Pa) with 0.1 Pa resolution. IC Role / Device Role / Timing Role: Low-power sigma-delta converter interfacing to piezoresistive pressure bridge; uses 10 Hz filter mode for mechanical vibration rejection. Use Value: 300 ms settling at 10 Hz suppresses low-frequency mechanical resonance; 115 μA quiescent current allows multi-year operation on coin-cell batteries. |
| Portable Load Cell Testers | Process Control Transmitters |
Use Scenario: Handheld calibrator verifying load cell linearity and zero drift in field service applications. IC Role / Device Role / Timing Role: Precision ADC with user-selectable gain (1/128) and update rate (10/16.7 Hz) for rapid verification across multiple sensor sensitivities. Use Value: Hardware pin control eliminates boot-time configuration delays; offset binary coding simplifies real-time display of signed differential voltage values. |
Use Scenario: 4–20 mA loop-powered transmitter for tank level monitoring in chemical plants. IC Role / Device Role / Timing Role: Isolated analog front end; digitizes bridge output and feeds microcontroller for HART communication and diagnostics. Use Value: −40°C to +105°C rating and 110 dB CMRR at 50/60 Hz ensure reliable operation in electrically noisy industrial enclosures without external shielding. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 20-bit sigma-delta ADC applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD7170BRUZ | 24-bit resolution, 10–120 SPS, SPI interface, no integrated PGA or BPDSW | Higher resolution but requires external amplification and bridge switching circuitry | Choose AD7170BRUZ only if 24-bit resolution is mandatory and board space permits added components |
| ADS1232IPW | 20-bit, PGA (1–128), 10–80 SPS, integrated oscillator, but no BPDSW or simultaneous 50/60 Hz rejection | Lacks hardware-based mains rejection and bridge power gating - requires external filtering and discrete MOSFET control | Prefer ADS1232IPW only when pin count is constrained and system-level power management is already implemented |
Compared with AD7781CRUZ-REEL, AD7170BRUZ offers higher resolution but increases BOM cost and layout complexity, while ADS1232IPW lacks the integrated BPDSW and simultaneous 50/60 Hz rejection-critical for battery life and EMI robustness in weigh scale designs.
Availability
AD7781CRUZ-REEL is available at Aetrix Electronics and suitable for industrial weigh scales, pressure transducers, and portable instrumentation requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.
Supply support for AD7781CRUZ-REEL includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.
The AD7781CRUZ-REEL belongs to Analog Devices' precision sigma-delta ADC product line, designed specifically for low-power, high-accuracy bridge sensor measurement in industrial and portable applications.
FAQ
What is the maximum allowed reference voltage for AD7781CRUZ-REEL?
The AD7781CRUZ-REEL accepts an external differential reference voltage (REFIN(+) – REFIN(−)) from 0.5 V up to AVDD. Absolute voltage limits are GND − 30 mV to AVDD + 30 mV per pin. For optimal performance with a 5 V AVDD, a 5 V reference is recommended - this maintains ratiometric accuracy when the same supply excites the bridge sensor.
Does AD7781CRUZ-REEL support true bipolar input signals?
AD7781CRUZ-REEL supports bipolar differential input voltage ranges (e.g., ±39 mV at gain = 128), but does not accept negative voltages relative to GND. The common-mode voltage must be ≥0.5 V, and absolute input limits are GND + 450 mV to AVDD − 1.1 V (gain = 128, FILTER = 0). Bipolar operation is achieved by referencing AIN(+) to AIN(−), not to system ground.
How does the BPDSW function in AD7781CRUZ-REEL, and what is its on-resistance?
The BPDSW in AD7781CRUZ-REEL is a low-side switch controlled by the PDRST pin: closed when PDRST is high, opened when PDRST is low. Its maximum on-resistance is 9 Ω, and it supports continuous current up to 30 mA. This allows direct disconnection of bridge sensor excitation to reduce system standby current - critical for battery-powered weigh scales.
Can AD7781CRUZ-REEL reject both 50 Hz and 60 Hz interference simultaneously?
Yes - AD7781CRUZ-REEL provides simultaneous 50 Hz and 60 Hz rejection at both 10 Hz and 16.7 Hz update rates, with normal-mode rejection ranging from 63 dB to 90 dB depending on grade and configuration. This is achieved through inherent notch characteristics of its digital filter architecture, eliminating need for external notch filters or software-based digital cancellation.
What is the purpose of the 8 status bits appended to each AD7781CRUZ-REEL data read?
Each 32-bit read from AD7781CRUZ-REEL includes 20 data bits followed by 8 status bits. These bits contain a fixed pattern sequence used to verify serial transfer integrity - confirming that the entire word was correctly shifted out and that no bit corruption occurred due to noise or timing violations on the 2-wire interface.
AD7781CRUZ-REEL Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Number of Bits:
- 20
- Sampling Rate (Per Second):
- 16.7
- Number of Inputs:
- 1
- Input Type:
- Differential
- Data Interface:
- SPI
- Configuration:
- PGA-ADC
- Ratio - S/H:ADC:
- -
- Number of A/D Converters:
- 1
- Architecture:
- Sigma-Delta
- Reference Type:
- External
- Voltage - Supply, Analog:
- 2.7V ~ 5.25V
- Voltage - Supply, Digital:
- 2.7V ~ 5.25V
- Features:
- PGA
- Operating Temperature:
- -40°C ~ 105°C
- Supplier Device Package:
- 16-TSSOP
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
AD7781CRUZ-REEL FAQ
1.How can I place an order for AD7781CRUZ-REEL through Aetrix?
Please submit a Request for Quotation (RFQ) for AD7781CRUZ-REEL on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for AD7781CRUZ-REEL reliable?
The price and inventory of AD7781CRUZ-REEL are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD7781CRUZ-REEL is usually 5 days.
3.What payment methods are accepted for AD7781CRUZ-REEL?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD7781CRUZ-REEL transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD7781CRUZ-REEL?
AD7781CRUZ-REEL orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD7781CRUZ-REEL order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for AD7781CRUZ-REEL?
For technical support, including AD7781CRUZ-REEL datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD7781CRUZ-REEL requirements.
6.How does Aetrix verify that AD7781CRUZ-REEL is sourced from the original manufacturer or authorized distributors?
All AD7781CRUZ-REEL products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that AD7781CRUZ-REEL meets industry standards.
7.What is the process for return or replacement of AD7781CRUZ-REEL?
All AD7781CRUZ-REEL units undergo pre-shipment inspection (PSI). If there is an issue with AD7781CRUZ-REEL, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The AD7781CRUZ-REEL part is unused and in its original packaging.
Return procedure for AD7781CRUZ-REEL:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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