AD7781BRUZ - 20-Bit Low Power Sigma-Delta ADC | Analog Devices
MPN: AD7781BRUZ ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $8.42 | $8.42 |
| 10 | $7.58 | $75.80 |
| 100 | $6.74 | $674.00 |
| 500 | $5.9 | $2,950.00 |
| 1,000 | $5.06 | $5,060.00 |
AD7781BRUZ Overview
An analog-to-digital converter (ADC) is an electronic component that converts continuous analog signals into discrete digital numbers. The AD7781 is a sigma-delta ADC, which uses oversampling and noise shaping to achieve high resolution (20 bits) at low bandwidths. It belongs to the family of precision data converters used in measurement and instrumentation systems, where accurate conversion of sensor signals is critical. The on-chip PGA allows direct connection of low-level bridge sensors without external amplification, simplifying the signal chain.
Key features of the AD7781BRUZ include 20-bit resolution, a pin-programmable gain of 1, 8, 16, 32, 64, or 128, and a maximum output data rate of 16.7 SPS. It has a differential input, external reference, and a serial SPI-compatible interface. The device includes a power-down mode that reduces current consumption to 1 μA, extending battery life in portable designs. The on-chip oscillator eliminates the need for an external clock, reducing component count and board space.
The AD7781 uses a sigma-delta modulator followed by a digital filter, achieving excellent noise performance for low-frequency measurements. The programmable gain amplifier (PGA) amplifies small sensor signals before conversion, improving effective resolution. The device operates over the industrial temperature range of -40°C to +105°C, ensuring reliable performance in harsh environments. The 16-lead TSSOP package is compact and suitable for space-constrained designs.
Typical applications include weigh scales, strain gage transducers, pressure sensors, and other bridge-type sensors. The low power consumption and high resolution make it suitable for portable medical devices, industrial process control, and battery-powered instrumentation. The AD7781BRUZ is a drop-in replacement for the AD7781BRZ (SOIC package) with the same electrical specifications, but in a smaller TSSOP footprint.
When designing with the AD7781BRUZ, ensure that the reference voltage is stable and low-noise, as it directly affects conversion accuracy. Use a precision reference such as the ADR4520 for best performance. The differential inputs should be driven by a low-impedance source to minimize settling time errors. Proper PCB layout with a solid ground plane and decoupling capacitors near the supply pins is essential for achieving the specified noise performance.
Drop-in alternatives for AD7781BRUZ — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with AD7781BRUZ (same form factor and footprint) — differing in Resolution, Supply Current, Package, Supply Voltage, Number of Channels.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
AD7781BRUZ-REEL
✅ Drop-In📋 Reference alternative (not in catalog)
AD7781CRZ-REEL
✅ Drop-In📋 Reference alternative (not in catalog)
AD7781BRUZ-REEL7
✅ Drop-In📋 Reference alternative (not in catalog)
AD7781CRUZ
✅ Drop-In📋 Reference alternative (not in catalog)
AD7781BRUZ Maximum Ratings & Electrical Characteristics
| Resolution | 20 bit |
| Number of Channels | 1 |
| Input Type | Differential |
| Architecture | Sigma-Delta |
| Data Interface | SPI |
| Sampling Rate | 16.7 SPS |
| Programmable Gain | 1, 8, 16, 32, 64, 128 |
| Supply Voltage | 2.7 V to 5.25 V |
| Current Consumption | 330 μA |
| Power-Down Current | 1 μA |
| Reference Type | External |
| Operating Temperature Range | -40°C to +105°C |
| Package | 16-TSSOP |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
AD7781BRUZ Pin Configuration
| Pin 1 | SCLK — Serial clock input |
| Pin 2 | DIN — Serial data input |
| Pin 3 | DOUT — Serial data output |
| Pin 4 | CS — Chip select (active low) |
| Pin 5 | GND — Ground |
| Pin 6 | AVDD — Analog power supply |
| Pin 7 | VREF — Reference voltage input |
| Pin 8 | AIN+ — Positive analog input |
| Pin 9 | AIN- — Negative analog input |
| Pin 10 | GND — Ground |
| Pin 11 | G0 — Gain select pin 0 |
| Pin 12 | G1 — Gain select pin 1 |
| Pin 13 | G2 — Gain select pin 2 |
| Pin 14 | PDRST — Power-down and reset |
| Pin 15 | DVDD — Digital power supply |
| Pin 16 | DOUT/RDY — Data output / ready |
Typical Applications
AD7781BRUZ is suitable for 6 applications: Weigh Scales, Strain Gage Transducers, Pressure Sensors, Portable Medical Devices, Industrial Process Control, Battery-Powered Instrumentation.
Weigh Scales
The AD7781BRUZ is ideal for weigh scale applications due to its 20-bit resolution and on-chip PGA with gain up to 128. It directly interfaces with load cells, providing accurate weight measurements. The low power consumption (330 μA) makes it suitable for battery-operated scales. The differential input rejects common-mode noise, ensuring stable readings in industrial environments. The 16.7 SPS output rate is sufficient for static weight measurements, and the power-down mode extends battery life between measurements.
Recommended
Strain Gage Transducers
The AD7781BRUZ is designed for strain gage transducers, providing high-resolution conversion of small differential signals. The on-chip PGA amplifies the low-level bridge output, eliminating the need for external instrumentation amplifiers. The device's low noise performance ensures accurate strain measurements. The SPI interface allows easy connection to microcontrollers. The wide supply voltage range (2.7V to 5.25V) accommodates various system power rails. The compact TSSOP package saves board space in transducer modules.
Recommended
Pressure Sensors
The AD7781BRUZ is well-suited for pressure sensor applications, converting the small output of a bridge-type pressure sensor into a digital signal. Its 20-bit resolution provides high accuracy, and the programmable gain allows optimization for different sensor sensitivities. The low power consumption is critical for portable pressure monitors. The device's on-chip oscillator reduces external component count. The industrial temperature range (-40°C to +105°C) ensures reliable operation in harsh environments. The SPI interface simplifies data transfer to a host processor.
Recommended
Portable Medical Devices
The AD7781BRUZ is suitable for portable medical devices such as blood pressure monitors and glucose meters, where low power and high resolution are essential. The 330 μA current consumption extends battery life, and the power-down mode further reduces power when not measuring. The small TSSOP package fits compact medical device PCBs. The differential input and PGA allow direct connection to medical sensors. The SPI interface enables integration with low-power microcontrollers. The device's accuracy meets the requirements of medical measurement standards.
Recommended
Industrial Process Control
The AD7781BRUZ is used in industrial process control for monitoring pressure, temperature, and flow. Its high resolution and low noise ensure accurate process measurements. The device's differential input rejects common-mode interference from motors and other industrial equipment. The wide operating temperature range allows deployment in factory floors. The SPI interface connects to PLCs and industrial controllers. The on-chip PGA eliminates the need for external signal conditioning, reducing system cost. The 16.7 SPS data rate is adequate for most process control loops.
Recommended
Battery-Powered Instrumentation
The AD7781BRUZ is ideal for battery-powered instrumentation, such as handheld data loggers and portable test equipment. Its low power consumption (330 μA) and power-down mode (1 μA) maximize battery life. The wide supply voltage range allows operation from a single lithium-ion cell or two alkaline batteries. The small TSSOP package is suitable for compact handheld devices. The SPI interface enables low-power microcontrollers to read data efficiently. The device's high resolution ensures accurate measurements in portable applications.
Recommended
Recommended Products Summary
Engineering reference data for AD7781BRUZ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AD7781BRZ | AD7781BRUZ-REEL | AD7781CRZ-REEL |
|---|---|---|---|---|
| Package | 16-TSSOP | 16-SOIC | 16-TSSOP | 16-TSSOP |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Resolution | 20 bit | 20 bit | 20 bit | 20 bit |
| Sampling Rate | 16.7 SPS | 16.7 SPS | 16.7 SPS | 16.7 SPS |
| Supply Voltage | 2.7V to 5.25V | 2.7V to 5.25V | 2.7V to 5.25V | 2.7V to 5.25V |
| Current Consumption | 330 μA | 330 μA | 330 μA | 330 μA |
| Operating Temperature | -40°C to +105°C | -40°C to +105°C | -40°C to +105°C | -40°C to +125°C |
| Packaging | Tube | Tube | Tape & Reel | Tape & Reel |
Key Differentiators
- Low power consumption of 330 μA (vs AD7799BRUZ)
- Pin-programmable gain up to 128 (vs AD7190BRUZ)
- Smaller TSSOP package (vs AD7781BRZ)
Design Notes
The AD7781BRUZ operates from 2.7V to 5.25V. Use a low-noise LDO regulator to supply AVDD and DVDD. Decouple each supply pin with a 0.1μF ceramic capacitor placed close to the pin, and a 10μF tantalum capacitor for bulk decoupling. Ensure the ground plane is solid and connected to the exposed pad if present.
For optimal noise performance, place the AD7781BRUZ away from switching regulators and digital circuits. Use a ground plane under the device and route analog and digital signals separately. Keep the reference input (VREF) trace short and shielded. Use a 4-layer PCB with dedicated power and ground planes for best results.
Do not leave the gain select pins (G0, G1, G2) floating; tie them to DVDD or GND to set the desired gain. Ensure the reference voltage is stable and within the specified range. Avoid driving the analog inputs beyond the supply rails. Use a series resistor (e.g., 1kΩ) on the SCLK line to reduce ringing if the SPI bus is long.
Compliance Information
RoHS compliant per Analog Devices product page. Not AEC-Q100 qualified. Lead-free finish.
