Overview
The AD7781BRZ-REEL, produced by Analog Devices Inc., is a 20-bit, pin-programmable, ultralow power sigma-delta analog-to-digital converter (ADC). This device is particularly suited for low-frequency measurement applications, such as those involving bridge sensor systems. It is designed to consume very low power, making it ideal for portable or battery-operated products. The AD7781 features an on-chip programmable gain amplifier (PGA) and a digital filter, which provide high accuracy and noise rejection capabilities.
Key Specifications
| Parameter | Value |
|---|---|
| Resolution | 20 bits |
| Power Consumption | 330 μA |
| Power Supply Range | 2.7 V to 5.25 V |
| PGA Gain | 1 or 128 |
| Full-Scale Differential Input | ±5 V or ±39 mV |
| Output Data Rates | 10 Hz or 16.7 Hz |
| Settling Time | 120 ms (16.7 Hz), 300 ms (10 Hz) |
| Stop-Band Attenuation | Better than -45 dB at 10 Hz update rate |
| Package Options | 14-lead SOIC, 16-lead TSSOP |
Key Features
- Pin-programmable for ease of use, with dedicated pins controlling all features.
- On-chip PGA with gain options of 1 or 128.
- Low noise instrumentation amplifier and analog modulator.
- Digital filter with two filter response options for dynamic performance and stop-band attenuation.
- Simultaneous 50 Hz/60 Hz rejection at both output data rates.
- On-board clock, eliminating the need for an external clock.
- Power-down mode to switch off power to the bridge sensor and the AD7781 when not converting, enhancing battery life.
- Eight status bits appended to the 20-bit conversion data for serial transfer validation.
Applications
The AD7781 is primarily used in low-frequency measurement applications, including:
- Bridge sensor systems, such as load cells and pressure sensors.
- Portable or battery-operated devices where low power consumption is critical.
- Industrial automation and control systems requiring high precision and noise rejection.
Q & A
- What is the resolution of the AD7781 ADC?
The AD7781 has a resolution of 20 bits.
- What are the power consumption and power supply range of the AD7781?
The AD7781 consumes 330 μA and operates with a power supply range of 2.7 V to 5.25 V.
- What are the gain options of the on-chip PGA in the AD7781?
The on-chip PGA has gain options of 1 or 128.
- What are the output data rates of the AD7781?
The output data rates can be programmed to 10 Hz or 16.7 Hz.
- Does the AD7781 have any noise rejection features?
Yes, it provides simultaneous 50 Hz/60 Hz rejection at both output data rates and better than -45 dB stop-band attenuation at the 10 Hz update rate.
- What packages is the AD7781 available in?
The AD7781 is available in 14-lead SOIC and 16-lead TSSOP packages.
- How does the AD7781 enhance battery life in portable devices?
The AD7781 has a power-down mode that allows the user to switch off the power to the bridge sensor and the AD7781 when not converting, thus increasing battery life.
- What additional information is provided with each data read from the AD7781?
Eight status bits are appended to the 20-bit conversion data to confirm the validity of the serial transfer.
- Is an external clock required for the AD7781?
No, the AD7781 has an on-board clock, eliminating the need for an external clock.
- What type of applications is the AD7781 most suitable for?
The AD7781 is most suitable for low-frequency measurement applications, such as bridge sensor systems and portable or battery-operated devices.
