AD7822BNZ

Overview

The AD7822BNZ is an 8-bit, single-channel sampling analog-to-digital converter (ADC) from Analog Devices. It features a half-flash architecture with a maximum throughput of 2 MSPS and a conversion time of 420 ns. The device operates on a single supply voltage of either 3 V ± 10% or 5 V ± 10%. Key electrical specifications include a signal-to-noise ratio of 48 dB minimum at 30 kHz input frequency, integral nonlinearity of ±0.75 LSB, and differential nonlinearity of ±0.75 LSB. It incorporates an on-chip 2.5 V reference and a track-and-hold amplifier capable of handling full-scale input signals up to 10 MHz.

Feature Summary

• Half-flash ADC architecture providing fast 420 ns conversion times for real-time DSP processing.
• On-chip track-and-hold amplifier with high-frequency performance suitable for subsampling applications.
• Automatic power-down mode at the end of conversion to minimize power consumption.
• Flexible parallel interface with End-of-Conversion pulse allowing standalone operation.

Applications

• Data acquisition systems
• DSP front ends
• Disk drives
• Mobile communication systems
• Subsampling applications

Procurement Notes

Verify the specific package variant required, as the AD7822 series is available in multiple packages including PDIP-20, SOIC-20, and TSSOP-20. Confirm that the ordering suffix matches the desired mechanical footprint. Ensure compatibility with the target system's logic levels and supply voltage requirements before finalizing procurement.

Selection Notes

Select the AD7822BNZ when a single-channel, high-speed 8-bit conversion is required. Consider the AD7825 or AD7829 if multiple analog input channels are needed. Evaluate the power consumption against the application's throughput requirements, as the device offers automatic power-down capabilities. Ensure the input signal range aligns with the available 2 V or 2.5 V spans determined by the supply voltage.

Part Context

The AD7822 is part of the AD7822/AD7825/AD7829 family of high-speed, microprocessor-compatible 8-bit ADCs. This family shares a common half-flash architecture and functional block diagram, differing primarily in the number of analog input channels. The AD7822 specifically provides one channel, while the AD7825 offers four and the AD7829 offers eight channels.

Replacement Considerations

Direct pin-to-pin replacements within the same family include the AD7825 and AD7829, provided additional channels are acceptable. For single-channel applications, verify if other 8-bit, 2 MSPS ADCs from Analog Devices or competitors meet the specific timing and accuracy requirements without requiring schematic changes.

FAQ

How does the VMID pin affect the analog input range?

The VMID pin allows the user to center the analog input span anywhere between AGND and VDD. If left unconnected, the default input range is 0 V to 2.5 V for a 5 V supply or 0 V to 2 V for a 3 V supply.

What is the mechanism for automatic power-down?

The AD7822 automatically enters power-down mode at the end of a conversion if the CONVST pin is logic low when the End-of-Conversion (EOC) signal goes high.

Can the AD7822 operate in a standalone manner?

Yes, the flexible parallel interface includes an End-of-Conversion (EOC) pulse, which allows the ADC to be used in a standalone configuration without continuous microprocessor intervention.