AD7822BN

Overview

The AD7822BN is an 8-bit, single-channel analog-to-digital converter (ADC) from the ADI AD7822 series. 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 parameters include a signal-to-noise ratio of 48 dB minimum, integral nonlinearity of ±0.75 LSB max, and differential nonlinearity of ±0.75 LSB max. It includes an internal 2.5 V reference and supports flexible parallel interfacing.

Feature Summary

• Half-flash ADC architecture providing fast conversion times suitable for real-time DSP processing.
• On-chip track-and-hold amplifier capable of handling full-scale input signals up to 10 MHz.
• Automatic power-down mode at the end of conversion to minimize power consumption.
• Input offset adjustment via VMID pin to center the analog input span within the supply range.

Applications

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

Procurement Notes

Verify the specific package variant required, as the AD7822 family is available in multiple packages including PDIP-20, SOIC-20, and TSSOP-20. Confirm that the 'B' suffix denotes the industrial temperature range (-40°C to +85°C). Ensure compatibility with the target microprocessor interface logic levels before ordering.

Selection Notes

Select the AD7822BN when a single-channel, high-speed 8-bit conversion is needed. Compare against AD7825 (4 channels) and AD7829 (8 channels) if multi-channel sampling is required. Consider the 3V vs 5V supply requirements and whether the internal 2.5V reference meets system accuracy needs without external components.

Part Context

The AD7822BN belongs to the AD7822/AD7825/AD7829 family of high-speed, microprocessor-compatible ADCs. These devices share a common half-flash architecture and interface timing but differ in channel count. The AD7822 specifically provides one single-ended analog input channel, making it distinct from its four-channel and eight-channel counterparts.

Replacement Considerations

Direct functional replacements within the same family include the AD7825 (4-channel) and AD7829 (8-channel), though pin counts and channel configurations differ. For single-channel applications, verify if legacy parts like the AD7821 are suitable, noting potential differences in speed and interface protocols.

FAQ

How does the AD7822 handle power-down?

The AD7822 features automatic power-down at the end of a conversion. If the CONVST pin is logic low when the EOC signal goes high, the device enters power-down mode. A separate PD pin can also be used to manually force power-down.

What is the function of the VMID pin?

The VMID pin allows the user to adjust the input offset. By applying a voltage to this pin, the analog input span can be centered anywhere within the AGND to VDD range, which helps accommodate system offsets or single-supply op amp limitations.

Can the AD7822 operate standalone?

Yes, the flexible parallel interface with the EOC pulse allows the AD7822 to be used in a standalone manner without continuous microprocessor intervention, facilitating independent operation.