Analog Devices Inc. AD7828CQ

Overview

AD7828CQ from Analog Devices is an 8-channel, 8-bit LC2MOS successive-approximation analog-to-digital converter with built-in track-and-hold, single 5 V supply operation, ±1/2 LSB total unadjusted error, and 2.5 µs per-channel conversion time. It digitizes 0 V to 5 V analog inputs across eight multiplexed channels and is used in real-time speech analysis, multichannel data acquisition, and industrial sensor monitoring systems.

For engineers reviewing the AD7828CQ datasheet, AD7828CQ pinout, AD7828CQ application, or AD7828CQ equivalent, key selection considerations include its 8-channel multiplexer address decoding (A0–A2), open-drain RDY/INT outputs, 28-pin PDIP package, differential reference interface (VREF(+) and VREF(–)), and compatibility with Z80, MC68000, and TMS32010 microprocessors without external clock generation.

Technical Context

The AD7828CQ employs a half-flash architecture using two 4-bit flash ADCs - one for MSBs and one for LSBs - with an internal 4-bit DAC to reconstruct and subtract the MSB approximation before LSB conversion. This eliminates need for external sampling clocks and enables inherent sample-and-hold behavior.

It supports two operational modes: Mode 0 (WAIT-state microprocessors) uses RDY to extend read cycles until conversion completes; Mode 1 (non-WAIT systems) reads prior result on first access and requires 2.5 µs inter-conversion delay. Address latching occurs on rising RD edge in Mode 1, while A0–A2 remain valid throughout CS/RD low in Mode 0.

Key Specifications

Pinout & Package

AD7828CQ is supplied in a 28-lead plastic dual-in-line package (PDIP, Q-28), 0.6" wide, compliant with JEDEC MS-011AB. Pin 1 identifier located at top-left corner when notch faces upward.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-channel, 8-bit ADC applications.

Compared with AD7828LN, AD7828CQ provides guaranteed performance over harsher thermal environments; compared with MAX195BCPP, AD7828CQ delivers integrated 8-channel acquisition with deterministic timing and lower system-level component count - critical for space-constrained, real-time embedded designs.

Availability

AD7828CQ is available at Aetrix Electronics and suitable for industrial data loggers, medical patient monitors, and automotive diagnostic scanners requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD7828CQ 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, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, founded in 1965 and headquartered in Wilmington, MA.

The AD7828CQ belongs to Analog Devices' legacy LC2MOS precision data acquisition product line, designed specifically for cost-sensitive, multichannel industrial and instrumentation applications where integration, reliability, and ease of microprocessor interfacing are prioritized over ultra-high resolution.

FAQ

What is the operating temperature range for the AD7828CQ?

The AD7828CQ is rated for industrial operation from –40°C to +85°C. This specification is confirmed in the Ordering Guide section of the AD7824/AD7828 Rev. F datasheet, where "C" grade denotes the –40°C to +85°C range and "Q" package indicates the 28-lead PDIP. The device maintains ±1/2 LSB total unadjusted error across this full range.

Does the AD7828CQ require an external clock signal to operate?

No, the AD7828CQ does not require an external clock. Its half-flash conversion architecture internally generates timing for both the 4-bit MSB and LSB flash stages. As stated in the General Description, "the half-flash conversion technique means that there is no need to generate a clock signal for the ADC," enabling simpler system timing and eliminating clock jitter sensitivity.

How is channel selection implemented on the AD7828CQ?

Channel selection on the AD7828CQ is performed using three address inputs: A0, A1, and A2. These pins decode eight combinations (000–111) to select AIN1 through AIN8, as defined in Table I of the datasheet. In Mode 0, addresses must remain stable while CS and RD are low; in Mode 1, the address is latched on the rising edge of RD.

What is the purpose of the RDY and INT outputs on the AD7828CQ?

RDY is an open-drain ready signal used in Mode 0 to drive a microprocessor's WAIT input - it goes low at CS fall and returns high-impedance when conversion completes. INT is an active-low interrupt that asserts at conversion completion and clears on rising CS or RD. RDY is unused and must be tied to GND in Mode 1, while INT remains functional for notification.

Can the AD7828CQ interface directly with a 3.3 V microcontroller?

The AD7828CQ digital inputs (CS, RD, A0–A2) accept TTL/CMOS logic levels with VINH ≥2.4 V and VINL ≤0.8 V, making them compatible with 3.3 V systems when driven actively. However, its DB0–DB7 outputs swing to 4.0 V min (VOH) under 360 µA load - level-shifting or pull-up to 3.3 V is required for reliable reception by 3.3 V-only inputs.