Analog Devices Inc. AD7828LRSZ

Overview

AD7828LRSZ 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 data acquisition systems such as speech analysis and multichannel sensor monitoring.

For engineers reviewing the AD7828LRSZ datasheet, AD7828LRSZ pinout, AD7828LRSZ application, or AD7828LRSZ equivalent, this page delivers verified technical context, package-specific pin mapping, confirmed timing behavior under Mode 0/1, real-world interface examples (Z80, MC68000, TMS32010), and validated alternative options for industrial embedded designs requiring multichannel 8-bit sampling without external sample-and-hold circuitry.

Technical Context

The AD7828LRSZ employs a half-flash architecture: two 4-bit flash ADCs-one for MSBs and one for LSBs-combined with an internal 4-bit DAC to reconstruct and subtract the MSB analog approximation, enabling full 8-bit resolution without external clocking. Its analog input structure inherently performs sample-and-hold over ~1 µs, supporting 10 kHz full-scale sinusoidal inputs (157 mV/µs slew rate) on all eight channels.

Digital control uses Chip Select (CS) and Read (RD) signals only; address lines A0–A2 select among eight analog inputs (AIN1–AIN8). It operates in two modes: Mode 0 (WAIT-state microprocessors) uses RDY/INT for conversion synchronization, while Mode 1 (non-WAIT) reads prior result on first access and requires 2.5 µs inter-conversion delay. Both modes support direct ROM-style memory-mapped interfacing.

Key Specifications

Pinout & Package

AD7828LRSZ is packaged in a 28-lead SOIC (R-28) surface-mount package, 15.6 mm × 7.6 mm × 2.35 mm, with standard gull-wing leads and JEDEC MS-013AD compliance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7828LRSZ, AD7828LN offers identical performance in a through-hole package but lacks SMT compatibility, while MAX1138CPI+ trades parallel simplicity for serial flexibility and slightly slower conversion-making AD7828LRSZ optimal for µP-memory-mapped, low-latency, multichannel industrial acquisition.

Availability

AD7828LRSZ is available at Aetrix Electronics and suitable for industrial sensor monitoring, embedded data loggers, motor control feedback systems, and speech analysis equipment requiring stable component supply and long-term production continuity.

Supply support for AD7828LRSZ 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 AD7828LRSZ belongs to Analog Devices' legacy LC2MOS precision data acquisition product line, designed specifically for cost-sensitive, multichannel industrial and instrumentation applications where integration, low power, and microprocessor compatibility are critical.

FAQ

What is the maximum input signal frequency the AD7828LRSZ can accurately digitize without an external sample-and-hold?

The AD7828LRSZ supports full-scale sinusoidal inputs up to 10 kHz (157 mV/µs slew rate) across all eight channels without external sample-and-hold, thanks to its inherent track-and-hold architecture. This is confirmed in the datasheet's "INHERENT SAMPLE-HOLD" section and TPC 3 (SNR vs. Input Frequency), where SNR remains >40 dB up to 10 kHz at 400 kHz encode rate. The AD7828LRSZ achieves this by tracking the selected input for ~1 µs after conversion start, freezing the value used for LSB generation.

Does the AD7828LRSZ require an external clock signal to operate?

No, the AD7828LRSZ does not require an external clock signal. Its half-flash conversion architecture is fully controlled by the CS and RD digital inputs, as stated in the "GENERAL DESCRIPTION" and "TIMING AND CONTROL" sections. Timing diagrams (Figures 14 and 15) show all operations-including multiplexer selection, conversion initiation, and data validity-synchronized solely to CS/RD edges. This eliminates clock distribution complexity and associated jitter in µP-interfaced systems.

What are the key differences between Mode 0 and Mode 1 operation of the AD7828LRSZ?

Mode 0 requires microprocessor WAIT-state capability: a single CS+RD assertion starts conversion and holds the bus until RDY or INT signals data readiness. Mode 1 is WAIT-free: the first CS+RD reads the prior conversion result while starting a new one; the second CS+RD retrieves the new result. Mode 0 is used with Z80/MC68000; Mode 1 suits TMS32010. Both modes are electrically supported by the same AD7828LRSZ silicon-selection is purely firmware and system timing dependent.

Can the AD7828LRSZ perform bipolar input measurements?

Yes, the AD7828LRSZ supports bipolar operation via external signal conditioning. Figure 12 shows an AD544 op amp configured to shift and scale ±4 V inputs into the 0 V–5 V unipolar range accepted by AIN1–AIN8. With VREF (+) = 5 V and VREF (–) = 0 V, the resulting output uses complementary offset binary coding (Figure 13). The AD7828LRSZ itself is unipolar-only, but its fully differential reference inputs and flexible analog front-end enable robust bipolar measurement when paired with appropriate external circuitry.

What is the meaning of "LRSZ" in the part number AD7828LRSZ?

In AD7828LRSZ, "L" denotes ±1/2 LSB total unadjusted error grade, "R" indicates R-28 SOIC package (28-lead wide-body SOIC), "S" specifies commercial temperature range (0°C to +70°C), and "Z" signifies lead-free (RoHS-compliant) finish. This matches the Ordering Guide entry "AD7828LRS" (no Z) and Analog Devices' standard suffix conventions-confirmed by official AD7828 product pages and distributor listings (e.g., Digi-Key part #AD7828LRSZ-REEL).