Analog Devices Inc. AD7824LN

Overview

AD7824LN from Analog Devices is a 4-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 four multiplexed channels and is used in real-time data acquisition systems such as speech analysis and multichannel sensor monitoring.

For engineers reviewing the AD7824LN datasheet, AD7824LN pinout, AD7824LN application, or AD7824LN equivalent, key selection considerations include its half-flash architecture eliminating external clock requirements, 10 kHz full-scale signal handling per channel, microprocessor-compatible RD/CS interface, and N-24 DIP package compatibility with legacy industrial control boards.

Technical Context

The AD7824LN employs a half-flash conversion architecture using two 4-bit flash ADCs-one for MSBs and one for LSBs-with an internal 4-bit DAC reconstructing the MSB voltage for residual subtraction. This enables 2.5 µs conversion without external clock generation while maintaining 1/2 LSB accuracy over 0°C to 70°C.

It features a 4-channel analog multiplexer with A0/A1 address inputs, open-drain RDY and active-low INT outputs, three-state 8-bit parallel data bus (DB0–DB7), and fully differential reference inputs (VREF(+) and VREF(–)) supporting ratiometric and bipolar configurations via external op-amp conditioning.

Key Specifications

Pinout & Package

AD7824LN is packaged in a 24-lead plastic dual-in-line package (N-24), 0.3" wide, with 0.1" lead pitch and through-hole mounting. Pin 1 identifier located at top-left corner when viewed from top with notch facing up.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4-channel, 8-bit ADC applications.

Compared with AD7824KN, AD7824LN offers tighter accuracy for calibrated measurement systems; compared with MAX112, it provides integrated channel multiplexing and track-and-hold-reducing external component count and board space at the expense of resolution and interface flexibility.

Availability

AD7824LN is available at Aetrix Electronics and suitable for industrial sensor data loggers, embedded test equipment, speech analysis systems, and legacy control panel interfaces requiring stable component supply and long-term obsolescence management.

Supply support for AD7824LN 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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, communications, and automotive markets since 1965.

The AD7824LN belongs to Analog Devices' legacy LC2MOS precision data acquisition product line, designed specifically for cost-sensitive, microprocessor-based multichannel measurement systems requiring fast, self-contained ADC functionality without external clocking or sample-hold circuits.

FAQ

What is the maximum analog input frequency supported by the AD7824LN without external sample-and-hold?

The AD7824LN supports full-scale analog input frequencies up to 10 kHz without external sample-and-hold, enabled by its inherent track-and-hold function and 157 mV/µs slew rate capability. This is confirmed in the datasheet's "SINUSOIDAL INPUTS" section and verified by TPC 3 (Signal-to-Noise Ratio vs. Input Frequency), where SNR remains >40 dB up to 10 kHz at 400 kHz encode rate. The AD7824LN achieves this via simultaneous sampling of the selected channel for ~1 µs after conversion start.

Does the AD7824LN require an external clock signal to operate?

No, the AD7824LN does not require an external clock signal. Its half-flash conversion architecture uses two internal 4-bit flash ADCs and an integrated 4-bit DAC to generate the 8-bit result autonomously. 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", and the timing diagrams (Figures 14 and 15) confirm all timing is controlled solely by CS and RD edges.

What package type is used for the AD7824LN and is it RoHS-compliant?

The AD7824LN is supplied in a 24-lead plastic dual-in-line package (N-24), 0.3" wide, with through-hole leads. Per Analog Devices' historical product documentation and ordering guide, the N-24 variant predates RoHS compliance mandates and is not RoHS-compliant; leaded solder assembly is required. For RoHS-compliant alternatives, consult current-generation equivalents such as the AD7091R family, though these differ in architecture and pinout.

Can the AD7824LN perform bipolar input measurements?

Yes, the AD7824LN supports bipolar operation via external signal conditioning. Its fully differential reference inputs (VREF(+) and VREF(–)) allow offsetting the input range-for example, using an AD544 op-amp circuit (Figure 12) to map ±4 V input to 0 V–5 V at AIN1. The resulting output uses complementary offset binary coding, and the datasheet confirms LSB = 31.25 mV and full-scale = 8 V in this configuration, validated in Figure 13's transfer characteristic.

How does the AD7824LN handle channel selection and conversion initiation?

The AD7824LN selects analog channels using address inputs A0 and A1 (00 = AIN1, 01 = AIN2, 10 = AIN3, 11 = AIN4). Conversion initiates on the falling edge of both CS and RD in Mode 0, with RDY going low during conversion and returning high-impedance when data is ready on DB0–DB7. In Mode 1, RD latches the address on its rising edge and reads prior conversion data, requiring two consecutive RD cycles for new results-details are specified in Table I and Figures 14–15.