Analog Devices Inc. AD7870KNZ

Overview

AD7870KNZ from Analog Devices is a complete monolithic 12-bit LC2MOS sampling ADC with integrated track-and-hold amplifier (2 μs acquisition), laser-trimmed internal clock, on-chip 3 V buried Zener reference, and parallel/byte/serial digital interface. It supports ±3 V bipolar input range, achieves 70 dB SNR at 10 kHz, and delivers 57 ns data access time for microprocessor interfacing in data acquisition systems.

For engineers reviewing the AD7870KNZ datasheet, AD7870KNZ pinout, AD7870KNZ application, or AD7870KNZ equivalent, this page provides verified technical context, real-world interface timing constraints, confirmed dynamic and dc accuracy specs, package-specific pin mapping, and validated alternative options for industrial signal conditioning and DSP front-end designs.

Technical Context

The AD7870KNZ implements a successive approximation register (SAR) architecture with a voltage-output DAC and high-speed comparator. Its internal 3 V reference is laser-trimmed and temperature-compensated (±35 ppm/°C max for K-grade), directly biasing the bipolar input stage and DAC. Conversion is initiated asynchronously via CONVST rising edge or CS falling edge.

It supports three output formats: 12-bit parallel (DB11–DB0), two 8-bit bytes (with HBEN control), or serial (SDATA/SCLK/SSTRB with open-drain outputs requiring external pull-ups). Internal clock operation yields 6.5 μs min / 9 μs max conversion time; external 2.5 MHz clock guarantees ≤8 μs conversion.

Key Specifications

Pinout & Package

AD7870KNZ is supplied in a 24-pin, 0.3-inch-wide plastic DIP package (N-24). Pin functions are electrically identical across DIP and SOIC variants per Analog Devices Rev. C datasheet.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 12-bit sampling ADC applications.

Compared with AD7871KNZ, AD7870KNZ offers superior reference stability for precision DC measurements; compared with ADS7822U, AD7870KNZ provides flexible multi-format interfacing and true bipolar input capability essential for industrial transducer signal chains.

Availability

AD7870KNZ is available at Aetrix Electronics and suitable for industrial data acquisition, test equipment, motor control, and medical instrumentation requiring stable component supply across extended product lifecycles.

Supply support for AD7870KNZ 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, headquartered in Norwood, MA.

The AD7870KNZ belongs to the AD787x family of complete monolithic sampling ADCs designed specifically for high-accuracy, low-latency data acquisition in industrial and instrumentation systems requiring self-contained timing and reference.

FAQ

What is the maximum input frequency the AD7870KNZ can accurately digitize?

The AD7870KNZ track-and-hold amplifier acquires input signals to 12-bit accuracy in under 2 μs and supports full-power input frequencies up to 50 kHz. Its 0.1 dB bandwidth is typically 500 kHz, enabling faithful digitization of signals well above the Nyquist rate of its 100 kHz sampling capability. For optimal SNR, input signals should remain below 50 kHz to avoid aliasing and maintain specified 70 dB performance.

Does the AD7870KNZ require external components to operate?

No, the AD7870KNZ is a complete ADC requiring only power supply decoupling capacitors. It integrates a 3 V buried Zener reference, laser-trimmed clock oscillator, track-and-hold amplifier, and 12-bit SAR core. External pull-up resistors (4.7 kΩ on SSTRB/SDATA, 2 kΩ on SCLK) are needed only for serial interface operation - not for basic parallel-mode functionality.

How does the AD7870KNZ handle bipolar versus unipolar input ranges?

The AD7870KNZ is specifically configured for ±3 V bipolar input. Its internal 3 V reference biases the input stage for symmetric positive/negative signal handling, producing twos-complement output codes. This differs from the AD7875 (0 V to +5 V, straight binary) and AD7876 (±10 V, twos-complement). The AD7870KNZ cannot natively accept unipolar or ±10 V inputs without external scaling.

What is the purpose of the 12/8/CLK pin on the AD7870KNZ?

The 12/8/CLK pin configures both data format and serial clock behavior. At +5 V, it selects 12-bit parallel-only output. At 0 V, it enables byte or serial mode with gated SCLK (stops after transmission). At −5 V, it enables byte or serial mode with continuous SCLK. This single pin eliminates external mode-select logic, simplifying interface design across multiple host architectures.

Can the AD7870KNZ operate with an external clock, and what are the timing implications?

Yes, the AD7870KNZ accepts an external TTL-compatible clock on the CLK pin. With a 2.5 MHz external clock, conversion time is guaranteed ≤8 μs. Using the internal laser-trimmed oscillator yields 6.5 μs min / 9 μs max conversion time. External clocking allows synchronization to system timing domains but requires careful routing to minimize jitter, which directly impacts SNR performance.