Analog Devices Inc. AD7870SQ

Overview

AD7870SQ from Analog Devices is a complete monolithic 12-bit successive approximation ADC with integrated track-and-hold amplifier (2 μs acquisition), on-chip 3 V buried Zener reference, laser-trimmed internal clock, and parallel/byte/serial digital interface. It operates from ±5 V supplies, accepts ±3 V analog input, achieves 70 dB SNR at 10 kHz, and delivers 57 ns data access time - enabling direct interfacing with 8-/16-bit microprocessors in data acquisition systems.

For engineers reviewing the AD7870SQ datasheet, AD7870SQ pinout, AD7870SQ application, or AD7870SQ equivalent, this page provides verified technical context, validated pin functions, confirmed dynamic and dc specifications, real-world application mappings, and two rigorously cross-checked alternative parts for signal chain design continuity.

Technical Context

The AD7870SQ implements a SAR architecture with a voltage-output DAC, high-speed comparator, and internal 3 V temperature-compensated Zener reference. Its track-and-hold transitions to hold mode on the rising edge of CONVST, supporting standalone or CS-triggered conversion initiation.

It supports three output formats: 12-bit parallel (DB11–DB0), two 8-bit bytes (via HBEN control), or serial (SDATA/SCLK/SSTRB), all synchronized to either its internal 2.5 MHz laser-trimmed clock or an external clock applied to CLK. Conversion time is 8 μs max with external clock or 6.5–9 μs with internal clock.

Key Specifications

Pinout & Package

AD7870SQ is supplied in a 24-pin, 0.3-inch-wide hermetic dual-in-line package (DIP), pin-compatible with industry-standard DIP-24 footprints. Pin functions are electrically validated 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 AD7871SQ, AD7870SQ offers commercial-temperature cost optimization without sacrificing functionality; versus MAX195BCPP, AD7870SQ delivers faster integration via self-contained clock and flexible interface - critical for rapid prototyping and legacy microprocessor compatibility.

Availability

AD7870SQ is available at Aetrix Electronics and suitable for industrial data acquisition, test equipment, medical instrumentation, and avionics signal conditioning requiring stable component supply across extended lifecycle programs.

Supply support for AD7870SQ 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, with decades of expertise in precision data conversion.

The AD7870SQ belongs to the LC2MOS 12-bit sampling ADC family designed specifically for embedded data acquisition systems demanding integration, low power, and guaranteed ac/dc performance without external support components.

FAQ

What is the maximum analog input frequency supported by the AD7870SQ?

The AD7870SQ supports full-power analog input signals up to 50 kHz while maintaining 12-bit accuracy. This is derived from its 100 kHz sampling rate and Nyquist criterion. The track-and-hold amplifier has a 0.1 dB bandwidth of ~500 kHz, ensuring minimal acquisition error even at high input frequencies. Verified dynamic specs (70 dB SNR, −80 dB THD) are guaranteed at 10 kHz input, with typical performance holding through 50 kHz per Analog Devices Rev. C datasheet.

Does the AD7870SQ require external components to operate?

No, the AD7870SQ is a complete monolithic ADC requiring only power supply decoupling capacitors. It integrates a 12-bit SAR core, 2 μs track-and-hold amplifier, laser-trimmed 2.5 MHz internal clock, and 3.00 V ±10 mV buried Zener reference. No external reference, clock crystal, or timing resistors are needed - confirmed in the "General Description" and "Product Highlights" sections of the official datasheet.

How does the AD7870SQ handle bipolar vs. unipolar input ranges?

The AD7870SQ is specifically configured for ±3 V bipolar input only. Its analog input structure uses twos complement coding with 1 LSB = 1.46 mV (FS = 6 V). Unlike the AD7875 (0 V to +5 V) or AD7876 (±10 V), the AD7870SQ's input scaling network and transfer function are fixed for ±3 V - confirmed in Figure 8, Table 1, and "Analog Input" section of the datasheet.

Can the AD7870SQ interface directly with an 8-bit microprocessor bus?

Yes, the AD7870SQ supports byte-mode interfacing via the HBEN pin and 12/8/CLK configuration. When 12/8/CLK is low and HBEN is asserted, DB7–DB0 deliver the lower byte and DB11–DB8 appear on DB3–DB0 - enabling seamless connection to 8-bit data buses without external latches. This is explicitly defined in Table 6 and "Two-Byte Read Interfacing" section.

What is the purpose of the 12/8/CLK pin on the AD7870SQ?

The 12/8/CLK pin configures both data format and serial clock behavior: at +5 V, only 12-bit parallel output is enabled; at 0 V, byte or serial mode activates with gated SCLK; at −5 V, byte or serial mode activates with continuous SCLK. This triple-function pin eliminates external mode-select logic - a key integration feature documented in Pin Function Descriptions and Figure 2.