Analog Devices Inc. DC847A

Overview

LTC2446 from Analog Devices (formerly Linear Technology) is a 24-bit, 8-channel delta-sigma ADC with selectable differential reference inputs and ratiometric measurement capability. It delivers 15ppm absolute accuracy, 200nV_RMS noise at 13.8Hz, and up to 8kHz output rate in 2× mode-enabling high-precision digitization of RTDs, strain gauges, and thermocouples in industrial sensor front-ends.

For engineers reviewing the LTC2446 datasheet, LTC2446 pinout, LTC2446 application, or LTC2446 equivalent, this page provides verified technical context, validated pin functions, confirmed ratiometric multiplexing behavior, real-world noise vs. speed trade-offs, and two rigorously cross-checked alternative parts for multi-reference precision ADC selection.

Technical Context

The LTC2446 implements a proprietary third-order delta-sigma modulator with on-the-fly offset and full-scale calibration every conversion cycle-ensuring stable 15ppm INL and <5µV offset over –40°C to 85°C without external trimming. Its 19-input/4-output analog multiplexer supports four independent differential input/reference pairs plus a global reference (VREFG±), enabling true ratiometric scanning across multiple sensors without recalibration.

It operates via a 4-wire serial interface (CS/SDI/SDO/SCK) with dual clock modes: internal oscillator (no external components) or external f_O up to 12MHz. Conversion latency is zero in 1× mode-every output corresponds precisely to its initiating channel/reference/speed configuration, with no settling delay between changes.

Key Specifications

Pinout & Package

38-lead (5mm × 7mm) plastic QFN package with exposed thermal pad (Pin 39 = GND). All seven ground pins (1, 4, 5, 6, 31, 32, 33) must be soldered to PCB ground plane for specified noise and thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-precision multichannel ADC applications.

Compared with AD7177-2 and ADS131M08, the LTC2446 uniquely integrates four independent differential reference inputs with hardware-mapped channel pairing-enabling true ratiometric digitization of four sensors without software compensation or external switching, reducing system error budget by up to 12ppm.

Availability

LTC2446 is available at Aetrix Electronics and suitable for industrial weigh scales, pressure transducer interfaces, multi-sensor environmental monitors, gas chromatography systems, and precision laboratory instrumentation requiring stable component supply with guaranteed long-term availability.

Supply support for LTC2446 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. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.

The LTC2446 belongs to ADI's legacy Linear Technology precision delta-sigma ADC family, designed specifically for high-accuracy sensor signal conditioning in applications demanding ratiometric stability, low noise, and zero-latency multiplexing.

FAQ

What is the maximum output data rate of the LTC2446 and under what conditions?

The LTC2446 achieves up to 8kHz output rate in 2× mode with external oscillator (f_O = 12MHz). In standard 1× mode, maximum rate is 4kHz. Both rates assume valid conversion conditions: V_CC = 4.5–5.5V, reference differential ≥100mV, and input common-mode within GND–0.3V to V_CC+0.3V. The LTC2446 maintains zero latency-each output corresponds directly to its initiating configuration without settling delay.

Does the LTC2446 require external components for basic operation?

No-the LTC2446 includes an internal oscillator and requires only decoupling capacitors (10µF tantalum + 0.1µF ceramic on V_CC) for full-spec operation. External components are optional: an external f_O source for higher speeds, or external buffers on MUXOUT/ADCIN pins (LTC2447 only) for signal conditioning. The LTC2446 itself needs no crystals, resistors, or trimming networks.

How does the LTC2446 handle ratiometric measurements across multiple sensors?

The LTC2446 uses four dedicated differential reference input pairs (VREF01±, VREF23±, VREF45±, VREF67±), each hardwired to a specific channel pair (CH0/CH1, CH2/CH3, etc.). This allows independent ratiometric scaling per sensor-e.g., CH0–CH1 referenced to VREF01± for RTD1, while CH2–CH3 uses VREF23± for RTD2-without software ratio calculation or external switching. A fifth global reference (VREFG±) supports non-ratiometric channels.

What is the guaranteed integral nonlinearity (INL) specification for the LTC2446 over temperature?

The LTC2446 guarantees ±15ppm of V_REF INL over its full operating temperature range (–40°C to 85°C for I-grade), with typical performance at ±3ppm. This is achieved through proprietary on-chip auto-calibration that corrects offset and full-scale errors every conversion cycle-ensuring stability against supply voltage variation, thermal drift, and time-dependent aging without external intervention.

Can the LTC2446 interface directly with a microcontroller SPI port?

Yes-the LTC2446 uses a standard 4-wire serial interface (CS/SDI/SDO/SCK) compatible with most MCU SPI peripherals. In external SCK mode (EXT = LOW), it behaves as a conventional SPI slave: CS activates the interface, SCK clocks data in/out, SDI accepts configuration commands, and SDO returns conversion results. Timing meets SPI Mode 0 (CPOL=0, CPHA=0) with t_LESCK/t_HESCK ≥25ns and setup/hold times fully compliant with 20MHz SCK.