Analog Devices Inc. LTC2421CMS#PBF

Overview

LTC2421CMS#PBF from Analog Devices (formerly Linear Technology) is a 1-channel, 20-bit micropower delta-sigma ADC in MSOP-10 package, operating from 2.7V to 5.5V supply. It delivers 8ppm INL, 1.2ppm RMS noise, and no-latency digital filtering that settles in a single conversion cycle. Designed for high-precision bridge digitization, it supports pseudo-differential inputs with extended range (–12.5% to +112.5% VREF) and integrated 50/60Hz notch rejection - ideal for strain gauge transducers and industrial weight scales.

For engineers reviewing the LTC2421CMS#PBF datasheet, LTC2421CMS#PBF pinout, LTC2421CMS#PBF application, or LTC2421CMS#PBF equivalent, key selection criteria include its 20-bit resolution with no missing codes, 200µA active supply current, internal oscillator eliminating external timing components, and compatibility with SPI/MICROWIRE interfaces in 3-wire mode.

Technical Context

The LTC2421CMS#PBF employs a proprietary delta-sigma architecture with a decimating FIR filter that achieves full settling in one conversion cycle - eliminating latency typical of conventional ∆Σ converters. Its digital filter nulls are programmable via the FO pin to target 50Hz (FO = GND), 60Hz (FO = VCC), or user-defined frequencies (1Hz–120Hz) using an external oscillator.

It features continuous auto-calibration of offset and full-scale every conversion, enabling exceptional stability over temperature, supply voltage, and time. Input range extends from ZSSET – 0.12·VREF to FSSET + 0.12·VREF (VREF = FSSET – ZSSET), supporting live-zero operation and seamless interfacing with sensor front-ends exhibiting offset/gain drift or overrange conditions.

Key Specifications

Pinout & Package

Package: 10-lead plastic MSOP (MS10), 3mm × 3mm, 0.5mm pitch, exposed pad (not electrically connected). Thermal resistance θJA = 130°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-resolution sigma-delta ADC applications.

Compared with ADS124S08IPW and LTC2401CMS#PBF, the LTC2421CMS#PBF uniquely combines 20-bit precision, integrated 110dB line-frequency rejection, 1.2ppm noise, and 20µA sleep current in a drop-in MSOP-10 footprint - making it optimal for battery-powered, EMI-prone, high-stability bridge sensing where simplicity and reliability are prioritized over raw bit count or speed.

Availability

LTC2421CMS#PBF is available at Aetrix Electronics and suitable for weight scales, direct temperature measurement, and strain gauge transducers requiring stable component supply, long-term calibration integrity, and robust 50/60Hz interference immunity.

Supply support for LTC2421CMS#PBF 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 LTC2421CMS#PBF belongs to ADI's precision delta-sigma ADC product line, designed specifically for low-power, high-accuracy sensor digitization in harsh electrical environments - emphasizing ease of use, self-calibration, and integrated anti-aliasing/noise rejection.

FAQ

What is the maximum sample rate of the LTC2421CMS#PBF?

The LTC2421CMS#PBF operates at a fixed conversion rate determined by its internal oscillator or external clock. With internal oscillator (FO = GND or VCC), conversion time is 131–163ms, yielding ~6–8 samples per second. When driven by an external oscillator, sample rate becomes f_EOSC/2560 - adjustable from ~0.4Hz to 47Hz. The LTC2421CMS#PBF does not support variable-rate oversampling or configurable data rates like SAR ADCs.

Does the LTC2421CMS#PBF require external passive components for basic operation?

No, the LTC2421CMS#PBF requires only two external bypass capacitors (10µF tantalum + 0.1µF ceramic on VCC-GND) for stable operation. Its internal oscillator eliminates crystals or RC networks; the extended input range removes need for external level-shifting or clamping circuits; and integrated calibration obviates trim pots or external reference buffers. No external timing, filtering, or gain-setting components are required for functional operation of the LTC2421CMS#PBF.

How does the LTC2421CMS#PBF handle input signals outside its nominal range?

The LTC2421CMS#PBF supports an extended input range of –12.5% to +112.5% VREF. Inputs within this range are converted linearly and accurately. Signals beyond this range are clamped: below –12.5% VREF output reads minimum code (00000H); above +112.5% VREF output reads maximum code (FFFFFH). Absolute maximum ratings (–0.3V to VCC+0.3V) still apply - exceeding them risks ESD diode conduction and increased leakage error. The LTC2421CMS#PBF thus safely manages sensor overrange and offset without external protection.

Is the LTC2421CMS#PBF compatible with standard SPI controllers?

Yes, the LTC2421CMS#PBF uses a 3-wire SPI-compatible interface (CS/SDO/SCK) with MSB-first, 24-bit frame format. It supports both internal clock mode (SCK output at 19.2kHz) and external clock mode (SCK input up to 2MHz). While not a full 4-wire SPI slave, its timing aligns with MICROWIRE and many microcontroller SPI peripherals in 3-wire master mode. No configuration registers or command sequences are needed - the LTC2421CMS#PBF begins conversion automatically upon power-up and responds to CS/SCK edges per documented timing diagrams.

What is the purpose of the FSSET and ZSSET pins on the LTC2421CMS#PBF?

FSSET and ZSSET define the full-scale and zero-scale reference points for the LTC2421CMS#PBF's pseudo-differential input. VREF = FSSET – ZSSET sets the effective reference voltage. When VIN = ZSSET, output = 00000H; when VIN = FSSET, output = FFFFFH. This allows ratiometric measurement against sensor excitation, accommodates sensor offset (e.g., live-zero RTDs), and enables flexible scaling without external op-amps. Both pins accept DC voltages from 0.1V to VCC, and their difference determines resolution and noise performance - the LTC2421CMS#PBF leverages this to achieve 20-bit accuracy with simple two-resistor reference networks.