Analog Devices Inc. DC951A

Overview

LTC2481 from Analog Devices (formerly Linear Technology) is a 16-bit + sign delta-sigma analog-to-digital converter with patented Easy Drive input current cancellation, I²C interface, and on-chip programmable gain (1–256). It digitizes rail-to-rail differential inputs with zero net differential input current, supports 50/60Hz simultaneous line rejection, and operates from 2.7V to 5.5V supply - enabling direct high-impedance sensor interfacing in precision weight scales and industrial process control.

For engineers reviewing the LTC2481 datasheet, LTC2481 pinout, LTC2481 application, or LTC2481 equivalent, key selection considerations include its no-latency digital filter settling in one cycle, ±2 ppm INL, 1 µV offset error, internal oscillator eliminating external crystals, and six I²C addresses for multi-device bus configurations.

Technical Context

The LTC2481 employs a third-order delta-sigma modulator with continuous auto-calibration of offset and full-scale, achieving no missing codes and transparent correction without interrupting conversion flow. Its Easy Drive sampling architecture cancels dynamic input current errors by balancing charge injection across IN+ and IN–, enabling accurate digitization even with source impedances >100 kΩ.

It integrates a programmable-gain amplifier (PGA), internal temperature sensor, and configurable digital notch filters for 50 Hz, 60 Hz, or simultaneous 50/60 Hz rejection. The device supports two speed modes: standard (157–160 ms conversion time) and 2× speed (79–82 ms), with corresponding trade-offs in noise (0.6 µV_RMS vs. 0.84 µV_RMS) and offset error (0.5 µV vs. 0.5 mV).

Key Specifications

Pinout & Package

Package: 10-lead (3 mm × 3 mm) plastic DFN with exposed pad (Pin 11 = GND, must be soldered to PCB).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS124S08 and MAX11200, the LTC2481 uniquely combines 16-bit precision with zero-net differential input current, autonomous line-frequency rejection, and six I²C addresses in a 3 mm × 3 mm DFN - making it optimal for compact, multi-sensor industrial nodes where input buffering and external clocking must be minimized.

Availability

LTC2481 is available at Aetrix Electronics and suitable for weight scales, industrial process controllers, direct temperature measurement systems, and strain gauge transducer interfaces requiring stable component supply across automotive, industrial, and medical OEM programs.

Supply support for LTC2481 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 technologies, serving industrial, automotive, communications, and healthcare markets.

The LTC2481 belongs to ADI's precision delta-sigma ADC product line, designed specifically for high-accuracy, low-power, direct-sensor-digitization applications where input buffering, external clocks, and complex calibration must be eliminated.

FAQ

What is the maximum source impedance the LTC2481 can drive without accuracy loss?

The LTC2481's Easy Drive technology cancels differential input current, allowing accurate digitization with source impedances up to 100 kΩ on both IN+ and IN–. This is confirmed by the "+FS Error vs RSOURCE" plot in the datasheet showing <20 ppm error at 100 kΩ. No external buffer is required - the LTC2481 itself maintains 16-bit linearity and <1 µV offset error under these conditions.

Does the LTC2481 require an external crystal or oscillator?

No - the LTC2481 includes an on-chip trimmed oscillator that eliminates the need for external timing components. It achieves ±0.1% frequency stability over temperature and supports all operating modes (50 Hz, 60 Hz, simultaneous 50/60 Hz) internally. An external oscillator (10–1000 kHz) may be used via the CA0/f0 pin for tighter line-frequency null placement, but is optional.

How many unique I²C addresses does the LTC2481 support?

The LTC2481 supports six unique I²C addresses via combinations of CA0/f0 and CA1 pin states (LOW/HIGH/FLOAT). CA0/f0 provides two states (HIGH or FLOAT), CA1 provides three (LOW/HIGH/FLOAT), yielding 2 × 3 = 6 distinct addresses. This enables up to six LTC2481 devices on a single I²C bus without address conflicts or external multiplexers.

What is the conversion time of the LTC2481 in 50 Hz rejection mode?

In standard (1×) speed mode with 50 Hz rejection enabled, the LTC2481 has a conversion time of 157.2 ms (typical) at 25°C. In 2× speed mode, this reduces to 78.7 ms. Both values are specified over the full temperature range for C/I-grade parts and include full auto-calibration cycles - no additional settling delay is required before reading the result.

Can the LTC2481 measure its own die temperature?

Yes - the LTC2481 integrates an on-chip PTAT (proportional-to-absolute-temperature) sensor with a nominal output of 420 mV at 27°C (390–450 mV range). This signal is selectable via the configuration register and digitized alongside analog inputs, enabling self-temperature monitoring without external components. Accuracy is ±2°C over –40°C to +125°C for H-grade parts.