Analog Devices Inc./Maxim Integrated DS2740BU+T&R

Overview

DS2740BU+T&R from Maxim Integrated (now Analog Devices) is a 13-bit bidirectional coulomb counter IC for battery fuel gauging, featuring 6.25μV/RSNS current resolution, ±51.2mV input dynamic range, 0.878s conversion time, and Dallas 1-Wire® interface with unique 64-bit address-used in portable medical devices, smart battery packs, and handheld instrumentation requiring precise charge tracking.

For engineers reviewing the DS2740BU+T&R datasheet, DS2740BU+T&R pinout, DS2740BU+T&R application, or DS2740BU+T&R equivalent, key selection criteria include 1-Wire bus compatibility, 13-bit vs. 15-bit resolution trade-offs, external sense resistor value impact on LSB (e.g., 625μA with 10mΩ), sleep-mode current (≤1.25μA), and OVD pin-controlled standard/overdrive timing selection.

Technical Context

The DS2740BU+T&R implements a differential 13-bit + sign ADC sampling IS1–IS2 at 18.6kHz to measure voltage drop across an external sense resistor (RSNS), with automatic offset correction occurring ~4× per hour. Its 1-Wire interface supports both standard (60–120μs slot) and overdrive (6–16μs slot) timing modes selected via the OVD pin.

Current accumulation occurs in a 16-bit register (ACR) with 6.25μVh/RSNS resolution and ±204.8mVh full-scale range, updated every 0.878s. The PIO pin functions as programmable open-drain I/O, configurable via Special Feature Register bit 6, and supports LED/vibrator drive or digital input sensing.

Key Specifications

Pinout & Package

DS2740BU+T&R is housed in an 8-pin μMAX package (3mm × 3mm, 0.8mm height), RoHS-compliant and tape-and-reel packaged for automated assembly.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar coulomb counter applications.

Compared with DS2740U+T&R, DS2740BU+T&R trades 2-bit resolution for 4× faster conversion and lower active current, making it optimal for duty-cycled portable gear. Versus BQ27426YZFT, DS2740BU+T&R offers simpler integration, no firmware dependency, and true 1-Wire multidrop capability-but lacks voltage-based SoC modeling.

Availability

DS2740BU+T&R is available at Aetrix Electronics and suitable for smart battery packs, portable medical devices, handheld test equipment, and industrial handheld scanners requiring stable component supply and long-term manufacturability.

Supply support for DS2740BU+T&R 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 acquired Maxim Integrated in 2021; Maxim was a leader in precision analog, mixed-signal, and battery-management ICs for industrial, medical, and portable applications.

The DS2740BU+T&R belongs to Maxim's legacy 1-Wire battery-monitoring product line, designed specifically for cost-sensitive, space-constrained systems needing standalone, high-accuracy coulomb counting without host processor overhead.

FAQ

What is the primary function of the DS2740BU+T&R?

The DS2740BU+T&R is a dedicated high-precision coulomb counter IC that measures bidirectional current flow across an external sense resistor and accumulates net charge in a 16-bit register. It delivers 13-bit resolution, 0.878s conversion time, and communicates via Dallas 1-Wire® interface-enabling accurate battery capacity monitoring in portable and industrial equipment without host-side integration complexity. The DS2740BU+T&R is optimized for low-power, single-wire, multi-device topologies.

How does the DS2740BU+T&R differ from the DS2740U+T&R variant?

The DS2740BU+T&R provides 13-bit + sign current resolution with 0.878s conversion time and 6.25μV/RSNS LSB, whereas the DS2740U+T&R offers 15-bit + sign resolution, 3.515s conversion time, and 1.56μV/RSNS LSB. Both share identical pinout, μMAX package, 1-Wire interface, and ACR resolution (6.25μVh/RSNS). The DS2740BU+T&R is selected when faster update rates and lower active power are prioritized over maximum current-measurement granularity.

Can the DS2740BU+T&R operate without an external sense resistor?

No-the DS2740BU+T&R requires an external current-sense resistor (RSNS) connected between SNS and VSS to convert load current into a measurable voltage. Typical values are 10mΩ or 20mΩ, which set the current-to-voltage scaling (e.g., 625μA LSB with 10mΩ). The IS1 and IS2 pins support optional RC filtering but do not replace the need for RSNS. Operation without RSNS results in undefined current measurement and invalid ACR accumulation.

What is the role of the OVD pin on the DS2740BU+T&R?

The OVD pin on the DS2740BU+T&R selects 1-Wire bus timing mode: logic high enables overdrive speed (6–16μs time slots), while logic low selects standard speed (60–120μs time slots). All devices on a multidrop 1-Wire bus must use the same OVD setting. The DS2740BU+T&R samples OVD at reset and maintains the selected mode until next power cycle or reset-ensuring deterministic communication timing without software configuration.

Does the DS2740BU+T&R support automatic offset calibration?

Yes-the DS2740BU+T&R performs automatic offset calibration approximately four times per hour by measuring its own input offset during dedicated conversion cycles. The resulting correction factor is applied to the next 1023 measurements. This process reduces systematic error to ≤±2 LSB (typical) without host intervention. Writing to the Accumulated Current Register (ACR) forces an immediate offset calibration, clearing fractional accumulation bits and restarting the measurement sequence.