Analog Devices Inc. LTC2945CUD-1#PBF

Overview

LTC2945CUD-1#PBF from Analog Devices is a rail-to-rail I²C power monitor IC that measures current (via ΔSENSE), input voltage (VIN), and calculates 24-bit power in real time. It operates from 2.7V to 80V supply, supports 0V–80V common-mode sensing, delivers ±0.75% total unadjusted error, and features split SDAI/SDAO pins for opto-isolated I²C - used in telecom power shelves and automotive battery monitoring.

For engineers reviewing the LTC2945CUD-1#PBF datasheet, LTC2945CUD-1#PBF pinout, LTC2945CUD-1#PBF application, or LTC2945CUD-1#PBF equivalent, key selection criteria include its inverted SDAO output for non-inverting opto-isolator compatibility, 12-lead 3mm × 3mm QFN package with exposed pad, 0°C to 70°C temperature grade, and support for continuous scan or snapshot ADC modes.

Technical Context

The LTC2945CUD-1#PBF integrates a 12-bit delta-sigma ADC with three independent measurement channels: differential shunt voltage (ΔSENSE, 102.4mV FS), supply voltage (VIN or SENSE+, 102.4V FS), and auxiliary external voltage (ADIN, 2.048V FS). Its onboard multiplier computes 24-bit power values digitally without host CPU intervention.

It implements programmable over/under-limit alerts with min/max tracking per channel, uses ADR0/ADR1 to select one of nine I²C addresses, and features dedicated SDAI (input) and inverted SDAO (output) pins - distinguishing it from the standard LTC2945 and enabling robust galvanic isolation in high-noise industrial bus systems.

Key Specifications

Pinout & Package

Package: 12-lead (3mm × 3mm) plastic QFN (UD package) with optional exposed pad (Pin 13) for thermal management. RoHS-compliant, lead-free finish (#PBF).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power monitoring applications.

Compared with LTC2945CUD#PBF, the LTC2945CUD-1#PBF's inverted SDAO simplifies opto-isolation hardware but shares identical accuracy, temperature range, and power architecture; versus INA226AIDGST, it trades resolution for autonomous 24-bit power calculation and 80V rail-to-rail capability.

Availability

LTC2945CUD-1#PBF is available at Aetrix Electronics and suitable for telecom infrastructure, automotive battery monitoring, and industrial PLC power telemetry requiring stable component supply and long-term lifecycle support.

Supply support for LTC2945CUD-1#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. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.

The LTC2945 product line delivers highly integrated, wide-input power monitoring solutions designed for reliability-critical systems where rail-to-rail sensing, autonomous power calculation, and robust I²C isolation are essential.

FAQ

What is the key functional difference between LTC2945CUD-1#PBF and LTC2945CUD#PBF?

The LTC2945CUD-1#PBF features an inverted SDAO (I²C data output) pin, enabling direct interface with inverting opto-couplers like the PC817 without external logic. The LTC2945CUD#PBF has a standard (non-inverted) SDAO. All other electrical specifications, pinout, package, and temperature rating are identical between the two variants.

Does LTC2945CUD-1#PBF support monitoring of negative supply rails such as –48V telecom systems?

Yes, the LTC2945CUD-1#PBF supports negative rail monitoring via low-side current sense topology. Its SENSE+ and SENSE– inputs accept 0V–80V common-mode voltage, allowing connection to the negative terminal of a –48V supply with proper grounding. Figure 4 in the datasheet confirms this configuration with GND referenced to the negative rail.

How does the onboard 24-bit power calculation in LTC2945CUD-1#PBF reduce firmware development effort?

The LTC2945CUD-1#PBF performs real-time multiplication of 12-bit current and voltage measurements internally, storing the full 24-bit result in dedicated I²C registers. This eliminates the need for host MCU to implement fixed-point arithmetic, handle overflow, or manage timing-critical sampling synchronization - reducing firmware validation scope and latency in power telemetry loops.

Can LTC2945CUD-1#PBF operate from a supply above 80V, and if so, how?

Yes, the LTC2945CUD-1#PBF can operate from supplies >80V using its INTVCC shunt regulator mode. Connect the high-voltage supply to INTVCC through an external shunt resistor sized per Equation 1 in the datasheet (e.g., 5.4kΩ for –48V telecom with 4mA load), limiting current to <35mA. The internal clamp regulates INTVCC to ~6.3V, powering the IC safely.

What is the purpose of the exposed pad (Pin 13) in the LTC2945CUD-1#PBF QFN package?

The exposed pad (Pin 13) in the LTC2945CUD-1#PBF's 12-lead QFN package is thermally conductive and electrically connected to GND internally. While optional, connecting it to a large PCB copper area significantly lowers θ_JA from 58.7°C/W to ~40°C/W, improving thermal margin during continuous operation at high VDD (e.g., 80V) and preventing junction temperature exceedance.