Analog Devices Inc. LT2940IDD#PBF

Overview

LT2940IDD#PBF from Analog Devices (acquired Linear Technology) is a high-side bidirectional power and current monitor IC featuring a four-quadrant analog multiplier, push-pull current-mode outputs for instantaneous power (PMON) and sensed current (IMON), ±5% power measurement accuracy, 4V–80V high-side sense range, and integrated comparator with latch control. It enables real-time forward/reverse power flow detection in industrial power supplies and server line cards.

For engineers reviewing the LT2940IDD#PBF datasheet, LT2940IDD#PBF pinout, LT2940IDD#PBF application, or LT2940IDD#PBF equivalent, key selection considerations include guaranteed ±0.4 V² full-scale power product accuracy, ±200 μA current-mode output compliance, –40°C to +85°C operating range, and DFN-12 (3 mm × 3 mm) thermal performance with exposed pad grounding.

Technical Context

The LT2940IDD#PBF implements a true four-quadrant analog multiplier core (K_PMON = 500 μA/V²) that computes instantaneous power as V_V × V_I, where V_V = V₊ – V_– (±8 V max differential) and V_I = I₊ – I_– (±200 mV max differential). Its push-pull PMON and IMON outputs source/sink ±200 μA with >500 kHz bandwidth, enabling direct RC filtering without op-amps.

Integrated comparator circuitry features 1.24 V reference with 35 mV hysteresis, dual open-collector outputs (CMPOUT/CMPOUT), and three-state LATCH pin control for latching or transparent mode operation. The device operates from 6 V to 80 V supply (100 V absolute max), with independent 4 V–80 V current-sense input voltage range decoupled from V_CC.

Key Specifications

Pinout & Package

LT2940IDD#PBF is housed in a 12-lead plastic DFN package (3 mm × 3 mm) with exposed thermal pad (Pin 13), rated for θ_JA = 43°C/W. The exposed pad may be left floating or connected to PCB ground for optimal thermal performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA226AIDGST and MAX4008AEUB+, the LT2940IDD#PBF uniquely integrates analog four-quadrant multiplication, dual current-mode outputs, and hardware comparator logic in one DFN package - eliminating ADC latency, firmware dependencies, and external signal conditioning for real-time power protection.

Availability

LT2940IDD#PBF is available at Aetrix Electronics and suitable for industrial power supplies, server line cards, and battery charger metering requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LT2940IDD#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, formed through acquisition of Linear Technology in 2017.

The LT2940 series was developed by Linear Technology specifically for high-accuracy, high-voltage, high-bandwidth analog power monitoring in industrial and telecom infrastructure - emphasizing simplicity, reliability, and hardware-level responsiveness over digital complexity.

FAQ

What is the guaranteed accuracy range for power measurement on the LT2940IDD#PBF?

The LT2940IDD#PBF guarantees ±5% full-scale power measurement accuracy when the product of voltage sense (V_V) and current sense (V_I) inputs remains within ±0.4 V², with V_V ≤ ±8 V and V_I ≤ ±200 mV. This region corresponds to quadrants I and III in Figure 4 of the datasheet. Outside this range, accuracy degrades as specified in the Electrical Characteristics table under "Quadrants I and III of Shaded Region".

Can the LT2940IDD#PBF monitor reverse power flow, and how is it indicated?

Yes, the LT2940IDD#PBF supports true bidirectional power monitoring via its four-quadrant multiplier architecture. Reverse power flow (e.g., regenerative braking) produces negative PMON output current (sinking mode), while forward power yields positive PMON current (sourcing mode). Polarity is preserved across the full ±200 μA output range, enabling direct determination of power direction without additional circuitry.

How does the LATCH pin function on the LT2940IDD#PBF, and what are its valid logic states?

The LATCH pin on the LT2940IDD#PBF controls comparator behavior in three states: open (high-impedance) enables transparent operation with hysteresis; voltage >2.5 V latches CMPOUT/CMPOUT upon CMP+ threshold crossing; voltage <0.5 V forces both comparator outputs low (clear state). The pin tolerates ±10 μA leakage and accepts voltages up to 100 V, making it robust against noise and compatible with direct connection to microcontroller GPIO or external logic.

What is the maximum allowable voltage on the I+ and I– pins of the LT2940IDD#PBF relative to ground?

The I+ and I– pins of the LT2940IDD#PBF each tolerate voltages from 4 V to 80 V above ground, independent of the V_CC supply voltage. Their differential input range is ±200 mV, with absolute maximum ratings of ±36 V differential and 100 V absolute on either pin. Exceeding 80 V violates the specified operating range and risks accuracy degradation or damage.

Does the LT2940IDD#PBF require external passive components for basic operation, and if so, which ones?

Yes - the LT2940IDD#PBF requires external components for full functionality: (1) a sense resistor between I+ and I– to convert load current to differential voltage; (2) resistive divider on V+/V– to scale bus voltage into ±8 V range; (3) load resistors on PMON and IMON (e.g., 10 kΩ) to convert current outputs to measurable voltages; (4) pull-up resistors on CMPOUT/CMPOUT (e.g., 10 kΩ to 3.3 V/5 V); and (5) 0.1 μF bypass capacitor on V_CC to GND. No external op-amps or ADCs are needed.