Texas Instruments LM3813M-7.0/NOPB

Overview

LM3813M-7.0/NOPB from Texas Instruments is a precision low-side current gauge IC featuring an integrated 0.004Ω sense element, ±7A continuous sensing range, PWM output encoding current magnitude and direction, and 50 ms sampling interval. It delivers ±2% accuracy at room temperature and operates from 2V to 5.25V supply, enabling accurate battery discharge monitoring in portable power systems.

For engineers reviewing the LM3813M-7.0/NOPB datasheet, LM3813M-7.0/NOPB pinout, LM3813M-7.0/NOPB application, or LM3813M-7.0/NOPB equivalent, key selection considerations include low-side sensing topology, PWM interface compatibility with microcontrollers, thermal layout sensitivity for 7A accuracy, shutdown quiescent current (2.5 µA), and D0008A SOIC-8 package constraints.

Technical Context

The LM3813M-7.0/NOPB implements a delta-sigma analog-to-digital converter with internal anti-aliasing filtering via FLTR+/FLTR− pins, averaging current over fixed 50 ms intervals to reject transient spikes. Its PWM output encodes sensed current as duty cycle relative to 50% zero-current baseline, with 0.1% typical jitter and 1024-level quantization resolution.

Designed exclusively for low-side sensing, the device uses SENSE+ (tied to GND) and SENSE− as current path terminals, requiring careful PCB copper area design under these pins to maintain ±2% accuracy at 7A. The SD pin enables hardware-controlled entry into 2.5 µA shutdown mode, while VDD and GND are separated across pins 8 and 7 to support ground-referenced measurement integrity.

Key Specifications

Pinout & Package

LM3813M-7.0/NOPB is housed in an 8-pin SOIC package (D0008A), with exposed pad not electrically connected. Pin 1 serves dual function as SENSE+ and GND reference; pin 8 supplies VDD; pins 7 and 2 are dedicated GND and SENSE− respectively - critical for maintaining low-impedance ground return paths in high-current layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar current-sensing applications.

Compared with INA240A1QDRQ1 and ACS712ELCTR-05B-T, LM3813M-7.0/NOPB uniquely combines low-side topology, integrated 0.004Ω sensing, PWM output, and 50 ms averaging - making it optimal for cost-sensitive, low-power battery monitoring where isolation and high speed are unnecessary.

Availability

LM3813M-7.0/NOPB is available at Aetrix Electronics and suitable for battery charge/discharge gauge, motion control diagnostics, and resettable smart fuse applications requiring stable component supply, long-lifecycle support, and TI-qualified automotive-grade traceability.

Supply support for LM3813M-7.0/NOPB 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and digital signal technologies, with decades of expertise in precision sensing and power management ICs.

The LM381x family was designed specifically for high-accuracy, low-loss current measurement in portable and industrial power systems - prioritizing integration, thermal stability, and microcontroller-friendly digital output over analog flexibility or high-speed response.

FAQ

What is the sensing topology supported by LM3813M-7.0/NOPB?

The LM3813M-7.0/NOPB is designed exclusively for low-side current sensing, with SENSE+ (pin 1) tied to system ground and SENSE− (pin 2) placed between the load and ground return path. This configuration avoids high-voltage common-mode challenges but requires careful ground plane partitioning to prevent noise coupling. Unlike the LM3812 series, LM3813M-7.0/NOPB cannot be used for high-side sensing.

How does the PWM output of LM3813M-7.0/NOPB encode current magnitude and direction?

The LM3813M-7.0/NOPB PWM output uses a 50% duty cycle as the zero-current reference: duty cycles above 50% indicate positive current flow (e.g., 95.5% = +7 A), and below 50% indicate negative flow (e.g., 4.5% = −7 A). The relationship is linear per ISENSE = 2.2 × (D − 0.5) × IMAX, where D is measured duty cycle and IMAX = 7 A for LM3813M-7.0/NOPB. Quantization error of ±0.5 bit is inherent.

What is the accuracy specification for LM3813M-7.0/NOPB and under what conditions is it guaranteed?

LM3813M-7.0/NOPB guarantees ±2% average current accuracy at room temperature (25°C), tested at 2.5 A within the ±7 A range. This includes contributions from the internal sense element, delta-sigma conversion, and on-chip filtering. Accuracy degrades with temperature and depends critically on PCB copper area under pins 1 and 2 - poor thermal layout can increase error beyond ±2% at full scale.

Can LM3813M-7.0/NOPB be used in high-voltage applications exceeding 5.25 V?

Yes - while LM3813M-7.0/NOPB's VDD must remain within 2.0 V to 5.25 V, its low-side sensing architecture allows use in high-voltage systems (e.g., 24 V, 48 V) as long as the sense path remains ground-referenced and the IC's supply is locally regulated. Figure 21 in the datasheet shows a verified high-voltage low-side configuration using an LDO to derive VDD from the high-voltage rail.

What is the role of the FLTR+ and FLTR− pins on LM3813M-7.0/NOPB?

The FLTR+ and FLTR− pins on LM3813M-7.0/NOPB form the differential input to an internal anti-aliasing filter required for proper delta-sigma modulation. A 0.1 µF ceramic capacitor must be placed between them to set the filter cutoff frequency and prevent aliasing of high-frequency noise into the 50 ms averaged current measurement - omitting this capacitor causes significant accuracy degradation and false trip susceptibility.