Texas Instruments LM3813M-1.0/NOPB

Overview

LM3813M-1.0/NOPB from Texas Instruments is a precision low-side current gauge IC featuring an integrated 0.004Ω sense element, ±2% room-temperature accuracy, PWM output encoding current magnitude and direction, and 50 ms sampling interval. It operates from 2V to 5.25V and delivers 1A full-scale sensing for battery charge/discharge monitoring and smart fuse applications.

For engineers reviewing the LM3813M-1.0/NOPB datasheet, LM3813M-1.0/NOPB pinout, LM3813M-1.0/NOPB application, or LM3813M-1.0/NOPB equivalent, key selection criteria include low-side sensing topology, PWM interface compatibility with microcontrollers, thermal stability over −40°C to +125°C, and shutdown quiescent current of 2.5 µA.

Technical Context

The LM3813M-1.0/NOPB implements a delta-sigma analog-to-digital converter to digitize sensed current, followed by digital filtering and ramp-comparison logic to generate a duty-cycle-modulated PWM waveform. Current averaging occurs over fixed 50 ms intervals, rejecting sub-50 ms transients.

Its PWM output encodes bidirectional current: 50% duty cycle = zero current; >50% = positive flow; <50% = negative flow. The internal sense element's 2600 ppm/°C temperature coefficient is compensated in the signal path, enabling ±2% accuracy at 25°C and stable operation across industrial temperature range.

Key Specifications

Pinout & Package

LM3813M-1.0/NOPB uses an 8-pin SOIC (D0008A) package with exposed pad for thermal enhancement. Pin 1 serves as SENSE+ and GND reference; Pin 8 supplies VDD. Ground pins (7 and 1) are separated to isolate high-current sense return from digital ground.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA240A1QDRQ1 and ACS724LLCTR-10AU-T, LM3813M-1.0/NOPB uniquely combines ultra-low-loss integrated sensing, digital PWM output, and 50 ms averaging in a single 8-pin SOIC-reducing BOM count and firmware complexity for cost-sensitive, noise-prone battery and load management systems.

Availability

LM3813M-1.0/NOPB is available at Aetrix Electronics and suitable for battery management systems, motion control diagnostics, and resettable smart fuse designs requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LM3813M-1.0/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 delivering analog, embedded processing, and connectivity solutions with emphasis on reliability, energy efficiency, and system integration.

The LM381x family was designed specifically for precision, low-insertion-loss current measurement in battery-powered and industrial equipment-enabling accurate energy accounting without external shunts or complex signal conditioning.

FAQ

What is the sensing topology supported by LM3813M-1.0/NOPB?

The LM3813M-1.0/NOPB is configured exclusively for low-side current sensing. Pin 1 functions as both SENSE+ and GND reference, while Pin 2 is SENSE−, connecting to the load side of the current path. This topology avoids high-voltage common-mode challenges but requires the load to be grounded referenced. High-side sensing requires LM3812M-1.0/NOPB instead.

How does the PWM output of LM3813M-1.0/NOPB encode current magnitude and direction?

The LM3813M-1.0/NOPB PWM output uses duty cycle to represent signed current: 50% duty cycle equals 0 A; values above 50% indicate positive current (e.g., 95.5% = +1 A); values below 50% indicate negative current (e.g., 4.5% = −1 A). The relationship is linear per I_SENSE = 2.2 × (D − 0.5) × I_MAX, where D is measured duty cycle and I_MAX = 1 A for LM3813M-1.0/NOPB.

What is the role of the FLTR+ and FLTR− pins on LM3813M-1.0/NOPB?

FLTR+ and FLTR− form a differential anti-aliasing input to the delta-sigma modulator. A 0.1 µF ceramic capacitor must be placed between them to limit input bandwidth to ~10 Hz, preventing aliasing of high-frequency noise into the 20 Hz PWM output. This passive RC filter is essential for stable current measurement and is specified in TI's application circuits.

Can LM3813M-1.0/NOPB operate from a 3.3 V supply?

Yes, LM3813M-1.0/NOPB operates across 2.0 V to 5.25 V, making it fully compatible with standard 3.3 V logic systems. At 3.3 V, the PWM high-level output is guaranteed ≥3.1 V (VDD − 0.2 V) with 1 mA sink, ensuring robust interfacing to 3.3 V microcontrollers without level shifters. Quiescent current remains stable across this range.

What thermal considerations apply to LM3813M-1.0/NOPB accuracy?

LM3813M-1.0/NOPB achieves ±2% accuracy at 25°C, but thermal gradients between the internal sense element and die affect long-term stability. Layout best practices-such as using ≥100 mm² copper pour under pins 1 and 2-minimize thermal resistance and keep errors below ±3% over −40°C to +125°C. The datasheet specifies 2600 ppm/°C sense resistor TC, partially compensated in signal path.