Texas Instruments LM3813MX-1.0

Overview

LM3813MX-1.0 from Texas Instruments is a precision low-side current gauge IC featuring an integrated 0.004Ω sense element, ±2% room-temperature accuracy (−1A to +1A range), PWM output encoding current magnitude and direction, and 50 ms sampling interval. It operates from 2V–5.25V supply and delivers <160 µA quiescent current in active mode-ideal for battery charge/discharge monitoring and smart fuse applications requiring zero external shunt.

For engineers reviewing the LM3813MX-1.0 datasheet, LM3813MX-1.0 pinout, LM3813MX-1.0 application, or LM3813MX-1.0 equivalent, key selection criteria include its factory-set ±1A sensing range, low-side topology compatibility with ground-referenced loads, PWM interface simplicity for microcontroller integration, and thermal stability over −40°C to +125°C junction temperature.

Technical Context

The LM3813MX-1.0 implements a delta-sigma analog-to-digital converter with internal anti-aliasing filtering (via FLTR+/FLTR− pins) to digitize sensed current, followed by digital averaging over 50 ms intervals. Its PWM output encodes current as duty cycle relative to 50% (zero current), with 0.1% typical jitter and 1024-level quantization resolution.

Designed exclusively for low-side sensing, the device integrates SENSE+ (tied to GND) and SENSE− terminals on pins 1 and 2, eliminating external shunts while maintaining ultra-low insertion loss. Shutdown control (pin 5) reduces quiescent current to 2.5 µA, and internal power-on reset ensures reliable initialization.

Key Specifications

Pinout & Package

LM3813MX-1.0 is housed in an 8-pin SOIC (D0008A) package with exposed pad for thermal enhancement. Pin 1 is SENSE+, internally connected to GND for low-side configuration; pin 8 is VDD. Ground connections occupy pins 7 and 8 (VDD) is separate.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM3813MX-1.0, the INA219BIDR offers higher resolution and digital interface flexibility but adds shunt design complexity and lacks native PWM direction encoding; the ACS712ELCTR-05B-T provides isolation at the cost of reduced accuracy, no averaging, and fixed 5V supply dependency.

Availability

LM3813MX-1.0 is available at Aetrix Electronics and suitable for battery management systems, motion control diagnostics, and power supply load monitoring requiring stable component supply and long-term lifecycle support.

Supply support for LM3813MX-1.0 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, precision, and energy efficiency.

The LM381x series was developed specifically for high-accuracy, low-loss current sensing in battery-powered and industrial systems where shunt-free operation and PWM interface simplicity are critical design requirements.

FAQ

What is the sensing topology supported by LM3813MX-1.0?

The LM3813MX-1.0 is designed exclusively for low-side current sensing. Its pin 1 (SENSE+) is internally tied to GND, and current flows from the load into pin 2 (SENSE−), through the internal 0.004Ω sense element, and out to system ground. This configuration avoids high-voltage common-mode challenges but requires the load to be referenced to ground - a key distinction from the high-side LM3812MX-1.0 variant.

How does the PWM output of LM3813MX-1.0 encode current magnitude and direction?

The LM3813MX-1.0 generates a PWM waveform where 50% duty cycle represents zero current. Duty cycles above 50% indicate positive current flow (e.g., 95.5% = +1.0 A), and below 50% indicate negative flow (e.g., 4.5% = −1.0 A). The relationship is linear: I_SENSE = 2.2 × (D − 0.5) × I_MAX, with D as measured duty cycle and I_MAX = 1.0 A for LM3813MX-1.0.

What is the role of the FLTR+ and FLTR− pins on LM3813MX-1.0?

FLTR+ and FLTR− form the differential input to the internal anti-aliasing filter for the delta-sigma modulator. A 0.1 µF ceramic capacitor must be placed between these pins to set the filter cutoff frequency and prevent aliasing of high-frequency noise into the 50 ms averaged current measurement. Omitting this capacitor degrades accuracy and increases susceptibility to EMI.

Can LM3813MX-1.0 operate from a 3.3V supply?

Yes, LM3813MX-1.0 supports supply voltages from 2.0 V to 5.25 V, making it fully compatible with standard 3.3V logic systems. At 3.3V, the PWM output maintains valid logic levels: VOH ≥ 3.1 V (with 1 mA sink) and VOL ≤ 0.2 V, ensuring reliable interfacing with 3.3V microcontrollers without level shifting.

What thermal considerations apply to LM3813MX-1.0 in continuous 1A operation?

At 1A continuous current, LM3813MX-1.0 dissipates ~4 mW (I²R = 1² × 0.004 Ω) - negligible self-heating. However, the internal sense resistor has a 2600 ppm/°C temperature coefficient, so board-level thermal design (e.g., copper pour under pins 1/2) is recommended to minimize die-to-sense-element thermal gradients that could affect long-term accuracy beyond the specified ±2%.