Texas Instruments LM1949N/NOPB

Overview

LM1949N/NOPB from Texas Instruments is a dedicated fuel injector drive controller IC designed to manage peak-and-hold current profiles for automotive solenoid actuators. It delivers 22 mA output drive current, supports 3V–5.5V supply operation, provides internally set 4× peak-to-hold current ratio, includes short-circuit protection, and operates across −55°C to +125°C ambient temperature - enabling robust cold-crank performance in engine control units.

For engineers reviewing the LM1949N/NOPB datasheet, LM1949N/NOPB pinout, LM1949N/NOPB application, or LM1949N/NOPB equivalent, this device is selected for precise solenoid timing control, low-RFI injector drive, TTL/CMOS-compatible input logic, externally adjustable holding current, and integrated timer-based timeout protection in safety-critical power actuation circuits.

Technical Context

The LM1949N/NOPB implements a dual-mode current control architecture: it first drives an external NPN Darlington transistor into saturation to deliver peak current (typically 4× IH), then transitions to closed-loop op-amp regulation to maintain precise hold current via sense-resistor feedback at Pin 4 (SENSE) and Pin 5 (GND). The internal peak threshold is fixed at ~386 mV, while hold reference is ~94 mV - both referenced to the sense resistor voltage drop.

Timing behavior is governed by an external RC network on Pin 8 (TIMER), with timeout triggered when capacitor voltage reaches ~63% of V_CC; grounding Pin 8 disables timing. Input logic on Pin 1 accepts TTL/CMOS levels, and compensation between Pins 2 (COMP) and 3 (OUT) stabilizes the error amplifier during hold-state regulation.

Key Specifications

Pinout & Package

LM1949N/NOPB is housed in an 8-pin plastic dual in-line package (PDIP), RoHS-compliant with NiPdAu lead finish, MSL Level-1 rating, and tube packaging (40 units per tube). Package dimensions: 502 mm × 14 mm × 11.938 mm (L × W × T), with 4.32 mm alignment groove width.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar injector drive controller applications.

Compared with LM1949N/NOPB, the L9369-TR offers higher integration and diagnostics but demands more complex layout and firmware coordination, while the ADUM7234BRZ shifts current control responsibility to the host processor and adds isolation overhead - neither replicates the LM1949N/NOPB's self-contained, analog peak-and-hold timing with zero-software overhead.

Availability

LM1949N/NOPB is available at Aetrix Electronics and suitable for automotive engine control units, fuel system modules, and industrial solenoid actuation systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LM1949N/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 automotive-grade ICs with broad portfolio coverage and long-term product longevity commitments.

The LM1949N/NOPB belongs to TI's automotive analog power interface product line, engineered specifically for robust, low-EMI solenoid and injector drive in engine management systems where reliability under extreme thermal and electrical stress is non-negotiable.

FAQ

What is the primary function of the LM1949N/NOPB in an automotive fuel system?

The LM1949N/NOPB serves as a dedicated analog injector drive controller that autonomously manages peak-and-hold current profiles for electromagnetic fuel injectors. It ensures rapid solenoid opening via high initial current (up to 4× hold level), then reduces to a lower sustaining current - all without microcontroller intervention. This function is central to the LM1949N/NOPB's role in improving fuel metering accuracy, reducing coil heating, and maintaining operation during low-battery cranking events.

Can the LM1949N/NOPB operate from a 3.3 V supply, and what are the implications?

Yes, the LM1949N/NOPB is fully specified for 3.0 V to 5.5 V operation, making it compatible with 3.3 V systems. At 3.3 V, input logic thresholds scale accordingly (e.g., VOL max = 1.15 V), and sense reference voltages remain accurate (VH = 94 mV typ). However, output drive strength decreases slightly - peak sink current drops to ~−18 mA - which may require verification with the selected Darlington transistor's base drive requirements in the LM1949N/NOPB application circuit.

How does the LM1949N/NOPB implement peak-and-hold current control without a microcontroller?

The LM1949N/NOPB uses internal analog comparators and a state machine to autonomously switch between modes: upon IN pin assertion, it forces OUT (Pin 3) to sink maximum current until SENSE (Pin 4) voltage reaches ~386 mV (peak threshold), then transitions to op-amp regulation to hold ~94 mV across the sense resistor. This entire sequence - including timing, threshold detection, and mode switching - is implemented in analog circuitry within the LM1949N/NOPB die, requiring no firmware or external timing logic.

What is the purpose of the TIMER pin (Pin 8) on the LM1949N/NOPB, and how is it configured?

The TIMER pin (Pin 8) on the LM1949N/NOPB sets a timeout period to force transition from peak to hold mode if the solenoid current fails to reach the peak threshold - critical during low-battery cranking. It is configured with an RC network where time constant τ = R_T × C_T; timeout occurs when capacitor voltage reaches ~63% of V_CC. Grounding Pin 8 disables timing, while leaving it open enables default operation. This behavior is intrinsic to the LM1949N/NOPB's internal timer circuit and requires no external clock or software control.

Is the LM1949N/NOPB pin-compatible with other injector drivers such as the LM1948 or UC2913?

No, the LM1949N/NOPB is not pin-compatible with LM1948 or UC2913. The LM1948 uses a different pinout (e.g., COMP and OUT swapped), and UC2913 is a current-mode PWM controller with distinct functional blocks (error amp, oscillator, PWM comparator) and incompatible signal routing. Substituting any of these requires PCB redesign and firmware adaptation - the LM1949N/NOPB's 8-pin PDIP layout and signal assignment are unique to its peak-and-hold architecture.