Texas Instruments LM2793LDX

Overview

LM2793LDX from Texas Instruments (formerly National Semiconductor) is a low-noise, 1.5× CMOS charge pump LED driver IC with dual regulated constant-current outputs (up to 16 mA each), analog/PWM dual-function brightness control via SD-BRGT pin, and 500 kHz fixed-frequency operation - designed for white LED backlighting in portable Li-ion–powered devices such as cellular phones and PDAs.

For engineers reviewing the LM2793LDX datasheet, LM2793LDX pinout, LM2793LDX application, or LM2793LDX equivalent, key selection considerations include its 2.7V–5.5V input range, ±0.3% typical current matching between D1/D2 outputs, 3 µA shutdown current, LLP-10 package thermal performance, and dual-mode brightness control without external inductors.

Technical Context

The LM2793LDX implements a semi-regulated 1.5× switched-capacitor charge pump with pre-regulation to minimize input noise; POUT voltage is open-loop (1.5×VIN) below 3.3 V and loosely regulated to ~4.9 V above that threshold. Its dual current sources are internally mirrored from a reference set by SD-BRGT voltage or PWM duty cycle.

Soft-start limits inrush current during startup, and thermal protection disables operation above 150°C junction temperature. The device operates across –30°C to +100°C junction range with 55°C/W θJA in the LLP-10 package, requiring PCB thermal land and vias for optimal power dissipation management.

Key Specifications

Pinout & Package

LM2793LDX is housed in a 10-pin Leadless Leadframe Package (LLP-10), NS package number LDA10A, featuring an exposed die attach pad (2.0 mm × 1.2 mm) for thermal conduction to PCB copper.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar white LED constant-current driver applications.

Compared with TPS61160DRVR and MAX1910EUT+T, the LM2793LDX uniquely delivers matched dual-current outputs with analog+PWM dimming in an inductorless 3×3 mm package - making it optimal for compact, low-EMI dual-LED backlighting where board area and RF cleanliness are critical.

Availability

LM2793LDX is available at Aetrix Electronics and suitable for cellular phone backlighting, PDA display illumination, and handheld PC keypad lighting requiring stable component supply, long-term lifecycle support, and traceable sourcing for volume production.

Supply support for LM2793LDX 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 (TI) is a global semiconductor leader delivering analog, embedded processing, and connectivity solutions - acquired National Semiconductor in 2011 and maintains legacy product support including precision power management ICs.

The LM2793LDX belongs to TI's white LED driver product line, engineered specifically for low-noise, inductorless backlighting in battery-powered portable electronics where EMI, size, and dual-channel matching are design priorities.

FAQ

What is the function of the SD-BRGT pin on the LM2793LDX?

The SD-BRGT pin on the LM2793LDX serves a dual function: grounding it shuts down the device (reducing supply current to 3 µA), while applying 0.75–2.75 V sets LED current linearly from ~0.1 mA to 16 mA per channel. Voltages above 2.75 V enable full-scale output. It also accepts PWM signals (100 Hz–1 kHz) for digital brightness control. This integrated functionality eliminates need for separate enable and dimming pins in the LM2793LDX design.

Can the LM2793LDX drive a single LED at 32 mA by paralleling D1 and D2?

Yes - the LM2793LDX allows D1 and D2 outputs to be connected in parallel to drive one LED at up to 32 mA total current. To achieve this, configure SD-BRGT to set each channel to half the desired current (e.g., 15 mA per channel for 30 mA total). All electrical specifications - including headroom voltage, efficiency, and thermal limits - remain valid in this configuration, and no internal changes or derating is required for the LM2793LDX.

What capacitor types are recommended for use with the LM2793LDX?

The LM2793LDX requires four external ceramic capacitors: CIN, CHOLD, C1, and C2 - all rated at 1 µF with X7R or X5R dielectric. These offer low ESR (≤15 mΩ), stable capacitance over temperature, and minimal voltage coefficient. Y5V/Z5U ceramics are explicitly discouraged due to severe capacitance loss (down to 0.1 µF) under bias or temperature extremes, which risks failure to meet LM2793LDX's minimum capacitance requirements and causes regulation instability.

Does the LM2793LDX require an inductor in its application circuit?

No - the LM2793LDX uses a 1.5× CMOS charge pump architecture and operates entirely without an inductor. It relies solely on four external 1 µF ceramic capacitors (CIN, CHOLD, C1, C2) for energy transfer and regulation. This inductorless design reduces EMI, saves board space, lowers BOM cost, and simplifies layout - a defining feature of the LM2793LDX compared to boost-based LED drivers.

What is the thermal performance of the LM2793LDX in its LLP-10 package?

The LM2793LDX in LLP-10 package has a junction-to-ambient thermal resistance (θJA) of 55°C/W under standard JEDEC test conditions. With proper PCB layout - including a 1:1 thermal land under the exposed DAP and multiple thermal vias to inner ground planes - actual θJA can be reduced to ≤30°C/W. At 32 mA total load and 5.5 V input, calculated power dissipation is ~149 mW; with optimized layout, junction temperature stays well below the 100°C maximum operating limit even at 85°C ambient.