Diodes Incorporated AL8400QSE-7

Overview

AL8400QSE-7 from Diodes Incorporated is an automotive-grade linear LED driver-controller IC with open-collector output, 200mV precision current-sense reference voltage (V_FB), -40°C to +125°C operating range, and AEC-Q100 Grade 1 qualification. It regulates LED current via external MOSFET or NPN transistor in medium-to-high-current applications such as instrument cluster backlighting and LED signage.

For engineers reviewing the AL8400QSE-7 datasheet, AL8400QSE-7 pinout, AL8400QSE-7 application, or AL8400QSE-7 equivalent, key selection criteria include its 0.2V feedback threshold, 0.2–18V output swing capability, ±3% V_FB tolerance at 25°C, high PSRR (>45dB at 300kHz), and SOT353 thermal performance (θ_JA = 400°C/W).

Technical Context

The AL8400QSE-7 implements a transconductance error amplifier with 4500 mA/V gain and 600 kHz unity-gain bandwidth to regulate LED current via external R_SET. Its low 200mV V_FB minimizes I²R loss across the sense resistor, enabling efficient operation at currents up to 15 mA output sink capability.

It features an open-collector OUT pin compatible with both N-channel MOSFETs (e.g., DMN6068SE) and NPN transistors (e.g., DNLS320E), supporting flexible pass-element selection. The device maintains stability with external compensation (C_L ≥ 2 ms / R_B) and requires decoupling (C_D ≥ 0.1 µF X7R ceramic) placed within 5 mm of VCC and GND pins.

Key Specifications

Pinout & Package

SOT353 package: 5-pin, low-profile, RoHS-compliant, halogen- and antimony-free "Green" molding compound; 3000 units per 7″ tape and reel.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar linear LED driver-controller applications.

Compared with AL8400QSE-7, AL8862QSP-13 delivers higher efficiency in high-power LED arrays but adds EMI filtering complexity, while LM3407MMX/NOPB offers broader voltage flexibility without automotive validation-making AL8400QSE-7 optimal for thermally constrained, AEC-Q100–mandated linear LED regulation.

Availability

AL8400QSE-7 is available at Aetrix Electronics and suitable for automotive instrumentation, exterior signage, isolated offline LED lamps, and industrial panel illumination requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for AL8400QSE-7 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

Diodes Incorporated is a global semiconductor manufacturer specializing in discrete, analog, and mixed-signal solutions for automotive, industrial, and consumer markets.

The AL8400Q product line targets automotive-qualified linear LED control, emphasizing thermal robustness, low-loss current sensing, and compatibility with external high-voltage pass elements for flexible system architecture.

FAQ

What is the minimum recommended R_B value for stable operation with an NPN pass transistor?

The minimum R_B is determined by worst-case conditions: maximum V_CC, minimum V_BE, and maximum I_OUT. For AL8400QSE-7, with V_CC(max) = 12.6 V, V_BE(min) ≈ 0.4 V at +85°C, and I_OUT(max) = 15 mA, R_B(min) ≈ 480 Ω. Values below this risk exceeding the OUT pin's current rating and causing instability.

Can AL8400QSE-7 drive LED strings exceeding 18 V?

Yes - the AL8400QSE-7 itself operates up to 18 V on VCC, but its open-collector OUT pin controls an external pass device whose drain/collector connects to the full LED string voltage. VCC can be derived from the LED chain using a resistive divider and zener clamp (Figure 10) or tapped directly (Figure 11), enabling support for strings >60 V with appropriate external components.

How does the 200 mV V_FB improve thermal performance compared to 1 V references?

At 200 mV, power dissipated in R_SET is (0.2)²/R_SET, versus (1.0)²/R_SET for a 1 V reference - a 25× reduction. For a 150 mA LED current, R_SET = 1.33 Ω yields only 6 mW loss vs. 150 mW with 1 V, significantly lowering board temperature rise and easing thermal design in confined spaces.

Is CL mandatory, and what happens if it is omitted?

Yes - CL is mandatory for loop stability. Without it, the current control loop exhibits ~5 MHz oscillation due to phase shift from PCB trace inductance and OUT pin capacitance. The datasheet specifies CL × R_B ≥ 2 ms (e.g., 2.2 µF with 1 kΩ R_B); omitting CL causes visible LED flicker, audible noise, and potential pass-device overheating under load.