Diodes Incorporated AL5809-25S1-7

Overview

AL5809-25S1-7 from Diodes Incorporated is a two-terminal constant current linear LED driver in SOD-123 package, delivering 25mA ±5% regulated output over 2.5V–60V input-to-output voltage range and -40°C to +125°C ambient temperature. It supports both high-side and low-side LED string configurations, features 20ppm/°C temperature stability, and enables offline LED lamp designs without external current-setting resistors.

For engineers reviewing the AL5809-25S1-7 datasheet, AL5809-25S1-7 pinout, AL5809-25S1-7 application, or AL5809-25S1-7 equivalent, key selection criteria include its fixed 25mA output, SOD-123 thermal performance (θJA = 278.42°C/W), 60V IN-OUT rating for AC-coupled LED strings, and PWM dimming compatibility via external MOSFET switching at the OUT terminal.

Technical Context

The AL5809-25S1-7 integrates a low-dropout regulator powering an internal current regulation block with a factory-trimmed reference resistor and precision current mirror. Its floating-ground architecture allows bidirectional placement-IN connected to LED cathode (low-side) or OUT connected to LED anode (high-side)-with minimum startup voltage of 1.5V and thermal shutdown triggered at +165°C junction temperature.

It operates as a two-terminal series regulator: current flows unidirectionally from IN to OUT, with no ground reference required. The device exhibits <1% line regulation across 2.5V–60V V_IN-OUT, maintains ±5% current accuracy over full temperature range, and supports PWM dimming via external switch on the OUT pin with validated 500µs minimum on/off pulse widths.

Key Specifications

Pinout & Package

SOD-123 surface-mount package: compact 2.65mm × 1.55mm footprint, 0.3mm nominal height, single-row two-terminal configuration optimized for high-density LED board layouts and automated assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AL5809-25P1-7, the -25S1-7 trades thermal capability for space savings; compared with NSI45020T1G, it adds 60V rating, thermal protection, and superior temperature stability-making it the preferred choice for mains-connected or thermally demanding LED systems.

Availability

AL5809-25S1-7 is available at Aetrix Electronics and suitable for offline LED lamps, white goods illumination, instrumentation panel lighting, and LED power supplies requiring stable component supply, RoHS-compliant packaging, and long-lifecycle availability.

Supply support for AL5809-25S1-7 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 manufacturer of discrete semiconductors and analog ICs, specializing in high-reliability power management, signal integrity, and lighting solutions for industrial, automotive, and consumer markets.

The AL5809 product line delivers two-terminal constant current LED drivers optimized for cost-sensitive, space-constrained, and thermally challenging lighting applications-including retrofit lamps, appliance indicators, and signage-without external components.

FAQ

Can AL5809-25S1-7 be used in high-side configuration with the LED anode connected to IN?

No. In high-side configuration, the LED anode connects to the supply rail, the LED cathode connects to the OUT terminal, and the IN terminal connects to system ground or return path. The AL5809 conducts current from IN to OUT only; reversing polarity risks damage. Pin function is fixed: IN is always current input, OUT is always current output.

What is the maximum allowable power dissipation for AL5809-25S1-7 at 85°C ambient?

At 85°C ambient, the SOD-123 package's θ_JA = 278.42°C/W limits junction temperature rise to 70.5°C before reaching the +125°C max rating, allowing 0.253W max dissipation (70.5°C ÷ 278.42°C/W). With 25mA output, this corresponds to a maximum V_IN-OUT of 10.1V (0.253W ÷ 0.025A), verified in Figure 11 of the datasheet.

Does AL5809-25S1-7 require a heatsink for 25mA operation at 60V input-output differential?

Yes. At 60V × 25mA = 1.5W dissipation, the SOD-123 package exceeds its 0.36W rating by >4×. Even with aggressive copper pours and thermal vias, junction temperature would exceed +175°C. This condition is outside absolute maximum ratings and will cause immediate thermal shutdown or permanent damage. Use only within recommended V_IN-OUT limits shown in Figure 11.

How does PWM dimming interact with the AL5809-25S1-7's thermal shutdown feature?

PWM dimming reduces average power dissipation, lowering average junction temperature-but thermal shutdown responds to instantaneous junction temperature. During the ON pulse, full 25mA flows; if V_IN-OUT is high and duty cycle >50%, instantaneous power can still trigger shutdown. Designers must ensure peak pulse power stays below thermal limits using the t_{ON_MIN}/t_{OFF_MIN} constraints and derate V_IN-OUT accordingly.