Diodes Incorporated AL5809-40S1-7

Overview

AL5809-40S1-7 from Diodes Incorporated is a two-terminal constant current linear LED driver in SOD-123 package, delivering 40mA ±5% regulated output over -40°C to +125°C ambient, with 2.5V–60V input-to-output voltage range and 20ppm/°C temperature drift. It supports both high-side and low-side LED string configurations for offline LED lamps and instrumentation illumination.

For engineers reviewing the AL5809-40S1-7 datasheet, AL5809-40S1-7 pinout, AL5809-40S1-7 application, or AL5809-40S1-7 equivalent, key selection criteria include its fixed 40mA current setting, SOD-123 thermal limits (0.36W max at TA=25°C), dual-side driving capability, and absence of external current-setting components.

Technical Context

The AL5809-40S1-7 integrates an internal precision current mirror and low-dropout regulator to maintain stable 40mA output across 2.5V–60V V_IN-OUT, with thermal shutdown triggered at +165°C junction temperature and 30°C hysteresis. Its floating ground architecture enables direct series connection with LED strings without reference to system ground.

It operates as a two-terminal current source: IN serves as current input (LED cathode for low-side, LED anode for high-side), OUT as current output (LED anode for low-side, LED cathode for high-side). Minimum on/off pulse widths are each 500µs, supporting PWM dimming between 100Hz–200Hz with duty cycle range 5–95%.

Key Specifications

Pinout & Package

SOD-123 surface-mount package with 2.55mm × 1.40mm body, 0.30mm lead length, and recommended 0.90mm × 4.05mm pad layout per Diodes Inc. AN-02007.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AL5809-40P1-7, the -40S1-7 trades thermal capacity for smaller footprint; versus NSI45020AZT1G, it adds 60V rating, thermal shutdown, and 40mA drive-enabling broader use in mains-connected and thermally demanding systems.

Availability

AL5809-40S1-7 is available at Aetrix Electronics and suitable for offline LED lamps, white goods illumination, and instrumentation panel lighting requiring stable component supply, RoHS-compliant packaging, and extended temperature operation.

Supply support for AL5809-40S1-7 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 company specializing in discrete, analog, and mixed-signal ICs, with emphasis on power management, signal integrity, and LED solutions.

The AL5809 belongs to Diodes' constant-current LED driver product line, designed specifically for cost-effective, resistorless linear LED regulation in AC/DC and DC/DC lighting systems where simplicity, reliability, and thermal robustness are prioritized.

FAQ

What is the maximum LED string voltage supported by AL5809-40S1-7?

The AL5809-40S1-7 supports up to 60V across its IN and OUT terminals. The maximum LED string voltage equals the supply voltage minus the minimum 2.5V headroom required for regulation. For example, with a 60V supply, the LED chain may be up to 57.5V (e.g., 18× 3.2V white LEDs). Thermal derating must be applied above 25°C ambient per Figure 11.

Can AL5809-40S1-7 be used in high-side configuration with AC input?

Yes - its floating ground architecture and 60V V_IN-OUT rating allow direct series connection in high-side configuration with rectified AC inputs. When used with bridge rectifiers, it withstands peak line voltages (e.g., 340V for 240VAC) when paired with appropriate series impedance and surge protection, as confirmed in Diodes' Application Note AN-02007.

Does AL5809-40S1-7 require a heatsink in SOD-123 package?

No dedicated heatsink is required, but thermal performance depends critically on PCB layout: Diodes specifies 50.8mm × 50.8mm 2oz copper with thermal vias for 0.36W dissipation. Without this, junction temperature exceeds +125°C rapidly - e.g., at 40mA and 10V drop (0.4W), ambient must stay below 40°C on standard FR-4.

How does PWM dimming interact with AL5809-40S1-7's thermal shutdown?

PWM dimming reduces average power dissipation, lowering junction temperature and delaying thermal shutdown onset. However, t_{ON_MIN} = 500µs means pulses shorter than this will not fully activate regulation - causing current droop. At 100Hz (10ms period), minimum usable duty cycle is 5%, ensuring ≥500µs on-time and avoiding thermal instability during dimming transitions.