Analog Devices Inc. DC1309A

Overview

DC1309A from Analog Devices (formerly Linear Technology) is a demonstration circuit board featuring the LT3474-1 36V step-down 1A LED driver IC, designed to drive high-voltage LED strings up to 26V with constant-current regulation. It implements open-LED protection via an external 24V zener clamp (D4), supports analog and PWM dimming, and achieves 90.4% efficiency at 32V_IN driving an 8-LED, 23V, 1A string.

For engineers reviewing the DC1309A datasheet, DC1309A pinout, DC1309A application, or DC1309A equivalent, key selection considerations include its fixed 24V overvoltage clamp level, TSSOP-16 FE layout compatibility with LT3474-1, thermal pad grounding requirements, and modifiability for PWM dimming via Q1/Q2 MOSFET placement.

Technical Context

DC1309A implements a current-mode controlled buck topology using the LT3474-1 IC, operating up to 36V input and delivering regulated 1A output current. It incorporates frequency foldback during overload and thermal shutdown for fault protection, with open-LED detection enabled by the D4 zener-based clamp set to 24V.

The board supports dual dimming methods: analog control via the CTRL pin and external PWM switching at the LED cathode. Layout includes a thermally enhanced ground pad under the LT3474-1's TSSOP-16 FE package, requiring proper copper pour and via stitching per the datasheet's Layout Hints section.

Key Specifications

Availability

DC1309A is available at Aetrix Electronics and suitable for LED lighting evaluation, automotive headlight prototyping, and industrial signage development requiring stable component supply and validated reference design support.

Supply support for DC1309A 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

Analog Devices (acquired Linear Technology in 2017) is a global semiconductor company specializing in high-performance analog, mixed-signal, and power management solutions.

The DC1309A belongs to Linear's demonstration circuit series for LED drivers, engineered to accelerate validation of LT3474-1–based constant-current buck converters in high-brightness lighting applications.

FAQ

What is the primary function of DC1309A?

DC1309A is a fully assembled demonstration circuit board built around the LT3474-1 IC to evaluate its performance as a 36V input, 1A constant-current step-down LED driver. It provides a ready-to-test platform with verified layout, thermal design, and protection features including 24V open-LED clamping, making DC1309A ideal for rapid prototyping of high-voltage LED strings.

How is overvoltage protection implemented on DC1309A?

DC1309A implements overvoltage protection using an external zener diode (D4) configured as a clamp across the LED string, set to 24V. This threshold prevents damage during open-circuit conditions while allowing full utilization of the LT3474-1's extended 26V output capability-unlike the LT3474's internal 13V clamp. Replacing D4 adjusts the clamp level on DC1309A.

Can DC1309A support PWM dimming, and how is it enabled?

Yes, DC1309A supports PWM dimming through hardware modification: connect the LED string cathode to LED− instead of GND, then populate either Q1 or Q2 with a suitable MOSFET. This configuration allows external PWM signals to switch the LED current path. The base configuration uses analog dimming via the CTRL pin, so DC1309A offers dual dimming flexibility depending on implementation.

What thermal design features does DC1309A include for the LT3474-1?

DC1309A uses the LT3474-1 in a 16-lead TSSOP FE package with an exposed thermal pad, and the board implements a dedicated ground plane with multiple thermal vias beneath the IC. This layout follows the datasheet's 'Layout Hints' to maximize heat dissipation-critical because high-output-power operation (e.g., 26V LED strings) can cause significant IC self-heating on DC1309A.

Is DC1309A compatible with both LT3474 and LT3474-1 ICs?

No-DC1309A is specifically configured for the LT3474-1, which lacks the internal 13V output clamp present in the LT3474. The 24V external clamp on DC1309A aligns with the LT3474-1's higher 26V output capability. Substituting the LT3474 would limit usable LED string voltage and risk overvoltage failure, so DC1309A is not cross-compatible with the LT3474.