Renesas IW3637-31

Overview

The IW3637-31 from Renesas Electronics is a high-performance off-line LED driver controller for buck topology applications, featuring analog 0–1.8V dimming interface (DIM2), disabled internal OTP, and 100ms light-off delay. It delivers ±3% output current regulation via PrimAccurate™ sensing, supports up to 150W output power in SOIC-8, and operates with VCC from 7.5V to 30V. Used in commercial T8 and 0–10V dimmable LED drivers.

For engineers reviewing the IW3637-31 datasheet, IW3637-31 pinout, IW3637-31 application, or IW3637-31 equivalent, key selection considerations include its analog dimming configuration (0–1.8V on NTC/DIM2), absence of internal over-temperature protection, buck-only topology support, and soft-off functionality before light-off mode.

Technical Context

The IW3637-31 implements quasi-resonant PWM control with configurable switching frequencies of 72kHz or 90kHz, enabling high-efficiency operation in non-isolated buck converters fed by front-end boost stages or rectified AC. Its PrimAccurate™ sensing eliminates need for direct current/voltage feedback components and external loop compensation.

It integrates active start-up using depletion-mode FETs, supports fast dimming transient response, and provides fault protections including output open, over-voltage, short-circuit, and input under-voltage detection - all while maintaining stable regulation across -40°C to +150°C junction temperature range.

Key Specifications

Pinout & Package

Package: SOIC-8 (standard 150-mil body, 1.27mm pitch), JEDEC MS-012AC compliant, θJA = 170°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IW3637-03 and UCC28810DR, the IW3637-31 uniquely combines analog dimming, buck-only optimization, and disabled OTP - enabling custom thermal management while retaining full dimming flexibility and flicker-free performance down to 1%.

Availability

IW3637-31 is available at Aetrix Electronics and suitable for 0–10V dimmable LED drivers, commercial T8 fixtures, and wireless smart lighting applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for IW3637-31 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

Renesas Electronics is a global semiconductor leader delivering microcontrollers, analog power, and SoC solutions for automotive, industrial, and IoT markets.

The IW3637 product line targets high-efficiency, low-flicker LED lighting systems requiring integrated dimming interfaces and minimal external components - specifically optimized for cost-sensitive commercial and industrial SSL applications.

FAQ

What topology does the IW3637-31 support?

The IW3637-31 supports buck topology only, as confirmed in the Ordering Information table. It is not qualified for flyback operation - unlike IW3637-05. The device requires either a front-end boost converter or rectified AC input, and its pinout and protection features are optimized for non-isolated buck LED driver designs. IW3637-31 does not implement flyback-specific control logic or isolation-related safety features.

Does the IW3637-31 include internal over-temperature protection?

No, the IW3637-31 has internal OTP disabled, as specified in the Ordering Information table. Thermal protection must be implemented externally - for example, by connecting an NTC thermistor to the NTC/DIM2 pin and configuring appropriate voltage thresholds. This differs from IW3637-02 (NTC-enabled) and IW3637-01 (PWM-enabled), both of which include functional internal OTP circuits.

What dimming interfaces are supported by the IW3637-31?

The IW3637-31 supports two independent dimming interfaces: a primary PWM input on DIM1 (Pin 8) and a secondary analog 0–1.8V input on NTC/DIM2 (Pin 1). Unlike variants with PWM or NTC functions on Pin 1, the IW3637-31 configures that pin exclusively for analog dimming - enabling smooth, jitter-free intensity control without MCU timing dependencies. No digital I²C or DALI interface is supported.

What is the purpose of the 100ms light-off delay in the IW3637-31?

The 100ms light-off delay in the IW3637-31 controls the fade-out time before entering ultra-low-power light-off mode. During this interval, the IC gradually reduces LED current to eliminate visible flicker or pop-on/pop-off artifacts. This behavior is factory-programmed and matches the timing used in IW3637-01 and IW3637-05 - but differs from IW3637-01A and IW3637-03A, which have no delay.

Can the IW3637-31 be used with a rectified AC input directly?

Yes, the IW3637-31 can be used with rectified AC input directly, as shown in Figure 3.2 of the Product Summary. It employs an active start-up scheme using a depletion-mode FET controlled via VIN (Pin 7), allowing reliable initialization without auxiliary winding or startup resistor. However, input ripple must be minimized - typically via bulk capacitance - to maintain stable regulation and avoid low-frequency flicker.