Synchronous Boost and Synchronous Buck LED Controllers

The MAX25601A/B/C/D is a synchronous boost controller followed by a synchronous buck LED controller. The 4.5V to 40V input voltage range of the boost controller is ideal for automotive applications, and acts as a pre-boost power supply for the second-stage buck LED controller.

The synchronous boost is a current-mode controller that can be be paralleled with another device to provide higher output power. A SYNCOUT pin provides the clock to drive the RT/SYNCIN pin of the other device, enabling two-phase 180-degree out-of-phase operation. The boost converter can be programmed with a switching frequency of 200kHz to 2.2MHz. Spread spectrum is included to reduce EMI. An internal digital soft-start feature is provided to enable a smooth power up of the boost output. Protection features like hiccup mode, overvoltage protection, and thermal shutdown are provided.

The synchronous buck LED controller uses Maxim's F3 Architecture, a proprietary average-current-mode control scheme to regulate the inductor current at a constant switching frequency without any control-loop compensation. Inductor current is sensed in the bottom synchronous n-channel MOSFET. The device operates over a wide 4.5V to 65V input range at switching frequencies as high as 1MHz. Both analog and PWM dimming are included. LED current can be monitored on the IOUTV pin.

Both controllers have high- and low-side gate drivers with at least 1A peak source and sink-current capability. Adaptive non-overlap control logic prevents shoot-through currents during transition. Both the boost and the buck faults are monitored on the active-low FLT pin.

The MAX25601A/C is available in a 32-pin SWTQFN package and the MAX25601B/D is available in a 28-pin TSSOP package. The 32-pin package features an additional switch control that can be used in high-beam/low-beam and heads-up display applications.

Applications

* Automotive Exterior Lighting: High-Beam/Low-Beam/ Signal/Position Lights, Daytime Running Lights (DRLs), Matrix Light, Pixel Light, and Other Adaptive Front-Light Assemblies * Commercial, Industrial, and Architectural Lighting

* Integration Minimizes BOM for High-Brightness LED Driver, Saving Space and Cost

* Wide Input-Voltage Range from 4.5V to 40V

* Wide Boost-Output Range up to 65V

* Programmable Switching Frequency Optimizes Component Size

* External MOSFETs Can be Sized for Appropriate Current

* Synchronous Rectification Provides High Efficiency and Fast Transient Response

* Average Current-Mode Control for Buck Eliminates Compensation Components

* Wide Dimming Ratio Allows High Contrast Ratio

* Analog Dimming and PWM Dimming

* Analog Voltage-Controlled PWM Dimming

* Protection Features and Wide Temperature Range Increase System Reliability

* Short Circuit, Overvoltage, and Thermal Protection

* -40°C to +125°C Operating Temperature Range