Automotive Exterior Lighting Solutions

The MAX20050–MAX20053 are high-brightness LED (HB LED) drivers for automotive exterior lighting applications. Consisting of a fully synchronous step-down converter with integrated MOSFETs, the devices are capable of driving a series string of LEDs at up to 2A, with a minimum number of external components. The MAX20050/ MAX20052 utilize internal loop compensation to minimize component count, while the MAX20051/MAX20053/MAX20053D use external compensation for full flexibility.

The wide 4.5V to 65V input supply range supports extreme automotive cold crank and load-dump conditions. A low- and high-switching frequency option (400kHz or 2.1MHz) provides the designer with the flexibility to optimize for solution size or efficiency, while avoiding interference within the AM band. Spread spectrum provides further options for the designer to reduce EMI at the system level. The MAX20050/MAX20051 have an internal switching frequency of 400kHz, while the MAX20052/MAX20053 have an internal switching frequency of 2.1MHz. In addition, the MAX20051B has spread spectrum disabled.

High-side current regulation means only a single connection to the LED string is required; grounding of the string can be done locally. In addition to PWM dimming, the ICs provide analog dimming using the REFI pin. Fullscale current regulation accuracy is ±2.5%, while the accuracy is ±8% at 10% of full-scale over the full temperature range of -40°C to +125°C. A 5V, 10mA LDO output is available for biasing other circuits.

Fault-protection mechanisms include output overload, short-circuit, and device overtemperature protection. The devices are specified for operation over the full -40°C to +125°C temperature range and are available in thermally enhanced 12-pin (3mm x 3mm) TDFN, 14-pin (5mm x 4.4mm) TSSOP, and 24-pin TQFN (4mm x 4mm) packages with an exposed pad.

Design Solution: Driver Monitoring Systems Need a New Breed of IR-LED Drivers ›

Applications

• Clearance Lamps (CLLs)
• Commercial, Industrial, and Architectural Lighting
• Corner Lamps (CLs)
• Daytime Running Lamps (DRLs)
• Driver Monitoring Systems (DMS)
• Fog Lamps
• Head Lamps
• Rear Lamps

The MAX20050–MAX20053 are high-brightness LED (HB LED) drivers for automotive exterior lighting applications. Consisting of a fully synchronous step-down converter with integrated MOSFETs, the devices are capable of driving a series string of LEDs at up to 2A, with a minimum number of external components. The MAX20050/ MAX20052 utilize internal loop compensation to minimize component count, while the MAX20051/MAX20053/MAX20053D use external compensation for full flexibility.

The wide 4.5V to 65V input supply range supports extreme automotive cold crank and load-dump conditions. A low- and high-switching frequency option (400kHz or 2.1MHz) provides the designer with the flexibility to optimize for solution size or efficiency, while avoiding interference within the AM band. Spread spectrum provides further options for the designer to reduce EMI at the system level. The MAX20050/MAX20051 have an internal switching frequency of 400kHz, while the MAX20052/MAX20053 have an internal switching frequency of 2.1MHz. In addition, the MAX20051B has spread spectrum disabled.

High-side current regulation means only a single connection to the LED string is required; grounding of the string can be done locally. In addition to PWM dimming, the ICs provide analog dimming using the REFI pin. Fullscale current regulation accuracy is ±2.5%, while the accuracy is ±8% at 10% of full-scale over the full temperature range of -40°C to +125°C. A 5V, 10mA LDO output is available for biasing other circuits.

Fault-protection mechanisms include output overload, short-circuit, and device overtemperature protection. The devices are specified for operation over the full -40°C to +125°C temperature range and are available in thermally enhanced 12-pin (3mm x 3mm) TDFN, 14-pin (5mm x 4.4mm) TSSOP, and 24-pin TQFN (4mm x 4mm) packages with an exposed pad.

Design Solution: Driver Monitoring Systems Need a New Breed of IR-LED Drivers ›

Applications

• Clearance Lamps (CLLs)
• Commercial, Industrial, and Architectural Lighting
• Corner Lamps (CLs)
• Daytime Running Lamps (DRLs)
• Driver Monitoring Systems (DMS)
• Fog Lamps
• Head Lamps
• Rear Lamps

The LT8376 is a monolithic, synchronous, step-down DC/DC converter that utilizes fixed-frequency, peak current control and provides PWM dimming for a string of LEDs. The LED current is programmed by an analog voltage or the duty cycle of pulses at the CTRL pin. An output voltage limit can be set with a resistor divider to the FB pin.

The switching frequency is programmable from 200kHz to 2MHz by an external resistor at the RT pin or by an external clock at the SYNC/SPRD pin. With the optional spread spectrum frequency modulation enabled, the frequency varies from 100% to 125% to reduce EMI. The LT8376 also includes a driver for an external, high side PMOS for PWM dimming and an internal PWM signal generator for analog control of PWM dimming when an external signal is not available.

Additional features include an LED current monitor, an accurate EN/UVLO pin threshold, open-drain fault reporting for open-circuit and short-circuit load conditions, and thermal shutdown. The LT8376 utilizes the proprietary Silent Switcher technology for very low EMI.

APPLICATIONS

• Automotive Lighting
• Industrial and General Purpose Lighting

The MAX20078 is a high-voltage, synchronous n-channel MOSFET controller for high-current buck LED drivers. The device uses a proprietary average current-mode-control scheme to regulate the inductor current. This control method does not need any control-loop compensation while maintaining nearly constant switching frequency. Inductor current sense is achieved by sensing the current in the bottom synchronous n-channel MOSFET. It does not require any current sense at high voltages. The device operates over a wide 4.5V to 65V input range. The device is designed for high-frequency operation and can operate at switching frequencies as high as 1MHz. The high- and low-side gate drivers have peak source and sink current capability of 2A. The driver block also includes a logic circuit that provides an adaptive nonoverlap time to prevent shoot-through currents during transition. The device includes both analog and PWM dimming. The device includes a 5V V_CC regulator capable of delivering 10mA to external circuitry. The device also includes a current monitor that provides an analog voltage proportional to the inductor current. The device has a fault flag that indicates open and shorts across the output. Protection features include inductor current-limit protection, overvoltage protection, and thermal shutdown. The MAX20078 is available in a space-saving (3mm × 3mm), 16-pin TQFN or a 16-pin TSSOP package and is specified to operate over the -40°C to +125°C automotive temperature range.

Design Solution: Driver Monitoring Systems Need a New Breed of IR-LED Drivers ›

Design Solution: Achieve Superior Automotive Exterior Lighting with a High-Power Buck LED Controller ›

Applications

• Automotive Front Lights
• Automotive Matrix Lights
• Constant-Current Regulators
• Head-Up Displays

The MAX20096/MAX20097 are dual-channel, high-voltage, synchronous n-channel high-current buck LED drivers. The ICs use a proprietary average current-mode-control scheme to regulate the inductor current. This control method does not require any control-loop compensation, maintaining nearly constant switching frequency. Inductor current sense is achieved by sensing the current in the bottom switching device. The ICs integrate two fully synchronous buck-converter controllers, and operate over a wide 4.5V to 65V input range. The ICs are designed for high-frequency operation and can operate at switching frequencies as high as 1MHz.

In the MAX20096, the output voltages and currents on both channels and the junction temperature can be read back through the SPI interface. Protection features include inductor current-limit protection, overvoltage protection, and thermal shutdown. The MAX20096 is available in a space-saving thermally enhanced (5mm × 5mm), 32-pin side-wettable TQFN package and is specified to operate over the -40°C to +125°C automotive temperature range.

The MAX20097 is available in a 28-pin thermally enhanced TSSOP package, but does not have the SPI interface. It includes an open-drain fault flag (FLTB) that goes low in case of an open string, shorted string, or overvoltage activation in any one of the channels, or also in thermal shutdown.

Applications

• Automotive Exterior Lighting
• Commercial, Industrial, and Architectural Lighting
• Daytime Running Lights (DRLs)
• Fog Light and Adaptive Front Light Assemblies
• High-Beam/Low-Beam/Signal/Position Lights

The MAX20096/MAX20097 are dual-channel, high-voltage, synchronous n-channel high-current buck LED drivers. The ICs use a proprietary average current-mode-control scheme to regulate the inductor current. This control method does not require any control-loop compensation, maintaining nearly constant switching frequency. Inductor current sense is achieved by sensing the current in the bottom switching device. The ICs integrate two fully synchronous buck-converter controllers, and operate over a wide 4.5V to 65V input range. The ICs are designed for high-frequency operation and can operate at switching frequencies as high as 1MHz.

In the MAX20096, the output voltages and currents on both channels and the junction temperature can be read back through the SPI interface. Protection features include inductor current-limit protection, overvoltage protection, and thermal shutdown. The MAX20096 is available in a space-saving thermally enhanced (5mm × 5mm), 32-pin side-wettable TQFN package and is specified to operate over the -40°C to +125°C automotive temperature range.

The MAX20097 is available in a 28-pin thermally enhanced TSSOP package, but does not have the SPI interface. It includes an open-drain fault flag (FLTB) that goes low in case of an open string, shorted string, or overvoltage activation in any one of the channels, or also in thermal shutdown.

Applications

• Automotive Exterior Lighting
• Commercial, Industrial, and Architectural Lighting
• Daytime Running Lights (DRLs)
• Fog Light and Adaptive Front Light Assemblies
• High-Beam/Low-Beam/Signal/Position Lights

The MAX20051 evaluation kit (EV kit) demonstrates the MAX20051 and MAX20053, 2A synchronous buck LED drivers with integrated MOSFETs.

The EV kit operates from a DC supply voltage from 4.5V to 65V and the switching frequency is fixed at 400kHz. Spread-spectrum mode (SSM) is enabled for EMI improvement. The EV kit demonstrates both analog and pulse-width modulation (PWM) dimming. The EV kit also demonstrates short LED, open LED, and overtemperature- fault protection.

The EV kit also comes with a MAX20053 IC, which can be installed to evaluate the 2.1MHz switching frequency device. Refer to the Evaluating the MAX20053 section for more information.

Applications

• Clearance Lamps (CLLs)
• Commercial, Industrial, and Architectural Lighting
• Corner Lamps (CLs)
• Daytime Running Lamps (DRLs)
• Fog Lamps
• Head Lamps
• Rear Lamps

The MAX25601 evaluation kit (EV kit) provides a proven design to evaluate the MAX25601A/MAX25601C automotive high-voltage, high-brightness LED (HB LED) boost-buck controller. The front-end pre-boost operates from a 7.7V to 18V DC supply voltage, generating a 48V output. The buck supports 12x LEDs and lower, delivering up to 1.5A to one string of LEDs. The total voltage of the string can vary from 3V to 36V.

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

Evaluation board EVAL-LT8376-AZ is a 60V, 2A synchronous Buck LED driver featuring the LT8376. EVAL-LT8376-AZ drives a single string of LEDs up to 36V at 1.5A when V_IN is between 43V and 57V. EVAL-LT8376-AZ has an undervoltage lockout (UVLO) set at 40V with 2V hysteresis for turn-on. EVAL-LT8376-AZ runs at 350kHz switching frequency and features optional spread spectrum modulation (SSFM). With SSFM enabled, LT8376 modulates its switching frequency from f_SW to f_SW + 25% to reduce EMI emissions.

The LT8376 has an input voltage range of 3.6V to 60V. LT8376 has internal, synchronous 60V switches for high efficiency and small size. LT8376 has an adjustable switching frequency between 200kHz and 2MHz. The LT8376 can be synchronized with an external clock source or configured with SSFM enabled for low EMI. EVAL-LT8376-AZ includes a SYNC/SSFM jumper to configure the LT8376 for either external frequency synchronization, SSFM enabled for low EMI, or set to normal operation with SSFM disabled.

The LT8376’s integrated PWMTG high-side PMOS driver assists with PWM dimming of the connected LEDs. The LED string can be PWM dimmed for accurate brightness control with an externally generated PWM signal or an internally-generated PWM signal. EVAL-LT8376-AZ has jumpers that can be set to switch between internally-generated PWM signal, externally generated PWM signal, and 100% on with no PWM signal. The LT8376 can also be analog dimmed by placing a controllable DC voltage on the CTRL pin. When running PWM dimming with SSFM enabled, the SSFM aligns itself with the PWM signal for flicker-free operation of the LED string. This applies to both internal and external PWM dimming.

Small ceramic input and output capacitors are used to save space and cost. The input and output filters on EVAL-LT8376-AZ reduce its EMI. The filters consist of a small ferrite bead or inductor and high frequency ceramic capacitors. These filters, combined with proper board layout and SSFM, are very effective in reducing EMI to comply with CISPR25 class 5 limits. Please follow the recommended layout and the four-layer PCB thickness of EVAL-LT8376-AZ. For best efficiency and PWM dimming performance, the EMI filters at the input and output can be removed.

The open LED overvoltage protection (OVP) uses the IC’s constant voltage regulation loop to regulate the output to approximately 41V if the LED string is opened. The output current can be monitored through the ISMON pin. Also, the FAULT pin can be used for open and short detection.

The input undervoltage lockout (UVLO), LED current, output overvoltage protection (OVP), and switching frequency, can all be easy adjusted with simple modifications to EVAL-LT8376-AZ.

The LT8376 data sheet gives a complete description of the device, operation, and applications information. The data sheet must be read in conjunction with this demo manual for evaluation board EVAL-LT8376-AZ. The LT8376RV is assembled in a 28-lead plastic LQFN package with a thermally enhanced exposed ground pad. Proper board layout is essential for maximum performance. See the data sheet section “Designing the Printed Circuit Board”.

The MAX20078 evaluation kit (EV kit) provides a proven design to evaluate the MAX20078 synchronous buck controller for high-power, high-brightness (HB) LED drivers. The EV kit is set up as a buck LED driver and operates from a 4.5V to 65V DC supply voltage. The EV kit is configured to deliver up to 2A to one string of LEDs. The total voltage of the string can vary from 3V to 55V. The anode of the LED string should be connected to the LED+ terminal and the cathode of the LED string connected to PGND.

Applications

• Automotive Front Lights
• Automotive Matrix Lights
• Constant-Current Regulators
• Head-Up Displays

The MAX20096 evaluation kit (EV kit) provides a proven design to evaluate the MAX20096 dual-channel synchronous buck, high-brightness LED controller with and without SPI interface for high-power HB LED drivers. The EV kit is set up as a dual-buck LED driver and operates from a 4.5V to 65V DC supply voltage. The EV kit is configured to deliver up to 3A in each string of LEDs for both channels. The total voltage of the string can vary from 3V to 55V. The anode of the LED string should be connected to the LED+ terminal; the cathode should be connected to PGND.

Applications

• Automotive Exterior Lighting
• Commercial, Industrial, and Architectural Lighting
• Daytime Running Lights (DRLs)
• Fog Light and Adaptive Front Light Assemblies
• High-Beam/Low-Beam/Signal/Position Lights

The MAX20097 evaluation kit (EV kit) provides a proven design to evaluate the MAX20097 dual-synchronous buck controller for high-power, high-brightness (HB) LED drivers. The EV kit is set up as a dual-buck LED driver and operates from a DC supply voltage from 4.5V to 65V. The EV kit is configured to deliver up to 2A of current through the LEDs for both the channels. The total voltage of each of the 2 LED strings can vary from 3V to 55V.

Applications

• Automotive Exterior Lighting
• Commercial, Industrial, and Architectural Lighting
• Daytime Running Lights (DRLs)
• Fog Light and Adaptive Front Light Assemblies
• High-Beam/Low-Beam/Signal/Position Lights

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

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