L99LD01: automotive LED driver STMicroelectronics SPI-configurable boost controller with detailed diagnostics The L99LD01 is a boost controller dedicated to the control of high-brightness LEDs in vehicle headlight applications. Key features - general section This device offers high software configurability and architecturetopology flexibility using a versatile platform approach. The scalable solution enables a cost-optimized selection of the power components and provides full diagnostics and protection for enhanced system reliability. QQ QQ QQ QQ QQ QQ QQ QQ QQ QQ Input voltage range: 5 to 40 V Operating junction temperature: -40 to 150 °C Adjustable switching frequency: 100 to 500 kHz Constant frequency, peak current mode control Cycle-by-cycle input current limitation Spread spectrum Ajustable input/output overvoltage protection SPI interface Software configurable maximum input current 5 V regulator with watchdog and reset control Key features - LED driver QQ QQ QQ QQ High-side current sense Enhanced high-side PWM dimming LED over-temperature detection and protection with external NTC Analog multiplexer to monitor the NTC input and LED’s forward voltage QQ QQ Protection against shorted output to GND Software configurable LED current Key benefits QQ QQ QQ QQ QQ QQ QQ QQ QQ QQ Software configurability for platform approach Enhanced and detailed diagnostics Compatible with boost, floating buck-boost and flyback topologies Operation with and without microcontroller External MOSFET for scalability Single wire to the LED strings Low electromagnetic emission Full application protection Supports fail-safe strategies (ASILB, ISO 26262) Compatible with both microcontroller and standalone configuration Main applications QQ QQ QQ LED headlamps LED signal lights LED daytime running lights www.st.com/automotive VCC 1 Vreg 5V Internal Vreg Watchdog reset Limp home VCC2 R SF R C Co mp SC EN C 5V VS Application example: L99LD01 in boost configuration Driver G1 G1 PGND ISP NRES ISN LHM Microcontroller Parameter settings Isense + SMPS control CSN SCK SDI ST SPI SDO PWM _L INP _OV Logic Control and diagnostics Charge pump Driver G2 Protection EXT _VCC CPB G2 LMODE Mux PWM MOUT Isense - L99LD01 VLED NTC GND 1 GND 2 PGND Device description The L99LD01 consists of a boost controller, which is optimized as a constant-current generator. The boost section is based on a constant switching frequency and peak current mode architecture, which provides an inherent cycle-by-cycle input current limitation. The device integrates a powerful gate driver for an n-channel switching MOSFET, and a charge pump for the control of an n-channel high-side dimming MOSFET that allows the LED string to be connected directly to ground/chassis. The L99LD01 enables full protection of the application: input and output overvoltage, temperature sensing via the NTC input with programmable current foldback and LED overcurrent protection. The SPI interface offers unique software configurability: adjustable LED current, input current limitation, PWM dimming features and dithering, and more. It also offers a detailed diagnosis of the potential application failures, and supports high functional safety requirements (ASILB according to ISO 26262) through the watchdog, the watchdog timer status and the limp home mode. The 5 V regulator (which supplies up to 20 mA), combined with the reset control and the watchdog, provides reliable power management for an 8-bit microcontroller. The L99LD01 can also operate in standalone configurations. © STMicroelectronics - March 2011 - Printed in United Kingdom - All rights reserved The STMicroelectronics corporate logo is a registered trademark of the STMicroelectronics group of companies All other names are the property of their respective owners Order code: FLL99LD010211 For more information on ST products and solutions, visit www.st.com