DN05020/D Automotive LED Driver with On/Off and Dimming Control http://onsemi.com DESIGN NOTE Circuit Description Key Features This Design Note features a combination of two integrated circuits (NCV7680 and NCV7608) for driving automotive LEDs, combining the best features of both ICs. The NCV7680 creates the current source necessary to drive 8 strings of LEDs, while the NCV7608 allows the outputs to be segmented resulting in control of individual strings for On/Off control or dimming purposes. The NCV7680 provides the DC current programming via the RSTOP programming resistor. A chart is available in the datasheet for programming the current up to 75 mA. The NCV7608 On/OFF dimming control can be employed using either the SPI inputs or using the 4 parallel inputs. Control of 8 Strings of LEDs Individual On/Off Control Individual Dimming Control Open Circuit Detection Short Circuit Detection Table 1. DEVICE DETAILS Device Application Load Dump Channel Count Output LED Current per Channel Miscellaneous NCV7680, NCV7608 Automotive Lighting 40 V 8 75 mA Waveshaping Table 2. OTHER SPECIFICATIONS Others NCV7608 Output Current 800 mA Max NCV7608 SPI Frequency 5 MHz Max NCV7608 Frame Length 16 Bits Open Load Detection Yes, via NCV7608 Parallel Input for PWM Yes, via NCV7608 Slew Rate Control Yes, via NCV7608 & NCV7680 Current Programming Yes, via NCV7680 3.3 V/5 V Compatible Logic Yes, on the NCV7608 Daisy Chain Compatible Yes, on the NCV7608 AEC Q10X−12−REV A Compatible Yes, on the NCV7608 When less than 8 strings of LEDs are utilized, the additional outputs on the NCV7608 can be used as either high-side or low-side drivers. Semiconductor Components Industries, LLC, 2013 January, 2013 − Rev. 1 1 Publication Order Number: DN05020/D DN05020/D SCHEMATIC VS Vbat 14V SI SO NCV7608 D2 S2 D1 S1 D3 S3 D4 S4 D5 S5 D6 S6 C2 0.1uF D7 S7 C1 0.1uF D8 S8 VCC 5V CSB VCC SCLK IN8 IN7 IN6 IN5 EN microprocessor NCV7680 C3 0.1uF R1 10K Mode Control High, outputs on Low, outputs off R2, 3.09K OUT1 OUT2 VP OUT3 Ballast Drive OUT4 FB GND STOP OUT5 DIAG OUT6 RSTOP OUT7 RTAIL OUT8 Figure 1. Complete Schematic 1. The number of diodes in each string is determined by the users choice of component and current used. 2. Mode Control can also be used as a modulating source for contiguous usage of LEDs. 3. Power supply capacitors may need to be increased depending on the current level and duty cycle used. NCV7680 DC Current Programming The DC current of each LED string is determined by the programming resistor on RSTOP (3.09K in Figure 1) of the NCV7680. Figure 2. NCV7680 IOUT vs RSTOP http://onsemi.com 2 DN05020/D NCV7608 SPI Frame The output frame presents the output status for each individual driver, the parallel input state, and the battery supply status. The NCV7608 SPI frame consists of input control for each individual output and control for open load diagnostic enable. Figure 3. NCV7608 SPI Frame ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. SCILLC reserves the right to make changes without further notice to any products herein. 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