RUPPER R LOWER C UPPER C LOWER DATASHEET ISL97678 FN6998 Rev.3.00 8-Channel 45V, 50mA LED Driver Sep 8, 2017 The ISL97678 is an 8-channel PWM dimming LED driver for Features LCD backlight applications. The ISL97678 is capable of driving 8 channels up to 96 pieces of 3.4V/50mA LEDs but larger numbers of LEDs are possible if the LED forward voltage combined is less 4.75V ~ 26V input than 45V. The ISL97678 has 8 channels of voltage controlled 45V maximum output current sources with typical currents matching to 1%, which Drive typically 96 LEDs (3.4V/50mA each) compensate for the non-uniformity effect of forward voltages variance in the LED strings. To minimize the voltage headroom External PWM input up to 20kHz dimming and power loss in the typical multi-string operation, the Dimming range 0.4%~100% up to 30kHz ISL97678 features dynamic headroom control that monitors the highest LED forward voltage string and uses its feedback Current matching 0.7% typical signal for output regulation. Protections - String open circuit and short circuit detections, OVP, and The ISL97678 features PWM dimming up to 30kHz with OTP 0.4%~100% duty cycle and maintains 1% current matching across all ranges. The PWM dimming frequency can be Adjustable dimming frequency adjusted between 100Hz and 30kHz. The boost switching Adjustable switching frequency frequency can also be adjusted between 600kHz and 1.5MHz. 32 Ld (5mmx5mm) QFN package The ISL97678 features extensive protection functions that include string open and short circuit detections, OVP, and OTP. Applications The ISL97678 is available in the 32 Ld QFN 5mmx5mm and Notebook displays WLED or RGB LED backlighting operate from -40C to +85C with input voltage ranges from LCD monitor LED backlighting 4.75V to 26V. Related Literature For a full list of related documents, visit our website - ISL97678 product page 45V*, 50mA per String 96 (8x12) LEDs V IN 4.75V~26V C IN 10H/3A C OUT 3x4.7F/50V 10F VIN LX EN OVP PROCESSOR PWM ISL97678 RSET CH1 R SET LED CH2 BACKLIGHT FPWM R FPWM CH8 FSW AGND PGND R FSW FIGURE 1. TYPICAL APPLICATION CIRCUIT: TFT-LCD NOTEBOOK DISPLAY FN6998 Rev.3.00 Page 1 of 17 Sep 8, 2017R R UPPER LOWER 806k 22k ISL97678 Typical Application Circuit 45V*, 50mA per String D1 L1 V * = 4.75V~26V IN 96 (8x12) LEDs Optional fuse C CIN 10H/3A OUT 3x4.7F/50V 20 21 10F VIN C 16 UPPER 100pF 17 EN OVP 23 ISL97678 C LOWER 1F 3.3nF 18 VDC CH1 25 1F 10 CH2 26 VLOGIC 50k CH3 11 FSW 27 333k FPWM 12 CH4 28 THERMAL PAD 14.2k CH5 13 RSET 29 3.3nF CH6 14 COMP 30 15k PWM CH7 4 31 2 AGND CH8 32 3 AGND PGND 1 5 AGND PGND 19 Note: V * 12V for 45V/50mA Applications IN 6 7 8 9 15 22 FIGURE 2. ISL97678 TYPICAL APPLICATION DIAGRAM FN6998 Rev.3.00 Page 2 of 17 Sep 8, 2017 AGND AGND AGND AGND LX AGND LX PGND