EVALUATION KIT AVAILABLE MAX17061A 8-String White LED Driver with SMBus for LCD Panel Applications General Description Features Accurate Dimming Control Using SMBus, PWM The MAX17061A is a high-efficiency driver for white Interface lightemitting diodes (LEDs). It is designed for large liquid- Dimming Range with 8-Bit Resolution crystal displays (LCDs) that employ an array of LEDs as Adjustable DPWM Frequency with 1.5% Accuracy the light source. An internal switch current-mode step-up controller drives the LED array, which can be configured Up to Eight Parallel Strings Multiple Series- for up to eight strings in parallel and 10 LEDs per string. Connected LEDs Each string is terminated with ballast that achieves 1.5% 1.5% Current Regulation Accuracy Between Strings current-regulation accuracy between strings, ensuring Low String Feedback Voltage: 625mV at 25mA LED even LED brightness. The MAX17061A has a wide input Current voltage range from 7.5V to 26V, and provides a fixed Full-Scale LED Current Adjustable from 15mA to 25mA or adjustable 15mA to 30mA full-scale LED current. 30mA, or Preset 25mA Open and Short LED Protections The MAX17061A internally generates a DPWM signal for accurate WLED dimming control. The DPWM frequency Output Overvoltage Protection is resistor programmable, while DPWM duty cycle is co 0.15 Internal HV Power MOSFET (45V max) trolled directly from an external PWM signal or through a Wide Input-Voltage Range from 4.5V to 26V control word through the MAX17061As SMBus inter- 500kHz/750kHz/1MHz Selectable Switching face. This DPWM control provides a dimming range with Frequency 8-bit resolution and supports Intel display-power-saving Small 28-Pin, 4mm x 4mm, Thin QFN package technology (DPST) to maximize battery life. Applications The MAX17061A has multiple features to protect the Notebook, Subnotebook, and Tablet Computer controller from fault conditions. Separate feedback loops Displays limit the output voltage under any circumstance, ensuring Handy Terminals safe operation. Once an open string is detected, the string is disabled while other strings operate normally. The MAX17061A also features short LED detection. The Simplified Operating Circuit shorted strings are also disabled after a 2ms fault blanking interval. The controller features cycle-by-cycle L1 D1 V OUT V IN current limit to provide stable operation and soft-start capability. If the MAX17061A is in current-limit condition, the step-up converter is latched off after an internal timer IN V DD V expires. A thermal-shutdown circuit provides another level CC V LX1, 2 CC 5V ISET of protection. PGND1, 2 R1 The MAX17061As step-up controller features an internal OV CCV 150m (typ), 45V (max) power MOSFET with local current- R2 MAX17061A sense amplifier for accurate cycle-by-cycle current limit. This architecture greatly simplifies the external circuitry PWM PWMI PWMO and saves PCB space. Low-feedback voltage at each LED FB1 FB2 GND string 625mV (typ) at 25mA LED current helps reduce FB3 N.C. OSC FB4 power loss and improve efficiency. The MAX17061A fea- FB5 CLK SCL tures selectable switching frequency (500kHz, 750kHz, or FB6 DATA SDA FB7 1MHz), which enables a wide variety of applications that FSET FB8 can trade off component size for operating frequency. EP The MAX17061A is available in a thermally enhanced 28-pin, 4mm x 4mm Thin QFN package. Ordering Information and Pin Description appear at end of SMBus is a trademark of Intel Corp. data sheet. 19-4485 Rev 1 11/14MAX17061A 8-String White LED Driver with SMBus for LCD Panel Applications Absolute Maximum Ratings IN to GND ..............................................................-0.3V to +28V Continuous Power Dissipation (T = +70C) A FB , LX to GND ..................................................-0.3V to +45V 28-Pin Thin QFN (derate 16.9mW/C above +70C) ...1667mW PGND to GND ....................................................-0.3V to +0.3V Operating Temperature Range ........................... -40C to +85C V , V , PWMI, SDA, SCL to GND .....................-0.3V to +6V Junction Temperature ......................................................+150C CC DD ISET, CCV, PWMO, FSET, OSC, Storage Temperature Range .............................60C to +150C OV to GND ..............................................-0.3V to V + 0.3V Lead Temperature (soldering, 10s) .................................+300C CC Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Electrical Characteristics (Circuit of Figure 1. V = 12V, C = 0.022F, R = 5.1k, V = V = V = V = 5V, R = 464k, V = GND, IN CCV CCV ISET OSC DD CC FSET PWMI T = 0C to +85C, unless otherwise noted. Typical values are at T = +25C.) A A PARAMETER CONDITIONS MIN TYP MAX UNITS IN Input Voltage Range 7.5 26 V Rising edge 7.08 7.2 7.32 IN UVLO Threshold V Falling edge 6.86 6.98 7.1 MAX17061A is enabled 70 110 IN Input Current V = 26V A IN MAX17061A is disabled, T = +25C +1 +1 A V Input Voltage 4.5 5 5.5 V CC V UVLO Threshold Rising edge, typical hysteresis = 10mV 4.00 4.25 4.45 V CC V Quiescent Current MAX17061A is enabled 1.24 2 mA CC V Shutdown Current MAX17061A is disabled 10 A CC BOOST CONVERTER LX On-Resistance 20mA from LX to PGND 0.15 0.3 LX Leakage Current 45V on LX , T = +25C 1 A A V = V 0.9 1.0 1.1 MHz OSC CC Operating Frequency V = open 675 750 825 OSC kHz V = GND 450 500 550 OSC OSC High-Level Threshold V - 0.4 V CC OSC Midlevel Threshold 1.5 V - 2.0 V CC OSC Low-Level Threshold 0.4 V Minimum Duty Cycle PWM mode (Note 1) 10 % Maximum Duty Cycle 94 95.5 97 % LX Current Limit Duty cycle = 75% (Note 1) 1.6 A CONTRL INPUT SDA, SCL Logic Input High Level 2.1 SDA, SCL Logic Input Low Level 0.8 V PWMI Logic Input High Level 2.1 V PWMI Logic Input Low Level 0.8 V Maxim Integrated 2 www.maximintegrated.com