RT8577A High Voltage 4-CH LED Driver General Description Features Wide Input Supply Voltage Range : 5.5V to 40V The RT8577A is an 4-CH LED driver capable of delivering Adjustable Boost Controller Switching Frequency 120mA for each channel. The RT8577A is a current mode from 200kHz to 2.1MHz boost converter with an adjustable switching frequency Programmable Channel Current via the RT pin from 200kHz to 2.1MHz and a wide VIN Channel Current Matching : 1.5% range from 5.5V to 40V. External Dimming Control The PWM output voltage loop selects and regulates the Boost MOSFET Over Current Protection LED pin with the highest voltage string to 0.6V, hence Automatic LED Open/Short Protection to Avoid allowing voltage mismatches between LED strings. The Output Over Voltage RT8577A automatically detects and disconnects any VCC Under Voltage Lockout unconnected and/or broken strings during operation from Adjustable Over Voltage Protection PWM loop to prevent V from over voltage. The 1.5% OUT Thermal Shutdown Protection matched LED currents on all channels are simply Abnormal Status Indicator for OVP/Short/OTP programmed with a resistor. A very high contrast ratio true Condition digital PWM dimming can be achieved by driving the PWM AEC-Q100 Grade 3 Certification pin with a PWM signal. RoHS Compliant and Halogen Free When an abnormal situation (OVP/short/OTP) occurs, a status signal will be sent to the system to shut down the Applications IC. Automotive Infotainment LCD TV, Monitor Display Backlight Ordering Information LED Driver Application RT8577A Package Type General Purpose Constant Current Source QW : WQFN-20L 5x5 (W-Type) Lead Plating System Pin Configurations G : Green (Halogen Free and Pb Free) (TOP VIEW) Note : Richtek products are : RoHS compliant and compatible with the current require- 20 19 18 17 16 ments of IPC/JEDEC J-STD-020. 1 15 Suitable for use in SnPb or Pb-free soldering processes. GND STATUS 2 14 GND VCC GND 3 13 NC GND Marking Information 4 12 LED3 CREG RT8577AGQW : Product Number LED4 5 11 DRV 21 YMDNN : Date Code RT8577A 6 78 9 10 GQW YMDNN WQFN-20L 5x5 Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS8577A-01 December 2015 www.richtek.com 1 OVP LED2 RISET LED1 RT NC EN PWM SEN VCRT8577A Functional Pin Description Pin No. Pin Name Pin Function 1, 2, 3, Ground. The exposed pad must be soldered to a large PCB and connected to GND 21 (Exposed pad) GND for maximum power dissipation. Channel 3 and Channel 4 LED Current Sinks. Leave the pins unconnected if not 4, 5 LED4, LED3 used. Over-Voltage Detection Input. The Boost converter turns off when V goes OVP 6 OVP higher than 2V. LED Current Set Pin. A resistor or a current from DAC on this pin programs the 7 RISET full LED current. Switching Frequency Set. Connect a resistor between RT and GND to set the 8 RT boost converter switching frequency. 9 EN Enable Control Input. When EN is pulled low, the chip will be shut down. Current Sense Input. During normal operation, this pin senses the voltage 10 SEN across the external inductor current sensing resistor for peak current mode control and also to limit the inductor current during every switching cycle. Boost Converter Power Switch Gate Output. This pin drives the external power 11 DRV N-MOSFET device. Regulator Output for Chip Internal use Only. A 1F capacitor should be placed 12 CREG on this pin to stabilize the 5V output of the internal regulator. 13, 18 NC No Internal Connection. Power Supply of the Chip. For good bypass, a low ESR capacitor close to the 14 VCC pin is required. 15 STATUS Status Indicator Output. This pin will be pulled to low if fault happens. 16 VC PWM Boost Converter Loop Compensation Node. 17 PWM Dimming Control Input. 19 LED1 Channel 1 LED Current Sink, Leave this pin unconnected if it is not used. 20 LED2 Channel 2 LED Current Sink, Leave this pin unconnected if it is not used. Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS8577A-01 December 2015 2