RT8450BGCP Richtek

RT8450/B High Voltage Multi-Topology LED Driver General Description Features zz z zz High Voltage : V Up to 40V, V Up to 50V IN OUT The RT8450/B is a current mode PWM regulator for LED zz z zz 1.5A Switch Current driving applications. With an 1.5A switch on board and wide zz z zz Buck, Boost or Buck-Boost Operation input (4.5V to 40V) and/or output (up to 50V)ranges the zz z zz Current Mode PWM with 800kHz (RT8450) and RT8450/B can operate in any of the three common 500kHz (RT8450B) Switching Frenquency topologies : Buck, Boost or Buck-Boost. zz z zz Easy Dimming : Analog, PWM Digital or PWM With 800k/500kHz operating frequency, the external PWM Converting to Analog with One External Capacitor inductor and input/output capacitors can all be small. High zz z zz Programmable Soft-Start to Avoid Inrush Current efficiency is achieved by a 190mV current sensing. zz z zz Programmable Over Voltage Protection to Limit Dimming can be done either analog or PWM signal. An Output Voltage unique built-in clampping comparator and filtering resistor zz z zz V Under Voltage Lockout and Thermal Shutdown IN allow easy low noise analog dimming conversion from zz z zz RoHS Compliant and Halogen Free PWM signal with only one external capacitor. The RT8450/B is available in a TSSOP-16 (Exposed Pad) Applications and WDFN-12L 3x3 packages. z GPS, Portable DVD Backlight z Desk Lights and Room Lighting Ordering Information z Industrial Display Backlight RT8450/B Package Type Pin Configurations CP : TSSOP-16 (Exposed Pad) QW : WDFN-12L 3x3 (W-Type) (TOP VIEW) Lead Plating System G : Green (Halogen Free and Pb Free) ISP 16 VCC1 ISN 2 15 VCC2 Switching Frequency VC 3 14 SW 500kHz ACTL 4 13 SW GND 5 DCTL 12 GND 800kHz 6 11 EN GND 17 Note : OVP 7 10 GND Richtek products are : 8 SS 9 GND RoHS compliant and compatible with the current require- TSSOP-16 (Exposed Pad) ments of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. ISP 1 12 VCC2 2 11 ISN VCC1 VC 3 10 SW GND Marking Information 4 9 ACTL GND 5 8 SS DCTL 13 67 EN OVP For marking information, contact our sales representative directly or through a Richtek distributor located in your WDFN-12L 3x3 area. DS8450/B-04 June 2011 www.richtek.com 1RT8450/B Typical Application Circuit V IN 4.5V to 40V C1 RT8450/B R2 ISP VCCx 190mV EN R3 R4 5V ISN DCTL PWM Dimming control OVP C5 VC GND R1 SS 10k L 20H ACTL C3 SW C2 10nF 3.3nF C4 0.47F Figure 1. PWM to Analog Dimming Buck Configuration V IN 4.5V to 40V C1 RT8450/B R2 190mV ISP VCCx Analog R3 R4 ISN ACTL Dimming DCTL OVP C4 EN 5V GND VC L R1 SS 15H 10k SW C3 C2 10nF 3.3nF Figure 2. Analog Dimming Buck Configuration V IN 4.5V to 40V C1 RT8450/B R2 190mV ISP VCCx R3 R4 ISN PWM ACTL Dimming control DCTL OVP EN C4 5V GND VC L R1 SS 15H 10k SW C3 C2 10nF 3.3nF Figure 3. PWM Dimming Buck Configuration Through ACTL Pin www.richtek.com DS8450/B-04 June 2011 2