RT8576 High Voltage 8-CH LED Driver General Description Features The RT8576 is an 8-CH LED driver capable of delivering 120mA for each channel. The RT8576 is a current mode boost converter with an adjustable switching frequency via the OSC pin from 100kHz to 1MHz and a wide VIN range from 9V to 28V. z The PWM output voltage loop selects and regulates the LED pin with the highest voltage string to 0.6V, hence allowing voltage mismatches between LED strings. The RT8576 automatically detects and disconnects any unconnected and/or broken strings during operation from PWM loop to prevent VOUT from over voltage. z z z z z z z z z The 3% matched LED currents on all channels are simply programmed with a resistor. A very high contrast ratio true digital PWM dimming can be achieved by driving the PWM pin with a PWM signal. When an abnormal situation (open/short/thermal) occurs, a state signal will be sent to the system to shut down the IC. z z z Wide Input Supply Voltage Range : 9V to 28V Adjustable Boost Controller Switching Frequency from 100kHz to 1MHz Programmable Channel Current Channel Current Matching : ±3% External Dimming Control Boost MOSFET Over Current Protection Automatic LED Open/Short Protection to Avoid Output Over Voltage VIN Under Voltage Lockout Adjustable Over Voltage Protection Under Voltage Protection Thermal Shutdown Protection Abnormal State Indicator for Open/Short/Thermal Condition RoHS Compliant and Halogen Free Applications z LCD TV, Monitor Display Backlight LED Driver Application General Purpose Constant Current Source The RT8576 is available in TSSOP-24 (Exposed Pad) and SOP-24 packages. z Ordering Information Marking Information RT8576 RT8576GCP Package Type CP : TSSOP-24 (Exposed Pad) S : SOP-24 Lead Plating Systeme G : Green (Halogen Free and Pb Free) Note : Richtek products are : ` RoHS compliant and compatible with the current require- z RT8576GCP : Product Number RT8576 GCPYMDNN YMDNN : Date Code RT8576GS RT8576GS : Product Number RT8576 GSYMDNN YMDNN : Date Code ments of IPC/JEDEC J-STD-020. ` Suitable for use in SnPb or Pb-free soldering processes. DS8576-00 April 2011 www.richtek.com 1 RT8576 Pin Configurations (TOP VIEW) PWM OUT1 OUT2 OUT3 OUT4 GND OUT6 OUT7 OUT8 OUT5 OVS ISET STATE NC COMP NC SS VIN PGND VCCA EXT CS EN OSC 24 2 23 3 22 4 21 5 20 GND 6 7 19 18 8 17 9 16 10 15 25 11 12 14 13 PWM OUT1 OUT2 OUT3 OUT4 GND OUT8 OUT6 OUT7 OVS ISET OSC 24 TSSOP-24 (Exposed Pad) 2 23 3 22 4 21 5 20 6 19 7 18 8 17 9 16 10 15 11 14 12 13 STATE NC COMP NC SS VIN PGND VCCA EXT OUT5 CS EN SOP-24 Typical Application Circuit VIN 9 to 28V L1 10µH D1 CIN 47µF VIN CVIN 1µF ROVP1 82k RT8576 : : : …… : : : : : : : : : : : : …… : : : : : COUT 4.7µF x 8 OUT1 RF 100 CS CF 1nF RSENSE ROVP2 3.6M …… MSW OVS VOUT 45V OUT4 OUT5 OUT6 EXT 5 …… REXT OUT8 PWM Signal Chip Enable 1k 1k RSTATE 100k PWM EN STATE ISET OSC RC 560 CC1 0.22µF CC2 NC SS COMP RISET 4.53k VIN FLT ROSC 56k CSS 0.1µF CREG 1µF VCCA PGND GND Figure 1. General Application www.richtek.com 2 DS8576-00 April 2011 RT8576 FLT VIN 9 to 28V L1 10µH D1 VOUT 45V CIN 47µF CVIN 1µF VIN RT8576 : : : : : : : …… : : : : : : : : …… : : : : : OUT1 RF 100 CS CF 1nF RSENSE ROVP1 82k COUT 4.7µF x 8 …… MSW OVS ROVP2 3.6M OUT4 OUT5 OUT6 EXT 5 OUT8 PWM Signal Chip Enable RC 560 CC1 0.22µF …… REXT CC2 NC 1k 1k PWM EN STATE ISET OSC COMP RSTATE 100k SS VIN FLT RISET 4.53k ROSC 56k CSS 0.1µF CREG 1µF VCCA PGND GND Figure 2. External P-MOSFET Isolation Application DS8576-00 April 2011 www.richtek.com 3 RT8576 Functional Pin Description Pin No. TSSOP-24 SOP-24 (Exposed Pad) Pin Name 1 1 PWM 2, 3, 4, 5 2, 3, 4, 5 6, 25 (Exposed Pad) 6 10, 7, 8, 9 15, 8, 9, 7 11 10 OVS 12 11 ISET 13 12 OSC 14 13 EN OUT1 to OUT4 GND OUT5 to OUT8 Pin Function Digital Dimming Control. Connect a pull high or pull low resistor from this pin to ground. Channel 4 to Channel 1 LED Current Sink. Leave the pins unconnected if not used. Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. Channel 8 to Channel 5 LED Current Sink. Leave the pins unconnected if not used. Over Voltage and Under Voltage Protection. PWM boost converter turns off when VOVP or VUVP goes higher than 1.2V or lower than 0.6V, respectively. LED Current Setting Pin. A resistor or a current from DAC on this pin programs the full LED current. Switching Frequency Setting Pin. Connect a resistor between OSC and GND to set the boost converter switching frequency. Chip Enable. When EN is pulled low, chip will be in shutdown mode. Current Sense Input. During normal operation, this pin senses the voltage across the external inductor current sensing resistor for peak current mode control and is also used to limit the inductor current during every switching cycle. Boost Converter Power Switch Gate Output. This pin drives the external power N-MOSFET device. 1μF capacitor should be placed on this pin to stabilize the 5V output of the internal regulator. This regulator is for chip internal use only. 15 14 CS 16 16 EXT 17 17 VCCA 18 18 PGND 19 19 VIN 20 20 SS 21, 23 21, 23 NC No Internal Connection. 22 22 COMP PWM Boost Converter Loop Compensation Node. 24 24 STATE Boost Converter Operation State Output. www.richtek.com 4 Boost Converter Power Ground. Power Supply of the Chip. For good bypass, a low ESR capacitor placed close to the pin is required. Soft-Start Pin. Place a capacitor of at least 10nF from this pin to GND to set the soft-start time period. DS8576-00 April 2011 RT8576 Function Block Diagram EXT CS OSC OSC VIN OVP - UVLO UVP OTP S + R OVS + 1.2V R LED Short + OUT1 UVP + - EN - 5V LDO COMP Shutdown + + - 1.2V 5V OUT8 VOUT Regulation Unit 6µA ………………… 0.6V VCCA STATE + - + SS - GND PGND PWM DS8576-00 April 2011 ISET www.richtek.com 5 RT8576 Absolute Maximum Ratings z z z z z z z z z (Note 1) Supply Voltage, VIN , STATE -------------------------------------------------------------------------------------------- 33V LED1 to LED8 --------------------------------------------------------------------------------------------------------------- 50V PWM, EN, EXT, CS, SS, COMP, OSC, VCCA, OVS, ISET ----------------------------------------------------- 5.5V Power Dissipation, PD @ TA = 25°C TSSOP-24 (Exposed Pad) ----------------------------------------------------------------------------------------------- 2.500W SOP-24 ----------------------------------------------------------------------------------------------------------------------- 1.111W Package Thermal Resistance (Note 2) TSSOP-24 (Exposed Pad), θJA ----------------------------------------------------------------------------------------- 40°C/W TSSOP-24 (Exposed Pad), θJC ---------------------------------------------------------------------------------------- 7°C/W SOP-24 , θJA ------------------------------------------------------------------------------------------------------------------------------------------------------------------ 90°C/W Junction Temperature ------------------------------------------------------------------------------------------------------ 150°C Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------- 260°C Storage Temperature Range --------------------------------------------------------------------------------------------- −65°C to 150°C ESD Susceptibility (Note 3) HBM (Human Body Mode) ----------------------------------------------------------------------------------------------- 2kV MM (Machine Mode) ------------------------------------------------------------------------------------------------------- 200V Recommended Operating Conditions z z z z (Note 4) Supply Voltage, VIN -------------------------------------------------------------------------------------------------------LED1 to LED8 --------------------------------------------------------------------------------------------------------------Junction Temperature Range --------------------------------------------------------------------------------------------Ambient Temperature Range --------------------------------------------------------------------------------------------- 9V to 28V 45V −40°C to 125°C −40°C to 85°C Electrical Characteristics (VIN = 12V, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Supply Voltage Supply Current I VIN Switching Off -- 5 -- mA Shutdown Current I SHDN VEN < 0.7V -- -- 10 μA VDD LDO Output VCCA -- 5 -- V VDD LDO Capability I VCCA 30 -- -- mA VIN UVLO Threshold VUVLO VIN Rising -- -- 8 Hysteresis -- 1.4 -- Logic-High EN Input Threshold Voltage Logic-Low VENH 1.5 -- -- VENL -- -- 0.8 114 120 126 mA -- 1.5 3 % -- 0.6 -- V V V LED Current Programming LED Current Accuracy RISET = 4.53kΩ, VPWM > 1.2V RISET = 4.53kΩ, VPWM > 1.2V LED Current Matching I(MAX) − I(MIN) 2 × I(Avg) LED1 to LED8 Regulation Voltage × 100% I LED = 120mA To be continued www.richtek.com 6 DS8576-00 April 2011 RT8576 Parameter Symbol VLED Threshold Test Conditions No Connection ISET Pin Voltage Min Typ Max Unit -- 0.1 -- V -- 1.2 -- V Dimming Logic-High VPWMH 1.2 -- -- Logic-Low VPWML -- -- 0.4 ROSC = 24kΩ -- 1 -- MHz ROSC = Open -- 100 -- kHz -- 100 -- ns 80 -- -0.5 --- % V Gate Driver Source -- 2.5 -- A Gate Driver Sink -- 3 -- A PWM Input Threshold Voltage V PWM Boost Controller Switching Frequency fOSC Minimum On Time tON Maximum Duty Cycle CS Current Sense Limit Dmax Input Current Limit OVP, UVP, SCP, OTP and Soft-Start OVP Threshold VOVP 1.1 1.2 1.3 V UVP Threshold VUVP 0.57 0.6 0.63 V SCP Threshold VSCP LED1 to LED8 -- 4.3 -- V Soft-Start Current ISS VSS < 2.5V -- 6 -- μA Thermal Shutdown Temperature TSD Lockout Temperature Point -- 150 -- °C Thermal Shutdown Hysteresis ΔTSD Resume Temperature Point -- 20 -- °C STATE Low Voltage VSTATE Open Drain at 10mA -- -- 0.5 V Note 1. Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device. These are for stress ratings. 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 remain possibility to affect device reliability. Note 2. For TSSOP-24 (Exposed Pad), θJA is measured in natural convection at TA = 25°C on a high-effective thermal conductivity test board of JEDEC 51-7 thermal measurement standard. For SOP-24 θJA is measured in natural convection at TA = 25°C on a low-effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard. The measurement case position of θJC is on the exposed pad of the package. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. DS8576-00 April 2011 www.richtek.com 7 RT8576 Typical Operating Characteristics LED Current vs. Input Voltage 100 LED Current vs. PWM Duty Cycle 60 96 LEDs 50 LED Current (mA) 80 LED Current (mA) 96 LEDs 60 LED1 LED2 LED3 LED4 LED5 LED6 LED7 LED8 40 20 PWM = 200Hz PWM = 1kHz PWM = 10kHz 40 30 20 10 VIN = 12V, RISET = 9.1kΩ RISET = 9.1kΩ 0 0 8 10 12 14 16 18 20 22 24 26 0 28 20 30 40 50 60 70 80 90 100 Duty Cycle (%) Input voltage (V) Power On from VIN Efficiency vs. Input Voltage 100 10 96 LEDs Efficiency (%) 95 90 VIN (5V/Div) 85 DRV (5V/Div) 80 75 RISET = 9.1kΩ I IN (1A/Div) VIN = 12V, CSS = 0.1μF 70 8 10 12 14 16 18 20 22 24 26 Time (10ms/Div) 28 Input voltage (V) Power On from PWM Power On from VEN PWM (2V/Div) VEN (2V/Div) DRV (5V/Div) DRV (5V/Div) I IN (1A/Div) VIN = 12V, CSS = 0.1μF Time (10ms/Div) www.richtek.com 8 I IN (1A/Div) VIN = 12V, CSS = 0.1μF Time (10ms/Div) DS8576-00 April 2011 RT8576 Application information The RT8576 is an 8-CH driver controller that delivers well matched LED current to each channel of LED strings. The external N-MOSFET current source will accommodate the power dissipation difference among channels resulting from the forward voltage difference between the LED strings. With high speed current source N-MOSFET drivers, the RT8576 features highly accurate current matching, while also providing very fast turn-on and turn-off times. This allows a very narrow minimum on or off pulse. The RT8576 integrates adjustable switching frequency and soft-start and provides circuitry for over temperature, over voltage, under voltage and current limit protection. Soft-Start The RT8576 employs a soft-start feature to limit the inrush current. The soft-start circuit prevents excessive inrush current and input voltage droop. The soft-start time is determined by a capacitor, CSS, connected between SS and GND and charged with a 6μA constant current as shown in the following equation. tSS (max) = CSS x 4 x 105 (s) The value of capacitor CSS is user-defined to satisfy the designer' requirement. Compensation The regulator loop can be compensated by adjusting the external components connected to the COMP pin. The COMP pin is the output of the internal error amplifier. The compensation capacitor will adjust the zero to maintain stability and the resistor value will adjust the compensator gain for fast transient response. Typical values of the compensation components are RC = 560Ω, CC = 0.22μF. LED Connection The RT8576 equips 8-CH LED drivers and each channel supports up to 15 LEDs. The LED strings are connected from the output of the boost converter to pin OUTx (x = 1 to 8) respectively. If one of the LED channel is not in use, the OUTx pin should be opened directly. Setting and Regulation of LED current The LED current can be calculated by the following equation : 543.6 RISET where RISET is the resistor between the ISET pin and GND. This setting is the reference for the LED current at pin OUTx and represents the sensed LED current for each string. The DC/DC converter regulates the LED current according to the setting. ILED ≅ Over Voltage and Under Voltage Protection The RT8576 integrates Over Voltage Protection (OVP) and Under Voltage Protection (UVP). When the voltage at the OVS pin rises above the threshold voltage of approximately 1.2V or falls below the threshold voltage of approximately 0.6V, the internal switch will be turned off and the STATE pin will be pulled high. The internal switch will be turned on again once the voltage at the OVS pin returns to normal range. The output voltage can be clamped at a certain voltage level and can be calculated by the following equations : ⎛ ⎞ R VOUT(OVP) = VOVP × ⎜ 1 + OVP2 ⎟ ROVP1 ⎠ ⎝ ⎛ ⎞ R VOUT(UVP) = VUVP × ⎜ 1 + OVP2 ⎟ ROVP1 ⎠ ⎝ where ROVP1 and ROVP2 are the resistors in the resistive voltage divider connected to the OVS pin. If at least one string is in normal operation, the controller will automatically ignore the open strings and continue to regulate the current for the strings in normal operation. Suggested value for ROVP2 is up to 3MΩ to prevent loading effect. LED Short Circuit Protection The RT8576 integrates LED Short Circuit Protection (SCP). If one of the OUT1 to OUT8 pin voltages exceeds a threshold of approximately 4.3V during normal operation, the STATE pin will be pulled high for a fault signal. STATE After the IC is enabled. STATE will output logic high if LED short/OVP/UVP/OTP conditions exist. STATE will be reset after VIN or EN is re-applied. DS8576-00 April 2011 www.richtek.com 9 RT8576 Setting the Switching Frequency The RT8576 switching frequency is programmable from 100kHz to 1MHz by adjusting the oscillator resistor, ROSC. The switching frequency can be calculated by the following equation : 21.6 × 109 fSW ≅ 100k + ROSC Current Limit Protection 2 L= D × (1 − D ) × VOUT 2 × f × IOUT The duty cycle can be calculated as the following equation : D= VOUT − VIN VOUT where VOUT is the maximum output voltage, VIN is the minimum input voltage, f is the operating frequency, and The RT8576 can sense the RSENSE voltage between the CS pin and GND to achieve over current protection. The boost converter senses the inductor current during the on period. The duty cycle depends on the current signal and internal slope compensation compared with the error signal. The external switch will be turned off when the current signal is larger than the internal slope compensation. In the off period, the inductor current will decrease until the internal switch is turned on by the oscillator. The current limit value can be calculated by the following equation : 0.5V Current Limit (A) ≅ RSENSE IOUT is the sum of current from all LED strings. Brightness Control Diode Selection The RT8576 features a digital dimming control scheme. A very high contrast ratio true digital PWM dimming is achieved by driving the PWM pin with a PWM signal. The recommended PWM frequency is 200Hz to 10kHz, but the LED current cannot be 100% proportional to duty cycle, especially for high frequency and low duty ratio. Schottky diodes are recommended for most applications because of their fast recovery time and low forward voltage. Power dissipation, reverse voltage rating, and pulsating peak current are important parameters for consideration when making a Schottky diode selection. Make sure that the diode's peak current rating exceeds IPEAK and reverse voltage rating exceeds the maximum output voltage. The boost converter operates in DCM over the entire input voltage range when the inductor value is less than this value, L. With an inductance greater than L, the converter operates in CCM at the minimum input voltage and may be discontinuous at higher voltages. The inductor must be selected with a saturated current rating that is greater than the peak current as provided by the following equation : IPEAK = VOUT × IIOUT VIN × D × T + η × VIN 2×L where η is the efficiency of the power converter. Over Temperature Protection The RT8576 has over temperature protection function to prevent the IC from overheating due to excessive power dissipation. The IC will shut down and the STATE pin will be pulled high when junction temperature exceeds 150°C. Main converter starts switching after junction temperature cools down by approximately 20°C. Capacitor Selection Inductor Selection It is recommended to choose a ceramic capacitor based on the output voltage ripple requirements. The minimum value of the output capacitor, COUT, can be calculated by the following equation : The value of the inductance, L, can be approximated by the following equation, where the transition is from Discontinuous Conduction Mode (DCM) to Continuous Conduction Mode (CCM) : www.richtek.com 10 The input capacitor reduces current spikes from the input supply and minimizes noise injection to the converter. For general applications, six to eight 4.7μF ceramic capacitors are sufficient. A value higher or lower may be used depending on the noise level from the input supply and the input current to the converter. COUT = IOUT × D ΔVOUT × f DS8576-00 April 2011 RT8576 Maximum Power Dissipation (W)1 where ΔVOUT is the peak-to-peak ripple voltage at the output. Thermal Considerations For continuous operation, do not exceed absolute maximum junction temperature. The maximum power dissipation depends on the thermal resistance of the IC package, PCB layout, rate of surrounding airflow, and difference between junction and ambient temperature. The maximum power dissipation can be calculated by the following formula : PD(MAX) = (TJ (MAX) − TA) / θJA where TJ (MAX) is the maximum junction temperature, TA is the ambient temperature, and θJA is the junction to ambient thermal resistance. For recommended operating condition specifications of the RT8576, the maximum junction temperature is 125°C and TA is the ambient temperature. The junction to ambient thermal resistance, θJA, is layout dependent. For TSSOP24 (Exposed Pad) packages, the thermal resistance, θJA, is 40° C/W on a standard JEDEC 51-7 four-layer thermal test board. For SOP-24 packages, the thermal resistance, θJA , is 90°C/W on a standard JEDEC 51-3 single-layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formula : 1.0 0.8 SOP-24 0.6 0.4 0.2 0.0 25 50 75 100 125 Figure 3. Derating Curve for RT8576 Packages Layout Considerations Careful PCB layout is very important for designing switching power converter circuits. The following layout guidelines should be strictly followed for best performance of the RT8576. ` The power components L1, D1, CIN, COUT must be placed as close as possible to the IC to reduce current loop. The PCB trace between power components must be as short and wide as possible. ` The compensation circuit should be kept away from the power loops and shielded with a ground trace to prevent any noise coupling. Place the compensation components, RC and CC, as close as possible to pin 22. ` The exposed pad of the chip should be connected to ground plane for thermal consideration. PD(MAX) = (125°C − 25°C) / (90°C/W) = 1.111W for DS8576-00 April 2011 1.4 1.2 Ambient Temperature (°C) TSSOP-24 (Exposed Pad) package The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. For the RT8576 packages, the derating curves in Figure 3 allow the designer to see the effect of rising ambient temperature on the maximum power dissipation. TSSOP-24 (Exposed Pad) 1.8 1.6 0 PD(MAX) = (125°C − 25°C) / (40°C/W) = 2.500W for SOP-24 package 2.6 2.4 2.2 2.0 www.richtek.com 11 RT8576 The compensation circuit should be kept away from the power loops and shielded with a ground trace to prevent any noise coupling. PWM OUT1 OUT2 OUT3 OUT4 GND OUT6 OUT7 OUT8 OUT5 OVS ISET 24 2 23 3 22 4 21 5 20 GND 6 7 19 18 8 17 9 16 10 11 15 25 14 12 13 Locate the CVIN as close to VIN STATE CC2 as possible. NC COMP RC CC1 COUT NC SS VOUT VIN PGND CVIN D1 VIN VCCA L1 EXT CS REXT EN Msw C IN OSC RF RSENSE CF RGND PGND GND Place the power components as close to the IC As possible. The traces should be wide and short especially for the high current loop. Figure 4. TSSOP-24 (Exposed Pad) PCB Layout Guide The compensation circuit should be kept away from the power loops and shielded with a ground trace to prevent any noise coupling. PWM OUT1 OUT2 OUT3 OUT4 GND OUT8 OUT6 OUT7 OVS ISET OSC 24 2 23 3 22 4 21 5 20 6 19 7 18 8 17 9 16 10 15 11 14 12 13 STATE NC COMP NC SS VIN PGND VCCA EXT OUT5 CS EN CC2 GND Locate the CVIN as close to VIN as possible. RC CC1 COUT VOUT CVIN L1 VIN REXT Msw CIN RF RGND D1 CF RSENSE GND PGND Place the power components as close to the IC As possible. The traces should be wide and short especially for the high current loop. Figure 5. SOP-24 PCB Layout Guide www.richtek.com 12 DS8576-00 April 2011 RT8576 Outline Dimension Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 1.000 1.200 0.039 0.047 A1 0.000 0.150 0.000 0.006 A2 0.800 1.050 0.031 0.041 b 0.190 0.300 0.007 0.012 D 7.700 7.900 0.303 0.311 e 0.65 0.026 E 6.300 6.500 0.248 0.256 E1 4.300 4.500 0.169 0.177 L 0.450 0.750 0.018 0.030 U 3.700 4.900 0.146 0.193 V 2.200 3.100 0.087 0.122 24-Lead TSSOP (Exposed Pad) Plastic Package DS8576-00 April 2011 www.richtek.com 13 RT8576 H A M B J F C I D Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 15.189 15.596 0.598 0.614 B 7.391 7.595 0.291 0.299 C 2.362 2.642 0.093 0.104 D 0.330 0.508 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.229 0.330 0.009 0.013 I 0.102 0.305 0.004 0.012 J 10.008 10.643 0.394 0.419 M 0.381 1.270 0.015 0.050 24–Lead SOP Plastic Package Richtek Technology Corporation Richtek Technology Corporation Headquarter Taipei Office (Marketing) 5F, No. 20, Taiyuen Street, Chupei City 5F, No. 95, Minchiuan Road, Hsintien City Hsinchu, Taiwan, R.O.C. Taipei County, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Tel: (8862)86672399 Fax: (8862)86672377 Email: [email protected] Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek. www.richtek.com 14 DS8576-00 April 2011