RT8565 Small Package, High Performance, Diode Embedded, Asynchronous Boost, 6 WLEDs Driver General Description Features The RT8565 is a high efficiency LED driver IC capable of driving 6 LEDs. The RT8565 integrates 26V/0.9A power switch with an internal Schottky diode. z The RT8565 is a current mode boost converter which is fixed at 600kHz operating frequency and has a wide input voltage range from 2.8V to 4.5V. z z z z z z During brightness dimming, the RT8565 does not burst the LED current. Therefore, no audible noises are generated on the output capacitor. The RT8565 also has internal over voltage protection setting to prevent the output from exceeding the absolute maximum ratings during open LED conditions. z z Applications z z GPS, Portable DVD Backlight Mobile Phone, Smart Phone Pin Configurations (TOP VIEW) NC The LED current is set with an external resistor and the feedback voltage is regulated to 200mV. During operation, an internal 6-bit DAC is used for brightness control. Users can easily configure up to 64 steps of LED current via the EN pin. Internal Schottky Diode Internal Soft-Start and Compensation 200mV Reference Voltage 64-Step Pulse Dimming Open LED Protection Internally Set Over Voltage Protection Over Temperature Protedtion Current Limit Protection RoHS Compliant and Halogen Free 8 The RT8565 is available in a small WQFN-8L 1.6x1.6 package. FB 1 7 VIN VOUT 2 6 EN GND 3 5 LX 4 NC Ordering Information RT8565 Package Type QW : WQFN-8L 1.6x1.6 (COL) (W-Type) Lead Plating System G : Green (Halogen Free and Pb Free) Note : WQFN-8L 1.6x1.6 (COL) Marking Information C0 : Product Code C0W W : Date Code Richtek products are : ` RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. ` Suitable for use in SnPb or Pb-free soldering processes. DS8565-01 April 2011 www.richtek.com 1 RT8565 Typical Application Circuit VOUT 2 L 10µH VIN 2.8V to 4.5V CIN 1µF COUT 1µF 5 LX RT8565 : : 6 LEDs : : 7 VIN FB 6 EN Chip Enable 1 RSET GND 3 Timing Diagram 1ms < tIH 0 0.5µs < tIH 1 100% 2 63/64 0.5µ < tIH < 500µs 3 4 5 4ms < tSHDN 62 63 0 1 100% 62/64 61/64 63/64 60/64 2/64 1/64 Functional Pin Description Pin No. Pin Name Pin Function 1 FB Feedback Voltage Input. Connect a resistor from this pin to GND to set the LED current. 2 VOUT Boost Converter Output. 3 GND Ground. 4, 8 NC No Internal Connection. 5 LX Switch Node of Boost Converter. 6 EN Chip Enable (Active High). 7 VIN Power Supply Input. www.richtek.com 2 DS8565-01 April 2011 RT8565 Function Block Diagram VOUT OVP OTP Soft-Start LX OCP VIN PWM Control UVLO OSC Shutdown Delay + + - EN EN Control Dimming + - Soft-Start VREF OCP Error AMP Internal Compensation GND OTP FB DS8565-01 April 2011 www.richtek.com 3 RT8565 Absolute Maximum Ratings z z z z z z z z (Note 1) Supply Input Voltage, VIN to GND ------------------------------------------------------------------------------------- −0.3V to 5.4V EN, FB to GND ------------------------------------------------------------------------------------------------------------ −0.3V to 5.4V LX, VOUT to GND --------------------------------------------------------------------------------------------------------- −0.3V to 40V Power Dissipation, PD @ TA = 25°C WQFN−8L 1.6x1.6 (COL) -----------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) WQFN−8L 1.6x1.6 (COL), θJA -----------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------- Recommended Operating Conditions z z z 0.833W 120°C/W 260°C 150°C −65°C to 150°C (Note 3) Supply Input Voltage ------------------------------------------------------------------------------------------------------ 2.8V to 4.5V Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 3.6V, TA = 25°C, unless otherwise specified) Parameter Under Voltage Lockout Threshold Symbol VUVLO Test Conditions VIN Rising Under Voltage Lockout Hysteresis ΔV UVLO Min Typ Max Unit 2 2.2 2.45 V -- 0.1 -- V IVCC FB = 1.5V, Not Switching -- 850 -- μA IVCC_SW FB = 0V, Switching -- -- 3 mA ISHDN VIN = 4V, VEN ≤ 0.8V -- 1 4 μA VIH VIL 1.5 -- --- -0.4 V IIH 1 -- 10 μA Logic-Low tIL 0.5 -- 500 Logic-High tIH 0.5 -- -- tSHDN 4 -- -- ms Switching Frequency fOSC −20% 0.6 20% MHz LX On-Resistance (N-MOSFET) RDS(ON) -- 0.5 0.7 Ω Minimum ON Time tON -- 100 -- ns Maximum Duty DMAX -- 92 -- % Feedback Reference Voltage VREF −5% 200 5% mV VIN Quiescent Current VIN Shutdown Current Control Input EN Threshold Voltage Logic-High Logic-Low EN Sink Current EN Dimming Time Shutdown Delay Time μs Boost Converter Fault Protection LX Current Limit ILIM -- 0.9 -- A Over Voltage Protection V OVP -- 26 -- V Thermal Shutdown Temperature Thermal Shutdown Hysteresis T SD -- 160 -- °C ΔTSD -- 30 -- °C www.richtek.com 4 DS8565-01 April 2011 RT8565 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. θJA is measured in the natural convection at TA = 25°C on a high effective thermal conductivity four-layer test board of JEDEC 51-7 thermal measurement standard. Note 3. The device is not guaranteed to function outside its operating conditions. DS8565-01 April 2011 www.richtek.com 5 RT8565 Typical Operating Characteristics Quiescent Current vs. Input Voltage 1800 1050 1700 Quiescent Current (μA) Quiescent Current (μA) Quiescent Current vs. Input Voltage 1100 1000 950 900 850 800 750 700 1600 1500 1400 1300 1200 1100 650 No Switching 600 2.8 3.1 3.4 3.7 4.0 4.3 Switching 1000 2.8 4.6 3.1 3.4 4.0 4.3 4.6 Input Voltage (V) Input Voltage (V) OVP vs. Input Voltage Feedback Voltage vs. Temperature 199.5 25.9 199.3 Feedback Voltage (V) 26.0 25.8 OVP (V) 3.7 25.7 25.6 199.1 198.9 198.7 25.5 198.5 25.4 198.3 VIN = 3.7V 2.8 3.1 3.4 3.7 4.0 4.3 4.6 -50 -25 0 25 50 75 100 Input Voltage (V) Temperature (°C) Power Off Pulse Dimming for LED Current 125 VEN (2V/Div) VEN (2V/Div) VFB (200mV/Div) I LED (10mA/Div) VIN = 3.7V, 6 WLEDs with 20mA Time (500μs/Div) www.richtek.com 6 I LED (5mA/Div) VIN = 3.7V, 6 WLEDs with 20mA Time (10ms/Div) DS8565-01 April 2011 RT8565 Soft-Start Line Transient Response VEN (5V/Div) VIN 4.2 (V) 3.2 VLX (10V/Div) I LED (10mA/Div) I LED (10mA/Div) VIN = 3.7V, 6 WLEDs with 20mA VIN = 3.2V to 4.2V, 6 WLEDs with 20mA Time (1ms/Div) Time (1ms/Div) Efficiency vs. Load Current 90 80 80 70 VIN = 4.2V VIN = 3.7V VIN = 3V 60 Load = 10mA Load = 20mA Load = 30mA 70 Efficiency (%) Efficiency (%) Efficiency vs. Input Voltage 90 50 40 30 20 60 50 40 30 20 10 VOUT = 20V, L = 10μH 0 10 VOUT = 20V, L = 10μH 0 0 5 10 15 20 Load Current (mA) DS8565-01 April 2011 25 30 2.8 3.1 3.4 3.7 4 4.3 4.6 4.9 Input Voltage (V) www.richtek.com 7 RT8565 Application Information Soft-Start The function of Soft-Start is to avoid high inrush current during start-up LED Current the major concerns for portable devices, such as for mobile phone. The inductor should have low core loss at 600kHz and low DCR for better efficiency. The inductor saturation current rating should be able to cover the inductor peak current. The loop control of the boost converter keeps VFB equal to a reference voltage VREF. Therefore, when RSET is connected between the FB pin and GND, the LED current will be determined by the current through RSET, which is equal to VFB / RSET. Brightness Dimming The RT8565 implements a pulse dimming method to control the brightness of the white LEDs. Users can easily configure the LED current with a serial pulse. The dimming of white LED current can be achieved by applying a pulse signal to the EN pin. There are a total of 64 steps of current levels that can be set by users. The detail operation of the brightness dimming is shown in Timing Diagram. Current Limiting The current flowing through the inductor during the charging period is detected by a current sensing circuit. If the value over the current limit, the N-MOSFET will be turned off. The inductor will then be forced to leave charging stage and enter discharging stage. Therefore, the inductor current will not increase over the current limit. Shutdown Delay When the EN voltage is in logic-low for 4ms typical during for pulse dimming, the system will enter shutdown. OVP/UVLO/OTP When the output voltage is higher than a specified value or input voltage is lower than a specified value, the IC will enter protection mode to prevent abnormal operation. If the die temperature > 160°C, the IC will also enter protection mode. The power MOSFET will be turned off during protection mode to prevent abnormal operation. Inductor Selection The recommended Inductor value for 6-WLED applications is from 10μH to 22μH. Small size and better efficiency are www.richtek.com 8 Capacitor Selection Input ceramic capacitor of 1μF and output ceramic capacitor of 1μF are recommended for driving 6-WLED applications. For better voltage filtering, ceramic capacitors with low ESR are recommended. X5R and X7R types are suitable because of their wide voltage and temperature ranges. 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 RT8565, the maximum junction temperature is 125°C and TA is the ambient temperature. The junction to ambient thermal resistance, θ JA , is layout dependent. For WQFN-8L 1.6x1.6 packages, the thermal resistance, θJA, is 120°C/W on a standard JEDEC 51-7 four-layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formula : PD(MAX) = (125°C − 25°C) / (120°C/W) = 0.833W for WQFN-8L 1.6x1.6 package The maximum power dissipation depends on operating ambient temperature for fixed T J(MAX) and thermal resistance. For the RT8565 package, the derating curve in Figure 1 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. DS8565-01 April 2011 RT8565 0.75 The inductor should be placed as close as possible to the switch pin to minimize the noise coupling into other circuits. The LX node copper area should be minimized for reducing EMI. NC Four-Layer PCB COUT should be connected directly from Pin 2 to ground rather than across the LEDs 8 FB 1 7 VIN VOUT 2 6 EN GND 3 5 LX COUT 0.50 Battery L CIN 4 CIN should be placed as close as possible to the VIN pin for good filtering. NC Maximum Power Dissipation (W) 1.00 0.25 GND RSET 0.00 0 25 50 75 100 125 Ambient Temperature (°C) Figure 1. Derating Curve for the RT8565 Package FB node copper area should be minimized and kept far away from noise sources (LX pin) and RSET should be placed as close as possible to the FB pin. Figure 2. PCB Layout Guide Layout Consideration For best performance of the RT8565, the following guidelines must be strictly followed : ` Input and output capacitors should be placed close to the IC and connected to the ground plane to reduce noise coupling. ` GND and Exposed Pad should be connected to a strong ground plane for heat sinking and noise protection. ` Keep the main current traces as short and wide as possible. ` LX node of DC/DC converter experiences high frequency voltage swings. It should be kept in a small area. ` Place the feedback components as close as possible to the IC and away from the noisy devices. DS8565-01 April 2011 www.richtek.com 9 RT8565 Outline Dimension Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.700 0.800 0.028 0.031 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.150 0.250 0.006 0.010 D 1.550 1.650 0.061 0.065 E 1.550 1.650 0.061 0.065 e L 0.400 0.350 0.016 0.450 0.014 0.018 W-Type 8L QFN 1.6x1.6 (COL) 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 10 DS8565-01 April 2011