® RT8073 6A, 2MHz, High Efficiency Synchronous Step-Down Converter General Description Features The RT8073 is a high efficiency PWM step-down converter and capable of delivering 6A output current over a wide input voltage range from 2.9V to 5.5V. z z z z The RT8073 provides accurate regulation for a variety of loads with an ±1% reference voltage at room temperature. For reducing inductor size, it provides up to 2MHz switching frequency. The efficiency is maximized through the integrated 50mΩ for high side, 35mΩ for low side MOSFETs and 250μA typical supply current. z z z z z z The RT8073 features over current protection, frequency fold back function in shorted circuit, hiccup mode under voltage protection and over temperature protection. z z z The RT8073 is available in SOP-8 (Exposed Pad) and WDFN-12L 3x3 packages. Ω MOSFETs Integrated 50mΩ Ω and 35mΩ 6A Output Current High Efficiency Up to 95% 2.9V to 5.5V Input Range Adjustable PWM Frequency : 300kHz to 2MHz 0.8V ±1% Reference Voltage Adjustable External Soft-Start Power Good Indicator (WDFN-12L 3x3 only) Over Current Protection Under Voltage Protection Over Temperature Protection SOP-8 (Exposed Pad) and 12-Lead WDFN Packages RoHS Compliant and Halogen Free Applications z Ordering Information z RT8073 z Package Type SP : SOP-8 (Exposed Pad-Option 2) QW : WDFN-12L 3x3 (W-Type) Low Voltage, High Density Power Systems Distributed Power Systems Point-of-Load Conversions Marking Information RT8073GSP RT8073GSP : Product Number Lead Plating System G : Green (Halogen Free and Pb Free) RT8073 GSPYMDNN Note : YMDNN : Date Code Richtek products are : ` RT8073GQW RoHS compliant and compatible with the current require- 5C= : Product Code ments of IPC/JEDEC J-STD-020. ` YMDNN : Date Code 5C=YM DNN Suitable for use in SnPb or Pb-free soldering processes. Simplified Application Circuit VIN VIN BOOT RT8073 CIN CBOOT L LX EN RC CC RT RT November 2012 RFB1 FB GND Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS8073-01 VOUT COUT COMP RFB2 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT8073 Pin Configurations COMP GND 2 EN 3 VIN 4 PGND 8 FB 7 RT 6 LX 5 BOOT 9 COMP PGOOD SS EN VIN VIN SOP-8 (Exposed Pad) 1 2 3 4 5 6 PGND (TOP VIEW) 13 12 11 10 9 8 7 FB RT LX LX LX BOOT WDFN-12L 3x3 Functional Pin Description Pin No. Pin Function Pin Name SOP-8 (Exposed Pad) WDFN-12L 3x3 1 1 COMP Compensation Node. 2 -- GND Analog Ground. 3 4 EN Chip Enable. Externally pulled high to enable and pulled low to disable this chip, and it is internally pulled up to high when the pin is floating. 4 5, 6 VIN Power Input. 5 7 BOOT Bootstrap Supply for High Side Gate Driver. 6 8, 9, 10 LX Switch Node. 7 11 RT Frequency Setting. 8 12 FB Feedback Voltage Input. 9 13 (Exposed Pad) PGND Power Ground. The exposed pad must be shouldered to a large PCB and connected to PGND for maximum power dissipation. -- 2 PGOOD Power Good Indicator with Open Drain Output. It is high impedance when the output voltage is regulated. It is internally pulled low when the chip is shutdown, thermal shutdown or VIN is under UVLO threshold. -- 3 SS Soft-Start Control. Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS8073-01 November 2012 RT8073 Function Block Diagram For SOP-8 (Exposed Pad) Package VIN VIN Over Temperature Protection Internal pull up current EN EN Threshold UVLO Shutdown Control Current Sense GND BOOT RT Oscillator Control Logic Slope Compensation Soft-Start Driver LX PWM Comparator Voltage Reference Error Amplifier FB PGND COMP For WDFN-12L 3x3 Package VIN VIN Internal pull up current EN EN Threshold RT UVLO Shutdown Control Current Sense BOOT Oscillator VIN SoftStart SS Over Temperature Protection Voltage Reference Control Logic Slope Compensation Driver LX PWM Comparator Error Amplifier PGND FB PGOOD Power Good Threshold COMP Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS8073-01 November 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8073 Operation The RT8073 is a current mode synchronous step-down DC/DC converter with two integrated power MOSFETs. It can deliver up to 6A output current from a 2.9V to 5.5V input supply. The RT8073's current mode architecture allows the transient response to be optimized over a wide input voltage and load range. Cycle-by-cycle current limit provides protection against shorted outputs and soft-start eliminates input current surge during start-up. PGOOD Comparator When the feedback voltage (VFB) rises above 94% or falls below 106% of reference voltage, the PGOOD open drain output will be high impedance. The PGOOD open drain output will be internally pulled low when the feedback voltage (VFB) falls below 90% or rises above 110% of reference voltage. Soft-Start (SS) Error Amplifier The error amplifier adjusts COMP voltage by comparing the feedback signal (VFB) from the output voltage with the internal 0.8V reference. When the load current increases, it causes a drop in the feedback voltage relative to the reference, the COMP voltage then rises to allow higher inductor current to match the load current. Oscillator (OSC) The frequency of the oscillator is adjustable by an external resistor connected between the RT pin and GND. The available switching frequency range is from 300kHz to 2MHz. Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 An internal current source charges an external capacitor to build the soft-start ramp voltage (VSS). The VFB voltage will track the VSS during soft-start interval. The chip will use internal soft-start if the SS pin is floating. The nominal internal soft-start time is 800μs. Over Temperature Protection (OTP) The RT8073 implements an internal over temperature protection. When junction temperature is higher than 165°C, it will stop switching operation. Once the junction temperature decreases below 145°C, the RT8073 will automatically resume switching. is a registered trademark of Richtek Technology Corporation. DS8073-01 November 2012 RT8073 Absolute Maximum Ratings z z z z z z z z z (Note 1) Supply Input Voltage, VIN ----------------------------------------------------------------------------------------BOOT to LX ----------------------------------------------------------------------------------------------------------Other Pins ------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------WDFN-12L 3x3 ------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) SOP-8 (Exposed Pad), θJA ---------------------------------------------------------------------------------------SOP-8 (Exposed Pad), θJC --------------------------------------------------------------------------------------WDFN-12L 3x3, θJA ------------------------------------------------------------------------------------------------WDFN-12L 3x3, θJC ------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Model) ---------------------------------------------------------------------------------------- Recommended Operating Conditions z z z −0.3V to 6.5V −0.3V to 6V −0.3V to (VIN + 0.3V) 2.041W 1.667W 49°C/W 15°C/W 60°C/W 7.5°C/W 260°C 150°C −65°C to 150°C 2kV (Note 4) Supply Input Voltage, VIN ----------------------------------------------------------------------------------------- 2.9V to 5.5V Junction Temperature Range -------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 5V, CIN = 10μF, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Input Power Supply Under Voltage Lockout Threshold VUVLO VIN Rising -- 2.6 2.8 V Quiescent Current IQ Active, VFB = 0.9V, Not switching -- 250 -- μA Shutdown Current ISHDN -- 2 5 μA VREF 0.792 0.8 0.808 V Voltage Reference Voltage Reference Enable Logic-High VIH 1.5 -- 5.5 Logic-Low VIL -- -- 0.4 300 -- 2000 RT = 28.7kΩ -- 1400 -- RT pin is floating -- 300 -- Minimum On-Time -- 80 -- ns Minimum Off-Time -- 60 -- ns EN Input Voltage V Switching Frequency Setting Switching Frequency fOSC Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS8073-01 November 2012 kHz is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT8073 Parameter Symbol Test Conditions Min Typ Max Unit MOSFET High Side MOSFET On-resistance VIN = 5V, BOOT − LX = 5V -- 50 -- mΩ Low Side MOSFET On-resistance VIN = 5V -- 35 -- mΩ 7 9 -- A VFB Rising (Good) -- 94 -- VFB Falling (Fault) -- 90 -- VFB Rising (Fault) -- 110 -- VFB Falling (Good) -- 106 -- Rising -- 165 -- °C -- 20 -- °C Current Limit Current Limit Threshold Power Good Power Good Range (WDFN-12L 3x3 only) % VREF Over Temperature Protection Thermal Shutdown Thermal Shutdown Hysteresis Note 1. Stresses beyond those listed “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 may affect device reliability. Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is measured at 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. Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS8073-01 November 2012 RT8073 Typical Application Circuit VIN VIN CIN1 10µF BOOT CBOOT 0.1µF RT8073 CIN2 10µF RPG 100k LX PGOOD Chip Enable VOUT L COUT1 10µF EN PGND SS RT CSS 10nF R T 28.7k RFB1 COUT3 47µF to 100µF GND COMP CHF* COUT2 10µF RC FB CC RFB2 * : Option Table 1. Recommended Component Selection VOUT (V) RFB (kΩ) RFB2 (kΩ) R C (kΩ) CC (nF) L (μH) COUT 3.3 75 24 33 0.33 0.47 Cer. 20μF + E-Cap 100μF 2.5 51 24 24 0.47 0.47 Cer. 20μF + E-Cap 100μF 1.8 30 24 18 0.56 0.47 Cer. 20μF + E-Cap 100μF 1.5 21 24 15 0.68 0.33 Cer. 20μF + E-Cap 100μF 1.2 12 24 12 1 0.33 Cer. 20μF + E-Cap 100μF 1 6 24 10 1 0.33 Cer. 20μF + E-Cap 100μF Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS8073-01 November 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT8073 Typical Operating Characteristics Output Voltage vs. Input Voltage 1.20 90 1.18 80 1.16 70 Output Voltage (V) Efficiency (%) Efficiency vs. Load Current 100 VIN = 3.3V VIN = 4V VIN = 5V 60 50 40 30 1.14 1.12 1.10 1.08 1.06 20 1.04 10 1.02 VOUT = 1.1V 0 0.001 VOUT = 1.1V 1.00 0.01 0.1 1 10 2.5 3 3.5 Load Current (A) 4 4.5 5 5.5 Input Voltage (V) Output Voltage vs. Temperature Output Voltage vs. Output Current 1.16 1.18 1.15 1.16 1.14 Output Voltage (V) Output Voltage (V) 1.14 1.13 1.12 1.11 1.10 1.09 1.12 1.10 VIN = 5V VIN = 4V VIN = 3.3V 1.08 1.06 1.08 1.04 1.07 VIN = 5V, VOUT = 1.1V, IOUT = 1.5A VOUT = 1.1V 1.06 1.02 -50 -25 0 25 50 75 100 0.0 125 0.6 1.2 1.8 Temperature (°C) Frequency vs. Input Voltage 3.0 3.6 4.2 4.8 5.4 6.0 Switching Frequency vs. Temperature 1.8 1.8 1.7 1.7 Switching Frequency (MHz)1 Frequency (MHz)1 2.4 Output Current (A) 1.6 1.5 1.4 1.3 1.2 1.1 1.6 1.5 1.4 1.3 1.2 1.1 VOUT = 1.1V, IOUT = 1.3A VOUT = 1.1V, IOUT = 1.3A 1.0 1.0 2.5 3 3.5 4 4.5 5 Input Voltage (V) Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 5.5 -50 -25 0 25 50 75 100 125 Temperature (°C) is a registered trademark of Richtek Technology Corporation. DS8073-01 November 2012 RT8073 Currrent Limit vs. Temperature Currrent Limit vs. Input Voltage 10.0 12.0 11.5 9.5 Currrent Limit (A) Currrent Limit (A) 11.0 10.5 10.0 9.5 9.0 8.5 8.0 9.0 8.5 8.0 7.5 7.5 VOUT = 1.1V VIN = 5V, VOUT = 1.1V 7.0 7.0 -50 -25 0 25 50 75 100 2.5 125 3.5 4 4.5 5 Input Voltage (V) Load Transient Response Load Transient Response VOUT (100mV/Div) VOUT (100mV/Div) IOUT (2A/Div) IOUT (2A/Div) Time (100μs/Div) Time (100μs/Div) Output Ripple Voltage Output Ripple Voltage VOUT (20mV/Div) VOUT (20mV/Div) VLX (5V/Div) VLX (5V/Div) VIN = 5V, VOUT = 1.1V, IOUT = 6A Time (250ns/Div) Copyright © 2012 Richtek Technology Corporation. All rights reserved. November 2012 5.5 VIN = 5V, VOUT = 1.1V, IOUT = 0A to 3A VIN = 5V, VOUT = 1.1V, IOUT = 0A to 6A DS8073-01 3 Temperature (°C) VIN = 5V, VOUT = 3.3V, IOUT = 6A Time (250ns/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT8073 Power On from VIN Power Off from VIN VIN (5V/Div) VIN (5V/Div) VOUT (2V/Div) VOUT (2V/Div) ILX (5A/Div) ILX (5A/Div) VIN = 5V, VOUT = 3.3V, IOUT = 6A VIN = 5V, VOUT = 3.3V, IOUT = 6A Time (1ms/Div) Time (10ms/Div) Power On from EN Power Off from EN VEN (5V/Div) VEN (5V/Div) VOUT (2V/Div) VOUT (2V/Div) ILX (5A/Div) ILX (5A/Div) VIN = 5V, VOUT = 3.3V, IOUT = 6A Time (250μs/Div) Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 VIN = 12V, VOUT = 1.05V, IOUT = 3A Time (10ms/Div) is a registered trademark of Richtek Technology Corporation. DS8073-01 November 2012 RT8073 Application Information The basic RT8073 application circuit is shown in Typical Application Circuit. External component selection is determined by the maximum load current and begins with the selection of the inductor value and operating frequency followed by CIN and COUT. Output Voltage Setting The output voltage is set by an external resistive divider according to the following equation : ⎛ R ⎞ VOUT = VREF × ⎜ 1+ FB1 ⎟ R ⎝ FB2 ⎠ The operating frequency of the RT8073 is determined by an external resistor that is connected between the SHDN/ RT pin and GND. The value of the resistor sets the ramp current that is used to charge and discharge an internal timing capacitor within the oscillator. The RT resistor value can be determined by examining the frequency vs. RT curve. Although frequency as high as 2MHz is possible, the minimum on-time of the RT8073 imposes a minimum limit on the operating duty cycle. The minimum on-time is typically 80ns. Therefore, the minimum duty cycle is equal to 100 x 80ns x f (Hz). where VREF equals to 0.8V (typical) VOUT RFB1 FB RT8073 RFB2 GND Switching Frequency (MHz)1 The resistive divider allows the FB pin to sense a fraction of the output voltage as shown in Figure 1. 3.0 2.5 2.0 1.5 1.0 0.5 Figure 1. Setting the Output Voltage 0.0 Soft-Start (SS) An internal current source charges an external capacitor to build the soft-start ramp voltage (VSS). The VFB voltage will track the VSS during soft-start interval. The chip will use internal soft-start if the SS pin is floating. The nominal internal soft-start time is 800μs. With external soft-start, the typical soft-start time can be calculated as following equation : tSS (ms) = 0.1 x CSS (nF) For example, if CSS = 10nF, the soft-start time is 1ms. 0 20 40 60 80 100 120 140 160 180 200 RT (k Ω) Figure 2 Chip Enable Operation The EN pin is the chip enable input. Pulling the EN pin low (<0.4V) will shut down the device. During shutdown mode, the RT8073 quiescent current drops to lower than 2μA. Driving the EN pin high (>1.5V, 5.5V) will turn on the device again. For external timing control, the EN pin can also be externally pulled high by adding a REN resistor and CEN capacitor from the VIN pin (see Figure 3). Operating Frequency Selection of the operating frequency is a tradeoff between efficiency and component size. High frequency operation allows the use of smaller inductor and capacitor values. Operation at lower frequency improves efficiency by reducing internal gate charge and switching losses but requires larger inductance and/or capacitance to maintain low output ripple voltage. Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS8073-01 November 2012 EN VIN REN CEN EN RT8073 GND Figure 3. Enable Timing Control is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT8073 An external MOSFET can be added to implement digital control on the EN pin when no system voltage above 1.5V is available, as shown in Figure 4. In this case, the pull-up resistor, REN, is connected between VIN and the EN pin. MOSFET Q1 will be under logic control to pull down the EN pin. VIN EN Hiccup Mode VOUT (500mV/Div) REN EN Q1 RT8073 ILX (5A/Div) GND VOUT short to GND Time (1ms/Div) Figure 4. Digital Enable Control Circuit Figure 5. Hiccup Mode Under Voltage Protection Slope Compensation and Inductor Peak Current Slope compensation provides stability in constant frequency architectures by preventing sub-harmonic oscillations at duty cycles greater than 50%. It is accomplished internally by adding a compensating ramp to the inductor current signal. Normally, the maximum inductor peak current is reduced when slope compensation is added. In the RT8073, however, separated inductor current signals are used to monitor over current condition. This keeps the maximum output current relatively constant regardless of duty cycle. Hiccup Mode For the RT8073, it provides Hiccup Mode Under Voltage Protection (UVP). When the output is shorted to ground, the UVP function will be triggered to shut down switching operation. If the under voltage condition remains for a period, the RT8073 will retry automatically. When the under voltage condition is removed, the converter will resume operation. The UVP is disabled during soft-start period. Inductor Selection The inductor value and operating frequency determine the ripple current according to a specific input and output voltage. The ripple current ΔIL increases with higher VIN and decreases with higher inductance. V V ΔIL = ⎡⎢ OUT ⎤⎥ × ⎡⎢1− OUT ⎤⎥ VIN ⎦ ⎣ f ×L ⎦ ⎣ Having a lower ripple current can reduce not only the ESR losses in the output capacitors but also the output voltage ripple. However, it requires a large inductor to achieve this goal. For the ripple current selection, the value of ΔIL = 0.4(IMAX) will be a reasonable starting point. The largest ripple current occurs at the highest VIN. To guarantee that the ripple current stays below the specified maximum, the inductor value should be chosen according to the following equation : ⎡ VOUT ⎤ ⎡ VOUT ⎤ L =⎢ × ⎢1 − ⎥ ⎥ f I V × Δ L(MAX) ⎦ ⎣ IN(MAX) ⎦ ⎣ The inductor's current rating (caused a 40°C temperature rising from 25°C ambient) should be greater than the maximum load current and its saturation current should be greater than the short circuit peak current limit. Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 is a registered trademark of Richtek Technology Corporation. DS8073-01 November 2012 RT8073 2.4 Maximum Power Dissipation (W) 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, the maximum junction temperature is 125°C. The junction to ambient thermal resistance, θJA, is layout dependent. For SOP-8 (Exposed Pad) packages, the thermal resistance, θJA, is 49°C/W on a standard JEDEC 51-7 four-layer thermal test board. For WDFN-12L 3x3 packages, the thermal resistance, θJA, is 60°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 formulas : PD(MAX) = (125°C − 25°C) / (49°C/W) = 2.041W for SOP-8 (Exposed Pad) package Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS8073-01 November 2012 2.0 1.8 1.6 1.4 WDFN-12L 3x3 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 6. Derating Curve of Maximum Power Dissipation Layout Considerations Follow the PCB layout guidelines for optimal performance of RT8073. ` A ground plane is recommended. If a ground plane layer is not used, the signal and power grounds should be segregated with all small-signal components returning to the GND pin at one point that is then connected to the PGND pin close to the IC. The exposed pad should be connected to GND. ` Connect the terminal of the input capacitor(s), CIN, as close as possible to the VIN pin. This capacitor provides the AC current into the internal power MOSFETs. ` LX node is with high frequency voltage swing and should be kept within small area. Keep all sensitive small-signal nodes away from the LX node to prevent stray capacitive noise pick-up. ` Flood all unused areas on all layers with copper. Flooding with copper will reduce the temperature rise of power components. ` Connect the FB pin directly to the feedback resistors. The resistor divider must be connected between VOUT and GND. PD(MAX) = (125°C − 25°C) / (60°C/W) = 1.667W for WDFN-12L 3x3 package The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curves in Figure 6 allow the designer to see the effect of rising ambient temperature on the maximum power dissipation. Four-Layer PCB SOP-8 (Exposed Pad) 2.2 is a registered trademark of Richtek Technology Corporation. www.richtek.com 13 RT8073 Connect the FB pin directly to feedback resistors. The resistor divider must be connected between VOUT and GND. CC GND RC COMP PGOOD GND CSS SS EN REN VIN VIN CIN must be placed between VIN and GND as closer as possible. 1 2 3 4 5 6 12 11 10 9 8 7 PGND RGOOD RFB2 RFB1 13 FB RT GND RT LX L LX LX BOOT CBOOT VOUT CIN LX should be connected to inductor by wide and short trace, keep sensitive components away from this trace. COUT Output capacitor must be near RT8073 GND Figure 7. PCB Layout Guide for WDFN-12L 3x3 Connect the FB pin directly to feedback resistors. The resistor divider must be connected between VOUT and GND. CC GND RC RFB2 COMP REN CIN must be placed between VIN and GND as closer as possible. GND 2 EN 3 VIN 4 PGND 8 FB 7 RT 6 LX 5 BOOT 9 RT RFB1 VOUT GND L LX should be connected to inductor by wide and short trace, keep sensitive components away from this trace. CBOOT COUT CIN Output capacitor must be near RT8073 GND Figure 8. PCB Layout Guide for SOP-8 (Exposed Pad) Recommended component selection for Typical Application Table 2. Inductors Component Supplier Series Inductance (μH) DCR (mΩ) Wurth Elektronik No.744308033 0.33 Wurth Elektronik No.744355147 0.47 Current Rating (A) Case Size 0.37 27 1070 0.67 30 1365 Table 3. Capacitors for CIN and COUT Component Supplier TDK Part No. C3225X5R0J226M Capacitance (μF) 22 Case Size 1210 TDK C2012X5R0J106M 10 0805 Panasonic ECJ4YB0J226M 22 1210 Panasonic ECJ4YB1A106M 10 1210 TAIYO YUDEN LMK325BJ226ML 22 1210 TAIYO YUDEN JMK316BJ226ML 22 1206 TAIYO YUDEN JMK212BJ106ML 10 0805 Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 14 is a registered trademark of Richtek Technology Corporation. DS8073-01 November 2012 RT8073 Outline Dimension H A M EXPOSED THERMAL PAD (Bottom of Package) Y J X B F C I D Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 4.801 5.004 0.189 0.197 B 3.810 4.000 0.150 0.157 C 1.346 1.753 0.053 0.069 D 0.330 0.510 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.170 0.254 0.007 0.010 I 0.000 0.152 0.000 0.006 J 5.791 6.200 0.228 0.244 M 0.406 1.270 0.016 0.050 X 2.000 2.300 0.079 0.091 Y 2.000 2.300 0.079 0.091 X 2.100 2.500 0.083 0.098 Y 3.000 3.500 0.118 0.138 Option 1 Option 2 8-Lead SOP (Exposed Pad) Plastic Package Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS8073-01 November 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 15 RT8073 2 1 2 1 DETAIL A Pin #1 ID and Tie Bar Mark Options Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Symbol Dimensions In Millimeters Dimensions In Inches 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 2.950 3.050 0.116 0.120 D2 2.300 2.650 0.091 0.104 E 2.950 3.050 0.116 0.120 E2 1.400 1.750 0.055 0.069 e L 0.450 0.350 0.018 0.450 0.014 0.018 W-Type 12L DFN 3x3 Package Richtek Technology Corporation 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries. www.richtek.com 16 DS8073-01 November 2012