XC8020

XenCreator XC8020 High-Efficiency,2A,1.2MHz Synchronous,Step-Down Converter FEATURES GENERAL DESCRIPTION The XC8020 is a high-frequency, synchronous, rectified, step-down, switch-mode converter with internal power MOSFETs. It offers a very compact solution to achieve a 2A continuous output current over a wide input supply range, with excellent load and line regulation. The XC8020 has synchronous-mode operation for higher efficiency over the output current-load range. Current-mode operation provides fast transient response and eases loop stabilization. Protection features include over-current protection and thermal shutdown. The XC8020 requires a minimal number of readily available, standard, external components and is available in a space-saving 5-pin SOT23 package. ● ● ● ● ● ● ● ● ● ● 110mΩ/90mΩ Low-RDS(ON) Internal Power MOSFETs High-Efficiency Synchronous-Mode Operation Fixed 1.2MHz Switching Frequency PFM Mode for High Efficiency at Light Load Internal Soft-Start Input Voltage UVP & OVP Over-Current Protection and Hiccup Thermal Shutdown Output Adjustable from 0.6V Available in a 5-pin SOT-23 package APPLICATIONS ● Digital Set-top Box (STB) ● Tablet Personal Computer (Pad) ● Flat-Panel Television and Monitors ● Digital Video Recorder (DVR) ● Portable Media Player (PMP) ● General Purposes TYPICAL APPLICATIONS VIN VIN SW R1 200k 1% XC8020 CIN 10μF XC8020 Rev.1.20 VOUT L 2.2μH EN FB R2 100k 1% GND -1- C1 22pF opt. COUT 10μF XenCreator XC8020 PACKAGE/ORDER INFORMATION EN 1 GND 2 SW 3 5 4 Order Part Number Package XC8020 SOT23-5 FB VIN FUNCTIONAL PIN DESCRIPTION PIN 1 NAME EN TYPE I FUNCTION DESCRIPTIONS 2 GND G Pull High to enable the XC8020. For automatic start-up, connect EN to VIN using a 100kΩ resistor. Do not float. System Ground. Reference ground of the regulated output voltage:requires extra care during PCB layout. Connect to GND with copper traces and vias. 3 SW I/O Switch Output. Connect using a wide PCB trace. 4 VIN PI Supply Voltage. The XC8020 operates from a 2.3V-to-6V input rail. Requires C1 to decouple the input rail. Connect using a wide PCB trace. 5 FB I Output Feedback Pin. Connect this pin to the center point of the output resistor divider (as shown in Figure 1) to program the output voltage: VOUT=0.6×(1+R1/R2). XC8020 Rev.1.20 -2- XenCreator XC8020 FUNCTION BLOCK DIAGRAM EN VIN RS OSC & Shutdown Control Current Limit Detector PWM/PFM Mode Detector Slope Compensation Current Sensor Control Logic PWM Compartor FB Driver SW Error Amplifier Zero Detector GND UVLO & Power Good Detector VREF ABSOLUTE MAXIMUM RATINGS PARAMETER ABSOLUTE MAXIMUM RATINGS UNIT VIN -0.3 to 6 V VSW -0.3 to 6 V VEN -0.3 to 6 V VFB -0.3 to 6 V Continuous Power Dissipation(TA=+25℃) 1.25 W Junction Temperature 150 °C Lead Temperature 260 °C -65 to 150 °C Storage Temperature Thermal Resistance θJA 100 °C /W Thermal Resistance θJC 55 °C /W ESD Susceptibility(HBM) 2 XC8020 Rev.1.20 -3- kV XenCreator XC8020 RECOMMENDED OPERATING CONDITIONS PARAMETER RECOMMENDED UNIT Supply Voltage VIN 2.5 to 5.5 V Output Voltage VOUT 0.6 to VIN V Operating Junction Temp.(TJ) -40 to 125 °C ELECTRICAL CHARACTERISTICS PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT 1 uA Supply Current(Shutdown) IIN VEN=0V 0.1 Supply Current(Quiescent) Iq VEN = 2V, VFB = 1V 40 uA HS Switch-On Resistance HSRDS-ON 110 mΩ LS Switch-On Resistance LSRDS-ON 90 mΩ Switch Leakage Current Limit SW LKG VEN = 0V, VSW = 5V 1 ILIMIT Oscillator Frequency fSW Feedback Voltage VFB VFB=0.75V 588 uA 2.5 A 1.2 MHz 600 612 mV EN Input Voltage High VEN_HIGH 1.5 V EN Input Voltage Low VEN_LOW 0.4 V EN Input Current IEN VEN=2V VEN=0V VIN UVP Threshold— Rising VINUVFALL VIN UVP Threshold Hysteresis VIN OVP Threshold— Rising VIN OVP Threshold Hysteresis Thermal Shutdown VINOVRISE uA 2.4 V 300 mV 200 -4- uA 0 6 Thermal Hysteresis XC8020 Rev.1.20 1 V mV 150 °C 20 °C XenCreator XC8020 TYPICAL PERFORMANCE CHARACTERISTICS OUTPUT VOLTAGE VS OUTPUT CURRENT (VOUT=3.3V) EFFICIENCY VS OUTPUT CURRENT (VOUT=3.3V) 100% 4.1 90% 3.6 OUTPUT VOLTAGE(V) EFFICIENCY 80% 70% 60% VIN=5V 50% 3.1 2.6 2.1 VIN=5V 1.6 40% 30% 0 500 1000 1500 1.1 2000 0 OUTPUT CURRENT(mA) 1000 OUTPUT CURRENT(mA) 1500 STEADY STATE OPERATION (VIN=5V,VOUT=3.3V,IOUT=2000mA) STEADY STATE OPERATION (VIN=5V,VOUT=3.3V,IOUT=100mA) LOAD TRANSIENT RESPONSE (VIN=5V,VOUT=3.3V,IOUT=500-1500mA,1A/uS) XC8020 Rev.1.20 500 STRAT UP (VIN=5V,VOUT=3.3V) -5- 2000 XenCreator XC8020 OPERATION External Components Selection XC8020 require an input capacitor, an output capa citor and an inductor. These componen ts are critical to the performance of the device. XC8020 are internally comp -ensated and do not require external components to ach VOUT -ieve stable operation. The output voltage can be progra -mmed by resistor divider. R1 𝑉𝑂𝑈𝑇 = 𝑉𝐹𝐵 × COUT VFB 𝑅1+ 𝑅2 𝑅2 R2 Select R1 value around 50kΩ 𝑅2 = 𝑅1× 𝑉𝐹𝐵 𝑉𝑂𝑈𝑇 − 𝑉𝐹𝐵 Where 𝑉𝐹𝐵 as 0.6V Output Inductors and Capacitors Selection BUCK Power Supply Recommendations There are several design considerations related to the sel -ection of output inductors and capacitors: • Load transient response • Stability supply must be well regulated. If the input supply is located more than a few inches, additional bulk capacitance may be required in addition to the XC8020 are designed to operate from input voltag e supply range between 2.3 V and 6 V. This inpu t ceramic bypass capacitors. An ceramic capacitor with a value of 10uF is a typical choice. • Efficiency • Output ripple voltage • Over current ruggedness The device has been optimized for use with nominal LC values as shown in the Application Diagram. VIN must be connected to input capacitors as close as possible. 𝐼𝐿(𝑀𝐴𝑋) = 𝐼𝐿𝑂𝐴𝐷(𝑀𝐴𝑋) + 𝐼𝑅 BUCK Inductor Selection The recommended inductor values are shown in the Appli -cation Diagram. It is important to guarantee the inductor core does not saturate during any foreseeable operational sit uation. The inductor should be rated to handle the peak load current plus the ripple current: Care should be taken when reviewing the different saturation current ratings that are specified by different manu facturers. Saturation current ratings are typically specified at 25°C, so ratings at maximum ambient temperature of the application should be requested from the manufacturer. XC8020 Rev.1.20 -6- = 𝐼𝐿𝑂𝐴𝐷(𝑀𝐴𝑋) + D= 𝐷×( 𝑉𝐼𝑁 − 𝑉𝑂𝑈𝑇 ) 2× 𝐿× 𝐹𝑆 𝑉𝑂𝑈𝑇 , 𝐹 = 1.5 𝑀𝐻𝑧, 𝐿 = 2.2 𝑢𝐻 𝑉𝐼𝑁 𝑆 where • IL(MAX) ：Max inductor Current • ILOAD(MAX) ：Max load current • IR ：Peak-to-Peak inductor current • D ：Estimated duty factor • VIN ：Input voltage • VOUT ：Output voltage • FS ：Switching frequency, Hertz XenCreator XC8020 Recommended Method for BUCK Inductor Selection The best way to guarantee the inductor does not saturate is to choose an inductor that has saturation current rating greater than the maximum device current limit, as specified in the Electrical Characteristics. In this case the device will prevent inductor saturation by going into current limit before the saturation level is reached. Alternate Method for BUCK Inductor Selection If the reco mm ende d approach cannot be used care must be taken to guarantee that the saturation current is greater than the peak inductor current: where • ISAT：Inductor saturation current at operating temperature 𝐼𝑆𝐴𝑇 > 𝐼𝐿𝑃𝐸𝐴𝐾 • ILPEAK：Peak inductor current during worst case conditions • IOUTMAX：Maximum average inductor current 𝐼𝑅 𝐼𝐿𝑃𝐸𝐴𝐾 = 𝐼𝑂𝑈𝑇𝑀𝐴𝑋 + • IR ：Peak-to-Peak inductor current 2 • VOUT：Output voltage 𝐷 × (𝑉𝐼𝑁 − 𝑉𝑂𝑈𝑇 ) • VIN：Input voltage 𝐼𝑅 = 𝐿 × 𝐹𝑆 • L ：Inductor value in Henries at IOUTMAX • FS：Switching frequency, Hertz 𝑉𝑂𝑈𝑇 • D ：Estimated duty factor 𝐷= 𝑉𝐼𝑁 × 𝐸𝐹𝐹 • EFF：Estimated power supply efficiency ISAT may not be exceeded during any operation, including transients, startup, high temperature, worst case conditions , etc. Output and Input Capacitors Characteristics Special attention should be paid when selecting these components. The DC bias of these capacitors can result in a capacitance value that falls below the minimum value given in the recommended capacitor specifications table. The ceramic capacitor’s actual capacitance can vary with temperature. The capacitor type X7R, which operates over a temperature range of −55°C to +125°C, will only vary the capacitance to within ±15%. The capacitor type X5R has a similar tolerance over a reduced temperature range of −55°C to +85°C. Many large value ceramic capacitors, larger than 1uF are manufactured with Z5U or Y5V temperature characteristics. Their capacitance can drop by more than 50% as the temperature varies from 25°C to 85°C. Therefore X5R or X7R is recommended over Z5U and Y5V in applications where the ambient temperature will change significantly above or below 25°C. Tantalum capacitors are less desirable than ceramic for use as output capacitors because they are more expensive when comparing equivalent capacitance and voltage ratings in the 0.47uF to 44uF range. Another important consideration is that tantalum capacitors have higher ESR values than equivalent size ceramics. This means that while it may be possible to find a tantalum capacitor with an ESR value within the stable range, it would have to be larger in capacitance (which means bigger and more costly) than a ceramic capacitor with the same ESR value. It should also be noted that the ESR of a typical tantalum will increase about 2:1 as the temperature goes from 25°C down to −40°C, so some guard band must be allowed . BUCK Output Capacitor Selection The output capacitor of a switching converter absorbs the AC ripple current from the inductor and provides the initial response to a load transient. The ripple voltage at the output of the converter is the product of the ripple current flowing through the output capacitor and the impedance of the capacitor. The impedance of the capacitor can be dominated by capacitive, resistive, or inductive elements within the capacitor, depending on the frequency of the ripple current. Ceramic capacitors have very low ESR and remain capacitive up to high frequencies. Their inductive component can be usually neglected at the frequency ranges the switcher op erates . The output-filter capacitor smoothes out the current flow from the inductor to the load and helps maintain a steady output voltage during transient load changes. It also reduces output voltage ripple. These capacitors must be selected with sufficient capacitance and low enough ESR to perform these func tions. Note that the output voltage ripple increases with the inductor current ripple and the Equivalent Series Resistance of the ou tput capacitor (ESRCOUT).Also note that the actual value of the capacitor’s ESRCOUT is frequency and temperature dependent, as specified by its manufacturer. The ESR should be calculated at the applicable switching frequency and ambient temperature. XC8020 Rev.1.20 -7- XenCreator XC8020 BUCK Output Capacitor Selection 𝑉𝑂𝑈𝑇−𝑅 − 𝑃𝑃 = where Output ripple can be estimated from the vector sum of the reactive (capacitance ) voltage compon ent and the real (ESR) voltage compon ent of the output capacitor: 𝐼𝑅 8 × 𝐹𝑆 × 𝐶𝑂𝑈𝑇 2 2 + 𝑉𝐶𝑂𝑈𝑇 VOUT-R-PP = �𝑉𝑅𝑂𝑈𝑇 𝐷 × (𝑉𝐼𝑁 − 𝑉𝑂𝑈𝑇 ) 2 × 𝐿 × 𝐹𝑆 𝑉𝑂𝑈𝑇 𝐷= 𝑉𝐼𝑁 𝐼𝑅 = where 𝑉𝑅𝑂𝑈𝑇 = 𝐼𝑅 × 𝐸𝑆𝑅𝐶𝑂𝑈𝑇 𝑉𝐶𝑂𝑈𝑇 = where • VOUT-R -PP：estimated output ripple, • IR ：estimated current ripple • D：Estimated duty factor 𝐼𝑅 8 × 𝐹𝑆 × 𝐶𝑂𝑈𝑇 where • VOUT-R -PP：estimated output ripple, • VROUT：estimated real output ripple, • VCOUT：estimated reactive output ripple. The device is designed to be used with ceramic capacitors on the outputs of the buck regulators. The recommended dielec tric type of these capacitors is X5R, X7R, or of comparable material to maintain proper tolerances over voltage and temperature. The recommended value for the output capacitors is 10µF, 6.3V with an ESR of 2mΩ or less. The output capacitors need to mounted as close as possible to the output/ground terminals of the device. BUCK Input Capacitor Selection input capacitor should be located as close as possible to their corresponding VIN and GND terminals, tantalum capacitor can also be located in the proximity of the device. The input capacitor supplies the AC switching current drawn from the switching action of the internal power MOSFETs. The input current of a buck converter is discontinuous, so the ripple current supplied by the input capacitor is large. The input capacitor must be rated to handle both the RMS current and the dissipated power. The input capacitor must be rated to handle this current: 𝑉𝑅𝑀𝑆_𝐶𝐼𝑁 = 𝐼𝑂𝑈𝑇 -ntain proper tolerances over voltage and temperature. The min -imum recommended value for the input capacitor is 10µF with an ESR of 10mΩ or less. The input capacitors need to be mount -ed as close as possible to the power/ground input terminals of the device.The input power source supplies the average current continuously. During the high side MOSFET switch on-time, how -ever,the demanded di/dt is higher than can be typically supplied by the input power source. This delta is supplied by the input cap -acitor.A simplified “worst case” assumption is that all of the high side MOSFET current is supplied by the input capacitor. This will Result in conservative estimates of input ripple voltage and cap a -citor RMS Current. Input ripple voltage is estimated as besides: This capacitor is exposed to significant RMS current, so it is import -ant to select a capacitor with an adequate RMS current rating. Capacitor RMS current estimated as besides: XC8020 Rev.1.20 -8- 𝑉𝑂𝑈𝑇 The power dissipated in the input capacitor is given by: 2 × 𝑅𝐸𝑆𝑅_𝐶𝐼𝑁 𝑃𝐷_𝐶𝐼𝑁 = 𝐼𝑅𝑀𝑆_𝐶𝐼𝑁 The device is designed to be used with ceramic capacitors on the inputs of the buck regulators. The recomm ended dielectric type of these capacitors is X5R, X7R, or of comparable material to mai �𝑉𝑂𝑈𝑇 × (𝑉𝐼𝑁 − 𝑉𝑂𝑈𝑇 ) 𝑉𝑃𝑃𝐼𝑁 = where 𝐼𝑂𝑈𝑇 × 𝐷 + 𝐼𝑂𝑈𝑇 × 𝐸𝑆𝑅𝐶𝐼𝑁 𝐶𝐼𝑁 × 𝐹𝑆 • VPPIN：Estimated peak-to-peak input ripple voltage • IOUT ：Output current • CIN：Input capacitor value • ESRCIN ：Input capacitor ESR 2 𝐼𝑅𝑀𝑆𝐶𝐼𝑁 = �𝐷 × (𝐼𝑂𝑈𝑇 + 2 𝐼𝑅𝐼𝑃𝑃𝐿𝐸 ) 12 Where •IRMSCIN ：Estimated input capacitor RMS current XenCreator XC8020 PC BOARD LAYOUT PC board layout is an important part of DC-DC converter design.Poor board layout can disrupt the performance of a DCDC converter and surrounding circuitry by contributing to EMI, ground bounce, and resistive voltage loss in the traces. These can send erroneous signals to the DC-DC converter resulting in poor regulation or instability. Good layout can beimplemented by following a few simple design rules. 1. Minimize area of switched current loops. In a buck regulat or there are two loops where currents are switched rapidly. The first loop starts from the CIN input capacitor, to the regu -lator VIN terminal, to the regulator SW terminal, to the induc tor then out to the output capacitor C OUT and load. The seco -nd loop starts from the output capacitor ground, to the regu l -ator GND terminals, to the inductor and then out to COUT and the load. To minimize both loop areas the input capacitor should be placed as close as possible to the VIN terminal. 2. Minimize the copper area of the switch node. The SW terminals should be directly connected with a trace that runs on top side directly to the inductor. To minimize IR losses this trace should be as short as possible and with a sufficient width. However, a trace that is wider than 100 mils will increase the copper area and cause too much capacitive loading on the SW terminal. The induc -tors should be placed as close as possible to the Grounding for both the input and output capacitors shou ld SW terminals to further minimize the copper area of the switch node. 3. Have a single point ground for all device analog grounds. The ground connections for the feedback com ponents should be connected together then routed to the GND pin of the device. This prevents any switched or load curren ts from flowing in the analog ground plane. If not properly 4. Minimize trace length to the FB terminal. The fe -edback trace should be routed away from the SW pin and inductor to avoid contaminating the feedba -ck signal with switch noise. 5. Make input and output bus connections as wide consist of a small localized top side plane that connects to GND. The inductor should be placed as close as possible to the SW pin and output capacitor. handled, poor grounding can result in degraded load regul -ation or erratic switching behavior. as possible. This reduces any voltage drops on the input or output of the converter and can improv -e efficiency. If voltage accuracy at the load is impo -rtant make sure feedback voltage sense ismade at the load. Doing so will correct for voltage drops at the load and provide the best output accuracy. XC8020 Rev.1.20 - 9- XenCreator XC8020 PACKAGE SOT23-5 e1 5LD SOT-23 PACKAGE OUTLINE DIMENSIONS Dimension A A1 B C D H E e e1 L1 L Q EXAMPLE TOP MARK AAAA E H PIN 1 Min. 1.05 0.04 0.3 0.09 2.8 2.5 1.5 Max. 1.35 0.15 0.5 0.2 3.0 3.1 1.7 0.95 REF. 1.90 REF. 0.2 0.35 0° 0.55 0.8 10° TOP VIEW D L A SEATING PLANE B e L1 A1 FRONT VIEW C SIDE VIEW NOTE: 1.DIMENSIONS ARE IN MILLIMETERS 2.DRAWING NOT TO SCALE 3.DIMENSIONS ARE INCLUSIVE OF PLATING 4.DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR XC8020 Rev.1.20 Q - 10 -