SY8303AIC

Applications Note: SY8303 High Efficiency Fast Response, 3A, 40V Input Synchronous Step Down Regulator General Description Features The SY8303 develops a high efficiency synchronous step-down DC-DC converter capable of delivering 3A load current. The SY8303 operates over a wide input voltage range from 4.5V to 40V and integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. • Low RDS(ON) for internal switches (top/bottom): 110/70 mΩ • 4.5-40V input voltage range • Internal compensation • Internal 1ms soft-start limits the inrush current • Adjustable switching frequency range: 500kHz to 2.5MHz • 3A output current capability • 1.5% 0.6V reference • Low quiescent current • Cycle-by-cycle peak current limitation • Short circuit protection • Thermal shutdown and auto recovery • RoHS Compliant and Halogen Free • Compact package: TSOT23-8 The SY8303 adopts peak current control scheme. The switching frequency is adjustable from 500kHz to 2.5MHz using an external resistor. The device also features ultra low quiescent operating to achieve high efficiency under light load. And the internal soft-start limits inrush current during power on. SY8303 is available in TSOT23-8 package. Ordering Information Applications SY8303 □(□□ □□)□ □□ □ Tempera ture Code Packa ge Code Optiona l Spec Code Ordering Number SY8303AIC Package type TSOT23-8 Note -- • • • • • • LCD-TV SetTop Box Notebook Storage High Power AP Router Networking Typical Applications Figure 1. Schematic Diagram AN_SY8303 Rev. 0.9A Figure 2. Efficiency vs. Load Current Silergy Corp. Confidential- Prepared for Customer Use Only 1 SY8303 Pinout (top view) Top Mark: Pin Name FB Pin Number 1 FS 2 EN 8 GND 3,4 IN LX BS 5 6 7 FB 1 8 EN FS 2 7 BS GND 3 6 LX GND 4 5 IN XDxyz (Device code: XD, x=year code, y=week code, z= lot number code) Pin Description 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) Frequency programming pin. Connect a resistor to ground to program a switching frequency between 500kHz to 2.5MHz. The switching frequency equals to: Fsw=105/RFS kHz, where RFS is in kΩ . Enable control. Pull high to turn on. Do not float. Ground pin. Input pin. Decouple this pin to GND pin with at least 4.7uF ceramic cap. Inductor pin. Connect this pin to the switching node of inductor. Boot-strap pin. Supply high side gate driver. Decouple this pin to LX pin with 10nF ceramic cap. Absolute Maximum Ratings (Note 1) IN to GND ----------------------------------------------------------------------------------------------- -0.3V to 40V LX, FB, EN, FS to GND------------------------------------------------------------------------------------------ -0.3V to 40V BS-LX ------------------------------------------------------------------------------------------- 4V Power Dissipation, PD @ T A = 25°C TSOT23-8 ------------------------------------------------------------ 2W Package Thermal Resistance (Note 2) θ JA -------------------------------------------------------------------------------------------------------------- 60.2°C/W θ JC --------------------------------------------------------------------------------------------------------------- 11.2°C/W Junction Temperature Range ------------------------------------------------------------------------------------------------ 150°C Ambient Temperature Range ------------------------------------------------------------------------------------- -40°C to 105°C Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------------ 260°C Storage Temperature Range -------------------------------------------------------------------------------------- -65°C to 150°C Recommended Operating Conditions (Note 3) Supply Input Voltage -------------------------------------------------------------------------------------------------- 4.5V to 40V AN_SY8303 Rev. 0.9A Silergy Corp. Confidential- Prepared for Customer Use Only 2 SY8303 Electrical Characteristics (VIN = 12V, VOUT = 5V, COUT = 47uF, TA = 25°C, IOUT = 1A unless otherwise specified) Parameter Input Voltage Range Quiescent Current Shutdown Current Feedback Reference Voltage FB Input Current Top FET RON Bottom FET RON Top FET Current Limit EN Low threshold EN High Threshold Input UVLO threshold UVLO hysteresis Oscillator Frequency Program Range Oscillator Frequency Accuracy Soft-start Time Min ON Time Min OFF Time Thermal Shutdown Temperature Thermal Shutdown Hysteresis Symbol VIN IQ ISHDN VREF IFB RDS(ON)1 RDS(ON)2 ILIM,TOP VENL VENH VUVLO VHYS FOSC Test Conditions Min 4.5 IOUT=0, VFB=VREF*105% EN=0 0.591 VFB=VCC Typ 1 0.6 -50 Max 40 18 2 0.609 Unit V µA µA V 50 nA mΩ mΩ A V V V V MHz 110 70 4 0.6 6.8 1.5 4.35 0.2 0.5 RFS=200k -15 TSS 15 %FOSC TSD 1 80 120 150 ms ns ns °C TSD,HYS 15 °C Note 1: Stresses beyond the “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Note 2: θ JA is measured in the natural convection at TA = 25°C on a low effective 4-layer thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Pin 2 of TSOT-23-8 packages is the case position for θ JC measurement. Note 3: The device is not guaranteed to function outside its operating conditions. AN_SY8303 Rev. 0.9A Silergy Corp. Confidential- Prepared for Customer Use Only 3 SY8303 Typical Performance Characteristics Load Transient Efficiency vs. Load Current (VIN=12V, VOUT=5V, IOUT=0.3A ~ 3A) 100 ∆VOUT Efficiency (%) 80 0.5V/div 60 40 IL 2A/div VIN=9V, VOUT=5V VIN=12V, VOUT=5V VIN=24V, VOUT=5V VIN=40V, VOUT=5V 20 0 1 10 100 1000 Load Current (mA) 10000 Time (40µs/div) Startup from VIN Shutdown from VIN (VIN=12V, VOUT=5V, IOUT=3A) (VIN=12V, VOUT=5V, IOUT=3A) VIN 10V/div VIN 10V/div VLX 10V/div VLX 10V/div 2V/div VOUT 2V/div 2A/div IL 2A/div VOUT IL Time (4ms/div) Time (20ms/div) Startup from Enable Shutdown from Enable (VIN=12V, VOUT=5V, IOUT=3A) (VIN=12V, VOUT=5V, IOUT=3A) EN 5V/div EN 5V/div VLX 10V/div VLX 10V/div 2V/div VOUT 2V/div 2A/div IL 2A/div VOUT IL Time (4ms/div) AN_SY8303 Rev. 0.9A Time (100µs/div) Silergy Corp. Confidential- Prepared for Customer Use Only 4 SY8303 Short Circuit Protection Short Circuit Protection (VIN=12V, VOUT=5V, Null Load to Short) (VIN=12V, VOUT=5V, 3A to Short) Signal 10V/div Signal 10V/div VOUT 5V/div VOUT 5V/div IL 5A/div IL 5A/div Time (20ms/div) Time (20ms/div) Output Ripple (VIN=12V, VOUT=5V, IOUT= 3A) ∆VOUT 10mV/div VLX 10V/div IL 2A/div Time (2µs/div) AN_SY8303 Rev. 0.9A Silergy Corp. Confidential- Prepared for Customer Use Only 5 SY8303 pins. In this case, a 4.7uF low ESR ceramic capacitor is recommended. Operation The SY8303 develops a high efficiency synchronous step-down DC-DC converter capable of delivering 3A load current. The SY8303 operates over a wide input voltage range from 4.5V to 40V and integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. The SY8303 adopts peak current control scheme. The switching frequency is adjustable from 500kHz to 2.5MHz using an external resistor. The device also features ultra low quiescent operating to achieve high efficiency under light load. And the internal soft-start limits inrush current during power on. Applications Information Because of the high integration in the SY8303 IC, the application circuit based on this regulator IC is rather simple. Only input capacitor CIN, output capacitor COUT, output inductor L and feedback resistors (R1 and R2) need to be selected for the targeted applications specifications. Feedback resistor dividers R1 and R2: Choose R1 and R2 to program the proper output voltage. To minimize the power consumption under light loads, it is desirable to choose large resistance values for both R1 and R2. A value of between 10kΩ and 1MΩ is highly recommended for both resistors. If Vout is 3.3V, R1=100k is chosen, then using following equation, R2 can be calculated to be 22.1k: Output capacitor COUT: The output capacitor is selected to handle the output ripple noise requirements. Both steady state ripple and transient requirements must be taken into consideration when selecting this capacitor. For the best performance, it is recommended to use X5R or better grade ceramic capacitor greater than 22uF capacitance. Output inductor L: There are several considerations in choosing this inductor. 1) Choose the inductance to provide the desired ripple current. It is suggested to choose the ripple current to be about 40% of the maximum output current. The inductance is calculated as: L= where Fsw is the switching frequency and IOUT,MAX is the maximum load current. The SY8303 regulator IC is quite tolerant of different ripple current amplitude. Consequently, the final choice of inductance can be slightly off the calculation value without significantly impacting the performance. 2) The saturation current rating of the inductor must be selected to be greater than the peak inductor current under full load conditions. ISAT, MIN > IOUT, MAX + VOUT R2 = 0.6V R1 . VOUT − 0.6V R1 0.6VFB GND R2 Input capacitor CIN: The ripple current through input capacitor is calculated as： I CIN _ RMS = I OUT ⋅ D(1 − D) . To minimize the potential noise problem, place a typical X5R or better grade ceramic capacitor really close to the IN and GND pins. Care should be taken to minimize the loop area formed by CIN, and IN/GND VOUT (1 − VOUT /VIN, MAX ) FSW × I OUT, MAX × 40% 3) VOUT(1-VOUT/VIN,MAX) 2 ⋅ FSW ⋅ L The DCR of the inductor and the core loss at the switching frequency must be low enough to achieve the desired efficiency requirement. It is desirable to choose an inductor with DCR