SY8120B1ABC

Application Note: SY8120B1 High Efficiency Fast Response, 2A, 18V Input Synchronous Step Down Regulator Features SY8120B1 develops high efficiency synchronous stepdown DC-DC converter capable of delivering 2A load current . SY8120B1 operates over a wide input voltage range from 4.5V to 18V 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):130/120 mΩ • 4.5-18V input voltage range • 2A load current capability • Instant PWM architecture to achieve fast transient responses Internal softstart limits the inrush current • 2% 0.6V reference • Cycle-by-cycle peak current limitation • RoHS Compliant and Halogen Free • Compact package: SOT23-6 Ordering Information tia l-P re p SY8120 □(□□)□ Temperature Code Package Code Optional Spec Code Temperature Range: -40°C to 85°C en Package type SOT23-6 Note -- er sta ow rp fo • • • • • • • • Set Top Box Portable TV Access Point Router DSL Modem LCD TV CCTV IP CAM Networking .C on fid Ordering Number SY8120B1ABC Applications ar ed SY8120B1 adopts the instant PWM architecture to achieve fast transient responses for high step down applications and high efficiency at light loads. In addition, it operates at pseudo-constant frequency of 500 kHz under heavy load conditions to minimize the size of inductor and capacitor. r General Description 1 2 Sil er gy Co rp Typical Applications Figure 1. Schematic Diagram AN_SY8120B1 Rev.0.9 Figure 2. Efficiency Figure Silergy Corp. Confidential-prepared for Internal Use Only 1 AN_SY8120B1 er sta r Pinout (top view) (SOT23-6) Pin Number BS 1 GND 2 FB 3 EN IN LX 4 5 6 Pin Description Boot-Strap Pin. Supply high side gate driver. Decouple this pin to LX pin with 0.1uF ceramic cap. Ground pin 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) Enable control. Pull high to turn on. Do not float. Input pin. Decouple this pin to GND pin with at least 1uF ceramic cap Inductor pin. Connect this pin to the switching node of inductor tia l-P re p ar ed fo rp Pin Name ow Top Mark: WBxyz, (Device code: WB, x=year code, y=week code, z= lot number code) en Absolute Maximum Ratings (Note 1) er gy Co rp .C on fid Supply Input Voltage ----------------------------------------------------------------------------------------- 19V LX, EN Voltage---------------------------------------------------------------------------------------- VIN + 0.3V FB, BS-LX Voltage---------------------------------------------------------------------------------------------- 4V Power Dissipation, PD @ TA = 25°C SOT23-6, ----------------------------------------------------------- 0.6W Package Thermal Resistance (Note 2) θ JA ------------------------------------------------------------------------------------------------- 170°C/W θ JC ------------------------------------------------------------------------------------------------- 75°C/W Junction Temperature Range -------------------------------------------------------------------------------- 150°C Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------- 260°C Storage Temperature Range ---------------------------------------------------------------------- -65°C to 150°C Sil Recommended Operating Conditions (Note 3) Supply Input Voltage ---------------------------------------------------------------------------------- 4.5V to 18V Junction Temperature Range --------------------------------------------------------------------- -40°C to 125°C Ambient Temperature Range ---------------------------------------------------------------------- -40°C to 85°C AN_SY8120B1 Rev.0.9 Silergy Corp. Confidential-prepared for Internal Use Only 2 AN_SY8120B1 Sil er gy Co rp .C on fid en tia l-P re p ar ed fo rp ow er sta r Block Diagram AN_SY8120B1 Rev.0.9 Silergy Corp. Confidential-prepared for Internal Use Only 3 AN_SY8120B1 Electrical Characteristics (VIN = 12V, VOUT = 1.2V, L = 2.2uH, COUT = 10uF, TA = 25°C, IOUT = 1A unless otherwise specified) Symbol VIN IQ ISHDN Test Conditions Min 4.5 IOUT=0, VFB=VREF×105% EN=0 0.588 VREF -50 er sta VFB=VIN tia l-P re p ar ed fo rp ILIM,BOTTOM tSS TSD 10 0.612 Unit V µA µA V 50 nA Ω Ω 3.6 A 2 A 1.5 500 50 100 800 150 V V V kHz ns ns us C 15 C 0.4 4.5 en THYS Max 18 0.13 0.12 ILIM,TOP VENH VENL VUVLO FSW 400 5 0.6 ow IFB RDS(ON)1 RDS(ON)2 Typ r Parameter Input Voltage Range Quiescent Current Shutdown Current Feedback Reference Voltage FB Input Current Top FET RON Bottom FET RON TOP FET Peak Current Limit Bottom FET Valley Current Limit EN Rising Threshold EN Falling Threshold Input UVLO Threshold Switching Frequency Min ON Time Min Off Time Soft-start Time Thermal Shutdown Temperature Thermal Shutdown Hysteresis .C on fid Note 1: Stresses beyond “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 may affect device reliability. Co rp Note 2: θ JA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Pin 2 of SOT-23-6 packages is the case position for θ JC measurement. Sil er gy Note 3: The device is not guaranteed to function outside its operating conditions. AN_SY8120B1 Rev.0.9 Silergy Corp. Confidential-prepared for Internal Use Only 4 AN_SY8120B1 Sil er gy Co rp .C on fid en Efficiency (%) tia l-P re p ar ed fo rp ow er sta r Efficiency (%) Efficiency (%) Typical Performance Characteristics AN_SY8120B1 Rev.0.9 Silergy Corp. Confidential-prepared for Internal Use Only 5 fo rp ow er sta r AN_SY8120B1 1A/div tia l-P re p IL en 2V/div (VIN=12V, VOUT=3.3V, 2A to Short) VOUT 2V/div IL 1A/div .C on fid VOUT Short Circuit Protection ar ed Short Circuit Protection (VIN=12V, VOUT=3.3V, Open to Short) Time (2ms/div) Sil er gy Co rp Time (2ms/div) AN_SY8120B1 Rev.0.9 Silergy Corp. Confidential-prepared for Internal Use Only 6 AN_SY8120B1 r 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: rp SY8120B1 provides protection functions such as cycle by cycle current limiting and thermal shutdown protection. SY8120B1 will sense the output voltage conditions for the fault protection. 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. er sta SY8120B1 is a synchronous buck regulator IC that integrates the PWM control, top and bottom switches on the same die to minimize the switching transition loss and conduction loss. With ultra low Rds(on) power switches and proprietary PWM control, this regulator IC can achieve the highest efficiency and the highest switch frequency simultaneously to minimize the external inductor and capacitor size, and thus achieving the minimum solution footprint. minimize the loop area formed by CIN, and IN/GND pins. In this case, a 4.7uF low ESR ceramic capacitor is recommended. ow Operation fo Applications Information tia l-P re p ar ed Because of the high integration in the SY8120B1 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: .C on fid en 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: 0.6VFB GND Input capacitor CIN: Sil ISAT, MIN > IOUT, MAX + R1 R2 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 VOUT (1 − VOUT /VIN, MAX ) FSW × I OUT, MAX × 40% where Fsw is the switching frequency and IOUT,MAX is the maximum load current. The SY8120B1 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. VOUT er gy Co rp 0.6V R2 = R1 . VOUT − 0.6V L= 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