SY8120IABC

Application Note: SY8120I High Efficiency, Fast Response, 2.0A, 18V Input Synchronous Step Down Regulator General Description Features The SY8120I is a high efficiency, synchronous stepdown DC/DC converter capable of delivering 2A load current. The SY8120I operates over a wide input voltage range from 4.2V to 18V and integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. The SY8120I 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 500kHz to minimize the size of inductor and capacitor. Ordering Information SY8120 □(□□)□ Tempera ture Code Packa ge Code Optional Spec Code Package type Note SOT23-6 ---- Ordering Number SY8120IABC • • • • • • • • • • • Low RDS(ON) for Internal Switches (Top/Bottom): 130mΩ/105mΩ 4.2-18V Input Voltage Range 2A Output Current Capability 500kHz Switching Frequency Minimize the External Components Stable with 10µF COUT and 1.5µH Inductor Instant PWM Architecture to Achieve Fast Transient Responses Internal Soft-start Limits the Inrush Current Cycle-by-cycle Peak/Valley Current Limitation Hic-cup Mode Output Short Circuit Protection Thermal Shutdown with Auto Recovery Compact Package SOT23-6 Applications • • • • • • Set Top Box Portable TV DSL Modem LCD TV IP CAM Networking Typical Application Figure1. Schematic Diagram Inductor and COUT Selection Table VOUT [V] L [µH] 1.5 3.3 2.2 4.7 3.3 6.8 4.7 COUT [µF] 10 22 √ √ ☆ √ √ 3.3 √ ☆ √ √ 5 √ ☆ Note: ‘☆’ means recommended for most applications. 1.2 AN_SY8120I Rev0.9 © 2018 Silergy Corp. √ Figure2. Efficiency vs. Load Current Silergy Corp. Confidential- Prepared for Customer Use Only 1 All Rights Reserved. AN_SY8120I Pin-out (top view) (SOT23-6) Top mark: qGxyz (Device code:qG, x=year code, y=week code, z= lot number code) Pin Name Pin Number BS 1 GND 2 FB 3 EN 4 Pin Description Boot-strap pin. Supply high side gate driver. Connect a 0.1µF ceramic capacitor between BS and LX pin. Power 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+RH/RL). Enable control. Pull high to turn on. Do not leave this pin floating. IN 5 Input pin. Decouple this pin to GND pin with at least a 10µF ceramic capacitor. LX 6 Inductor pin. Connect this pin to the switching node of inductor. Block Diagram AN_SY8120I Rev0.9 © 2018 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 2 All Rights Reserved. AN_SY8120I Absolute Maximum Ratings (Note 1) Supply Input Voltage ------------------------------------------------------------------------------------------------- -0.3V to 19V LX, EN Voltage--------------------------------------------------------------------------------------------- -0.3V to VIN + 0.3V FB, BS-LX Voltage----------------------------------------------------------------------------------------------------- -0.3V to 4V Power Dissipation, PD @ TA = 25°C SOT23-6, ------------------------------------------------------------------------------ 1W Package Thermal Resistance (Note 2) θ JA --------------------------------------------------------------------------------------------------------- 100°C/W θ JC ----------------------------------------------------------------------------------------------------------- 25°C/W Junction Temperature Range ------------------------------------------------------------------------------------- -40°C to 150°C Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------------------- 260°C Storage Temperature Range ------------------------------------------------------------------------------- -65°C to 150°C Dynamic LX voltage in 10ns duration (Note3) ---------------------------------------------------- IN+3V to GND-5V Recommended Operating Conditions (Note 3) Supply Input Voltage ------------------------------------------------------------------------------------------- 4.2V to 18V Junction Temperature Range ------------------------------------------------------------------------------- -40°C to 125°C Ambient Temperature Range ------------------------------------------------------------------------------- -40°C to 85°C AN_SY8120I Rev0.9 © 2018 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 3 All Rights Reserved. AN_SY8120I Electrical Characteristics (VIN = 12V, VOUT = 3.3V, L = 4.7µH, COUT = 10µF, TA = 25°C, IOUT = 1A unless otherwise specified) Parameter Input Voltage Range Input UVLO Threshold Input UVLO Hysteresis Quiescent Current Shutdown Current Feedback Reference Voltage FB Input Current Top FET RON Bottom FET RON EN Rising Threshold EN Falling Threshold Min ON Time Min OFF Time Turn On Delay Soft-start Time Switching Frequency Top FET Current Limit Bottom FET Current Limit Output Under Voltage Protection Threshold Output UVP Delay UVP Hiccup On Time UVP Hiccup Off Time Thermal Shutdown Temperature Thermal Shutdown Hysteresis Symbol VIN VUVLO VHYS IQ ISHDN Test Conditions Min 4.2 IOUT=0, VFB=VREF×105% EN=0 591 VREF IFB RDS(ON)1 RDS(ON)2 VEN, R VEN, F tON,MIN tOFF,MIN tON,DLY tSS fSW VFB=3.3V Typ 0.3 200 5 10 Unit V V V µA µA 600 609 mV 50 nA mΩ mΩ V V ns ns µs ms kHz -50 1.08 0.9 from EN high to LX start switching VOUT from 0 to 100% IOUT=1A 130 105 1.2 1.0 50 100 300 1 500 Max 18 4.15 1.32 1.1 ILMT,TOP 3 A ILMT,BOT 2 A VUVP 0.33 VREF tUVP,DLY tUVP,ON tUVP,OFF 200 1.4 5.2 µs ms ms TSD 150 ˚C THYS 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 2OZ two-layer Silergy evaluation board. Paddle of SOT23-6 package is the case position for SY8120I θ JC measurement. Note 3: The device is not guaranteed to function outside its operating conditions. AN_SY8120I Rev0.9 © 2018 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 4 All Rights Reserved. AN_SY8120I Typical Performance Characteristics Efficiency vs. Load Current 100 Efficiency (%) 90 80 70 60 50 VIN=5V, VOUT=1.8V VIN=12V, VOUT=1.8V VIN=18V, VOUT=1.8V 40 30 0.01 0.1 1 10 Load Current (A) AN_SY8120I Rev0.9 © 2018 Silergy Corp. Silergy Corp. Confidential- Prepared for Customer Use Only 5 All Rights Reserved. AN_SY8120I Load Transient Load Transient (VIN=12V, VOUT=3.3V, ILOAD=0-1A) (VIN=12V, VOUT=3.3V, ILOAD=0.2-2A) ∆VOUT IL 100mV/div ∆VOUT 1A/div IL Time (2ms/div) 200mV/div 2A/div Time (2ms/div) Startup from Enable Shutdown from Enable (VIN=12V, VOUT=3.3V, ILOAD=2A) (VIN=12V, VOUT=3.3V, ILOAD=2A) EN 5V/div VOUT 2V/div EN 5V/div VOUT 2V/div VLX 10V/div VLX 10V/div IL 2A/div IL 2A/div Time (2ms/div) VIN VOUT Time (800µs/div) Startup from VIN Shutdown from VIN (VIN=12V, VOUT=3.3V, ILOAD=2A) (VIN=12V, VOUT=3.3V, ILOAD=2A) 10V/div VIN 2V/div VOUT 10V/div 2V/div VLX 10V/div VLX 10V/div IL 2A/div IL 2A/div Time (2ms/div) AN_SY8120I Rev0.9 © 2018 Silergy Corp. Time (2ms/div) Silergy Corp. Confidential- Prepared for Customer Use Only 6 All Rights Reserved. AN_SY8120I Short Circuit Protection Short Circuit Protection (VIN=12V, VOUT=3.3V, Open to Short) (VIN=12V, VOUT=3.3V, 2A to Short) VOUT 2V/div VOUT 2V/div IL 2A/div IL 2A/div Time (10ms/div) AN_SY8120I Rev0.9 © 2018 Silergy Corp. Time (10ms/div) Silergy Corp. Confidential- Prepared for Customer Use Only 7 All Rights Reserved. AN_SY8120I Operation The SY8120I is a high efficiency, 500kHz synchronous step-down DC/DC regulator capable of delivering up to 2A load current. It can operate over a wide input voltage range from 4.2V to 18V and integrate main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. The SY8120I adopts the instant PWM architecture to achieve fast transient responses for high step down applications and high efficiency at light loads. The SY8120I provides protection functions such as cycle by cycle current limiting and thermal shutdown protection. SY8120I will sense the output voltage conditions for the fault protection. Applications Information Because of the high integration in the SY8120I, the application circuit based on this regulator is rather simple. Only input capacitor CIN, output capacitor COUT, output inductor L and feedback resistors (RH and RL) need to be selected for the targeted applications specifications. Feedback Resistor Dividers RH and RL Choose RH and RL to program the proper output voltage. To minimize the power consumption under light loads, it is desirable to choose large resistance values for both RH and RL. A value of between 10kΩ and 1MΩ is highly recommended for both resistors. If VOUT is 3.3V, RH=100k is chosen, then using following equation, RL can be calculated to be 22.1k: 0.6V RL = RH VOUT − 0.6V minimize the loop area formed by CIN, and IN/GND pins. In this case, a 10µF low ESR ceramic capacitor is recommended. 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 a better grade ceramic capacitor with 16V rating and more than 10µF 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 SY8120I 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 + 3) Input Capacitor CIN The ripple current through input capacitor is calculated as： I CIN _ RMS = I OUT ⋅ D(1 − D) Place a typical X5R or a better grade ceramic capacitor really close to the IN and GND pins to minimize the potential noise problem. Care should be taken to AN_SY8120I Rev0.9 © 2018 Silergy Corp. VOUT (1 − VOUT /VIN, MAX ) FSW × IOUT, MAX × 40% 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