SY8077AAC

Application Notes: AN_SY8077 High Efficiency 1.5MHz, 1A Synchronous Step Down Regulator Preliminary Specification General Description Features SY8077 is a high efficiency 1.5MHz synchronous step down DC/DC regulator IC capable of delivering up to 1A output current. It can operate over a wide input voltage range from 2.5V to 6.5V and integrate main switch and synchronous switch with very low RDS (ON) to minimize the conduction loss. • Low RDS(ON) for internal switches (top/bottom) 260mΩ/170mΩ rth wo • High light load efficiency ky • Internal soft-start limits the inrush current rs SY8077 □(□□)□ Temperature Code Package Code Optional Spec Code • 100% dropout operation fo • RoHS Compliant and Halogen Free Note 1A ar ed • Compact package: SOT23-5 Applications tia l-P re p Package Type SOT23-5 • 40µA typical quiescent current • High switching frequency 1.5MHz minimizes the external components Ordering Information Ordering Number SY8077AAC • 2.5~6.5V input voltage range Portable Navigation Device Set Top Box USB Dongle Media Player Smart phone Efficiency vs. Load Current 93 88 er gy Efficiency (%) Co rp .C on Typical Application fid en • • • • • 83 78 Vin=6.5V Vout=1.8V Vin=5.0V Vout=1.8V 73 Vin=4.2V Vout=1.8V Sil Vin=3.3V Vout=1.8V 68 1 10 100 1000 Load Current (mA) Figure1. Schematic Diagram AN_SY8077 Rev. 0.1 Figure2. Efficiency Silergy Corp. Confidential- Prepared for Customer Use Only 1 AN_SY8077 rth Pinout (Top View) wo (SOT23-5) 5 rs FB Pin Description Enable control. Pull high to turn on. Do not float. Ground pin. Inductor pin. Connect this pin to the switching node of the inductor. Input pin. Decouple this pin to the GND pin with at least 10uF ceramic capacitor. 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).Add optional C1 (10pF~47pF) to speed up the transient response. fo Pin Number 1 2 3 4 tia l-P re p ar ed Pin Name EN GND LX IN ky Top Mark: TRxyz (device code: TR, x=year code, y=week code, z= lot number code) Absolute Maximum Ratings (Note 1) Co rp .C on fid en Supply Input Voltage -------------------------------------------------------------------------------------------------------- 7.0V Enable, FB Voltage---------------------------------------------------------------------------------------------------- VIN + 0.6V Power Dissipation, PD @ TA = 25°C, SOT23-5--------------------------------------------------------------------------- 0.6W Package Thermal Resistance (Note 2) θ JA -------------------------------------------------------------------------------------------------------------- 170°C/W θ JC ---------------------------------------------------------------------------------------------------------- ----130°C/W Junction Temperature Range ----------------------------------------------------------------------------------------------125°C Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------------------------- 260°C Storage Temperature Range ----------------------------------------------------------------------------------- -65°C to 150°C Recommended Operating Conditions (Note 3) Sil er gy Supply Input Voltage ----------------------------------------------------------------------------------------------- 2.5V to 6.5V Junction Temperature Range ----------------------------------------------------------------------------------- -40°C to 125°C Ambient Temperature Range ------------------------------------------------------------------------------------ -40°C to 85°C AN_SY8077 Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 2 AN_SY8077 Electrical Characteristics (VIN = 5V, VOUT = 2.5V, L = 2.2uH, COUT = 10uF, TA = 25°C, unless otherwise specified) 1 0.612 wo 170 1.3 1.5 Max 6.5 rth 40 0.1 0.6 260 0.588 tia l-P re p TSS TSD THYS Typ ky RDS(ON),N ILIM VENH VENL VUVLO VHYS FOSC IOUT=0, VFB=VREF ⋅ 105% EN=0 Min 2.5 rs NFET RON PFET Current Limit EN rising threshold EN falling threshold Input UVLO threshold UVLO hysteresis Oscillator Frequency Min ON Time Max Duty Cycle Soft Start Time Thermal Shutdown Temperature Thermal Shutdown Hysteresis Test Conditions fo Symbol VIN IQ ISHDN VREF RDS(ON),P ar ed Parameter Input Voltage Range Quiescent Current Shutdown Current Feedback Reference Voltage PFET RON 0.1 1.5 80 100 1 150 15 0.4 2.5 Unit V µA µA V mΩ mΩ A V V V V MHz ns % ms °C °C fid en Note 1: Stresses beyond the “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 for extended periods may remain possibility to affect device reliability. .C on 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. Exposed Paddle of DFN package is the case position for θ JC measurement. Sil er gy Co rp Note 3: The device is not guaranteed to function outside its operating conditions. AN_SY8077 Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 3 AN_SY8077 Typical Performance Characteristics Efficiency vs. Load Current Efficiency vs. Load Current 90 93 85 88 80 rth 83 75 78 Vin=6.5V Vout=1.2V 70 wo Vin=6.5V Vout=1.8V Vin=5.0V Vout=1.2V Vin=5.0V Vout=1.8V Vin=4.2V Vout=1.2V 73 Vin=4.2V Vout=1.8V ky 65 Vin=3.3V Vout=1.2V Vin=3.3V Vout=1.8V 60 1 10 100 1000 rs 68 1 10 100 1000 Load Current (mA) fo Load Current (mA) ar ed Efficiency vs. Load Current 98 tia l-P re p 95 92 89 86 83 Vin=6.5V Vout=3.3V 77 Vin=5.0V Vout=3.3V en 80 Output Ripple (VIN=5.0V, VOUT=1.8V, ILOAD=0A) ∆Vout 10mV/div LX 2.0V/div IL 0.2A/div 74 1 10 100 .C on 71 fid Vin=4.2V Vout=3.3V 1000 Time (400ns/div) Load Current (mA) Output Ripple ∆Vout 10mV/div 2.0V/div Sil er gy LX Co rp (VIN=5.0V, VOUT=1.8V, ILOAD=1.0A) IL 1A/div Time (400ns/div) AN_SY8077 Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 4 AN_SY8077 Startup from Enable Shutdown from Enable (VIN=5.0V, VOUT=1.8V, ILOAD=1.0A) (VIN=5.0V, VOUT=1.8V, ILOAD=1.0A) 5.0V/div EN 5.0V/div VOUT 1.0V/div VOUT 1.0V/div LX 5.0V/div LX 5.0V/div IL 1.0A/div rth EN 1.0A/div ky wo IL Time (40µs/div) Sil er gy Co rp .C on fid en tia l-P re p ar ed fo rs Time (400µs/div) AN_SY8077 Rev. 0.1 Silergy Corp. Confidential- Prepared for Customer Use Only 5 AN_SY8077 R1 = rth wo Short Circuit Protection: SY8077 integrates hic-cup mode hard short protection function. If output voltage is below 40% of the regulation voltage, the internal soft-start node and the error amplifier output will be reset immediately. IC works in hic-cup protection mode. The hiccup frequency is about 250Hz, and the hic-cup duty is 50%. If the hard short condition is removed, IC will go back to normal operation. tia l-P re p 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 100kΩ and 1MΩ is highly recommended for both resistors. If R2=120kΩ is chosen, then R1 can be calculated to be: ky Because of the high integration in the SY8077 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. rs Applications Information fo The SY8077 is a high-efficiency 1.5MHz synchronous step-down DC-DC converters capable of delivering up to 1A output current. It operates over a wide input voltage range from 2.5V to 6.5V and integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. where Fsw is the switching frequency and Iout,max is the maximum load current. The SY8077 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(1-VOUT/VIN,MAX) ISAT, MIN > IOUT, MAX + 2 ⋅ FSW ⋅ L 3) 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