Preliminary Datasheet LP6252 High Efficiency 2.7A Synchronous Boost Convertor General Description Features The LP6252 is a Synchronous current mode boost Up to 95% efficiency DC-DC converter. Its PWM circuitry with built-in 2.7A Output to Input Disconnect at Shutdown Mode Current power MOSFET makes this converter highly Shut-down current:<1uA power efficiently. Selectable high switching frequency Output voltage Up to 5.5V allows faster loop response and easy filtering with a Over Output Voltage Protection low noise output. The non-inverting input its error Over Current Protection amplifier is connected to an internal 800mV precision Over Temperature Protection reference voltage. Current mode control and external Internal Compensation of Soft-start compensation network make it easy and flexible to 550KHz fixed frequency switching stabilize the system. High switch on current:2.7A Available in SOT23-6 and TDFN-6 Package Ordering Information LP6252 □ □ □ Pin Configurations TOP VIEW F: Pb-Free Package Type B6: SOT23-6 EN 1 6 FB OUT 2 5 GND VIN 3 4 LX 6 EN FB 1 GND 2 5 OUT GND QV: TDFN-6 4 VIN LX 3 SOT23-6 TDFN-6 Applications Battery products Host OTG Audio power Marking Information Device Marking Package Shipping LP6252B6F LPS SOT23-6 3K/REEL 5VYWX LP6252QVF LPS TDFN-6 5TYW Marking indication: Y:Production year W:Production period LP6252–00 Version 1.0 Aug.-2014 E-mail: [email protected] www.lowpowersemi.com X:Production batch Page 1 of 8 Preliminary Datasheet LP6252 Typical Application Circuit 4.7uH VIN LP6252 LX OUT 5V VIN 10uF 33pF/NC EN FB GND 68K 10uF*2 13K Functional Pin Description SOT23-6 TDFN-6 PIN Name Description Regulation Feedback Input. Connect to an external resistive 6 1 FB voltage divider from the output to FB to set the output voltage. The pin is 0.8V. 5 2 GND Ground Pin. 4 3 LX Pin for switching. 3 4 VIN Voltage supply input pin. 2 5 OUT Voltage output Pin. 1 6 EN Chip enable pin. LP6252 will turn on when EN=high, and turn off when EN=0. Function Block Diagram LX EN SLOPE COMPENSAION EN INTERNAL COMPENSATION CURRENT SENSER CURRENT LIMIT FB REF CONTROL LOGIC OSC VHIGH VIN BODY AND VHICH SELECT OUT GND LP6252–00 Version 1.0 Aug.-2014 E-mail: [email protected] www.lowpowersemi.com Page 2 of 8 Preliminary Datasheet LP6252 Absolute Maximum Ratings Supply Input Voltage---------------------------------------------------------------------------------------------------------------6V Power Dissipation, PD @ TA = 25°C Package Thermal Resistance SOT23-6, JA ---------------------------------------------------------------------------------------------------------------250°C/W TDFN-6, θja------------------------------------------------------------------------------------------------------------------95°C/W Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------------------------260°C Recommended Operating Conditions Supply Input Voltage---------------------------------------------------------------------------------------------------2.2V to 5.5V EN Input Voltage ----------------------------------------------------------------------------------------------------------0V to 5.5V Operation Junction Temperature Range ---------------------------------------------------------------- - −40°C to 125°C Operation Ambient Temperature Range--------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (Vin=3.5V,Vout=5V,Cin=10uF,Cout=22uF,L=4.7uH,R1=52.5K,R2=10K) Parameter Conditions LP6252 Min Typ Max Units Supply Voltage 2.2 5.5 V Output Voltage Range 2.5 5.5 V UVLO 1.4 2.0 V Over Output Voltage 5.4 6 V 0.05 1 uA 800 816 mV Protection Supply Current(Shutdown) VEN=0V,Vin=5V Feedback Voltage 784 Feedback Input Current VFB=0.8V Switching Frequency Maximum Duty Cycle 80 50 nA 550 KHz 90 EN Input Low Voltage EN Input High Voltage 1.4 Low-side Current Limit 2.7 High-side On Resistance Vout=3.3V Low-side On Resistance LP6252–00 Version 1.0 Aug.-2014 95 % 0.4 V V 3 A 110 70 E-mail: [email protected] www.lowpowersemi.com Page 3 of 8 Preliminary Datasheet LP6252 Typical Operating Characteristics Vout=5V Vin=3V Iout＝０ｍＡ Vout=5V Vin=3V Iout＝500ｍＡ Vout=5V Vin=3V Iout＝5０mA Vout=5V Vin=3V Iout＝1Ａ EN VS Vout LP6252–00 Version 1.0 Aug.-2014 E-mail: [email protected] www.lowpowersemi.com Page 4 of 8 Preliminary Datasheet LP6252 Operation Information The LP6252 uses a synchronous 550KHz fixed Set the output voltage by selecting the resistive frequency, current-mode regulation architecture to voltage divider ratio. The voltage divider drops the regulate the output voltage. The LP6252 measures the output voltage to the 0.8V feedback voltage. Use a output voltage through an external resistive voltage 100K resistor for R2 of the voltage divider. Determine divider and compares that to the internal 0.8V the high-side resistor R1 by the equation: reference to generate the error voltage to the inductor current to regulate the output voltage. The use of Vout=(R1/R2+1) x VFB current-mode regulation improves transient response and control loop stability. When the LP6252 is disable (EN=Low), both power switches are off. There is no current path from SW to OUT. Therefore, the output voltage discharges to ground. When the LP6252 is enabled(EN=High),a limited start-current charges the output voltage rising to SW, then the part operates in force PWM mode for regulating the output voltage to the target value. At the beginning of each cycle, the N-channel MOSFET switch is turned on, forcing the inductor current to rise, The current at the source of the switch is internally Pre-Boost Current and Short Circuit Protect Initially output voltage is lower than battery voltage, and the LP6252 enters pre-boost phase. During pre-boost phase, the internal NMOSFET/PMOSFET is turned off/on and a constant current is provided from battery to output until the output voltage close to the battery voltage. The constant current is limited by internal controller. If the output short to ground, the LP6252 also limits the output current to avoid damage condition measured and converted to a voltage by the current Inductor Selection sense amplifier. That voltage is compared to the error For a better efficiency in high switching frequency voltage. When the inductor current rises sufficiently, the PWM comparator turns off the switch, forcing the inductor current to the output capacitor through the converter, the inductor selection has to use a proper core material such as ferrite core to reduce the core loss and choose low ESR wire to reduce copper loss. internal P-Channel MOSFET rectifier, which forces the The most important point is to prevent the core inductor current to decrease. The peak inductor saturated when handling the maximum peak current. current is controlled by the error voltage. Thus the output voltage controls the inductor current to satisfy the lode. Using a shielded inductor can minimize radiated noise in sensitive applications. The maximum peak inductor current is the maximum input current plus the half of inductor ripple current. The calculated peak current has to be smaller than the current limitation in the electrical characteristics. A typical setting of the inductor ripple current is 20% to 40% of the maximum input current. If the selection is 40%, the maximum peak inductor current is Setting the Output Voltage LP6252–00 Version 1.0 Aug.-2014 E-mail: [email protected] www.lowpowersemi.com Page 5 of 8 Preliminary Datasheet LP6252 Output Capacitor Selection For lower output voltage ripple, low-ESR ceramic capacitors are recommended. The tantalum capacitors can be used as well, but the ESR is bigger than The minimum inductance value is derived from the ceramic capacitor. The output voltage ripple consists following equation : of two components: one is the pulsating output ripple current flows through the ESR, and the other is the capacitive ripple caused by charging and discharging. Depending on the application, the recommended inductor value is between 2.2μH to 4.7μH. Input Capacitor Selection For better input bypassing, low-ESR ceramic Layout Guide capacitors are recommended for performance. A 10μF For high frequency switching power supplies, the PCB input capacitor is sufficient for most applications. For a layout is important step in system application design. lower output power requirement application, this value In order to let IC achieve good regulation, high can be decreased. efficiency and stability, it is strongly recommended the power components should be placed as close as possible. The set races should be wide and short. The feedback pin and then works of feedback and compensation should keep away from the power loops, and be shielded with a ground trace or plane to prevent noise coupling. LP6252–00 Version 1.0 Aug.-2014 E-mail: [email protected] www.lowpowersemi.com Page 6 of 8 Preliminary Datasheet LP6252 Packaging Information LP6252–00 Version 1.0 Aug.-2014 E-mail: [email protected] www.lowpowersemi.com Page 7 of 8 Preliminary Datasheet LP6252–00 Version 1.0 Aug.-2014 E-mail: [email protected] www.lowpowersemi.com LP6252 Page 8 of 8