LC2202CB5TR

LC2202 2A 2MHz 5.5V Synchronous Buck Converter DESCRIPTION FEATURES The LC2202 is a high-efficiency, DC-to-DC stepdown switching regulators, capable of delivering up to 2A of output current. The device operates from an input voltage range of 2.6V to 5.5V and provides an output voltage from 0.6V to VIN. Working at a fixed frequency of 2MHz allows the use of small external components, such as ceramic input and output caps, as well as small inductors, while still providing low output ripples. This low noise output along with its excellent efficiency achieved by the internal synchronous rectifier, making LC2202 an ideal replacement for large power consuming linear regulators. Internal soft-start control circuitry reduces inrush current. Short-circuit and thermal shutdown protection improves design reliability.           The LC2202 is available in SOT23-5 package. TYPICAL APPLICATION VIN 2.6V to 5.5V 10uF VOUT 1.8V SW LC2202 EN 240k        Cellular phones Digital cameras MP3 and MP4 players Set top boxes Wireless and DSL modems USB supplied devices in notebooks Portable devices FB VIN 5 4 option NC FB GND APPLICATIONS PIN OUT & MARKING 1uH/2.2uH VIN High efficiency: up to 97% Up to 2A Max output current 2MHz switching frequency Low dropout 100% duty operation Internal compensation and soft-start Current mode control Reference 0.6V Logic control shutdown (IQ2000V Note: Exceed these limits to damage to the device. Exposure to absolute maximum rating conditions may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN=5V, TA=25C, unless otherwise specified.) Symbol Parameter VIN Input voltage range VOVP Input overvoltage threshold VREF Feedback voltage Conditions 0.588 IQ Quiescent current Active, VFB=0.65, No Switching Shutdown input current EN=0V LNR Line regulation Vin=2.6V to 5.5V LDR Load regulation Iout=0.01 to 1A FSOC Switching frequency PMOS Rdson RDSON_N NMOS Rdson VUVLO VUVLO_HY ILIMIT V 0.1 1 uA 1.9 uA 0.1 0.2 %/V 0.1 0.2 %/A 2 2.4 MHz 180 250 mohm 130 200 mohm 2.1 2.3 V 2.7 Vin=5V, Vout=3.3V, Iout=0A EN leakage current VH_EN EN input high voltage VL_EN EN input low voltage uA 1 Peak current limit IENLK V 0.612 100 SW leakage current V 0.6 UVLO hysteresis ISWLK Unit 5.5 80 1.6 Under voltage lockout INOLOAD Max 6.1 Vin=5V Feedback leakage current RDSON_P Typ 2.6 IFB ISHUTDOWN Min mV 3.3 80 Vin=6V, VSW=0 or 6V, EN=0V A uA 1 uA 1 uA 1.2 V 0.5 V TSD Thermal shutdown temp 160 °C TSH Thermal shutdown hysteresis 15 °C www.leadchip.com.cn 2 Your final power solution LC2202 ELECTRICAL PERFORMANCE Tested under TA=25C, unless otherwise specified Efficiency vs. Output Current Efficiency vs. Output Current (Vout=3.3V) 100% 100% 95% 95% 90% 90% 85% 85% Efficiency Efficiency (Vout=1.8V) 80% 75% 80% 75% 70% 70% 65% 65% 60% 60% 55% 55% Vin=5V 50% 0.001 0.01 0.1 Iout (A) 1 Vin=5V 50% 0.001 10 Load Regulation 0.01 1 10 Load Regulation (Vout=1.8V) (Vout=3.3V) 2.0 3.5 1.9 3.4 1.8 3.3 Vout(V) Vout(V) 0.1 Iout (A) 1.7 1.6 3.2 3.1 Vin=5V Vin=5V 1.5 3.0 0.0 0.5 1.0 Iout (A) 1.5 2.0 0.0 0.5 1.0 Iout (A) 1.5 Output Ripple and SW at 1A load Output Ripple and SW at 1A load Vin=5V / Vout=1.8V Ch2—Vout ripple, Ch3—Vsw, Ch4—ISW Vin=5V / Vout=3.3V Ch2—Vout ripple, Ch3—Vsw, Ch4—ISW Vout ripple, 20mV/div Vout ripple, 20mV/div Vsw, 2V/div Vsw, 2V/div Isw, 1A/div Isw, 1A/div www.leadchip.com.cn 3 2.0 Your final power solution LC2202 Load Transient Load Transient Vin=5V / Vout=1.2V / Iout=0.01~1.5A Ch2—Vout ripple, Ch4—Iout Vin=5V / Vout=3.3V / Iout=0.01~1.5A Ch2—Vout ripple, Ch4—Iout Vout ripple, 100mV/div Vout ripple, 200mV/div Iout, 500mA/div Iout, 500mA/div PIN DESCRIPTION PIN # NAME DESCRIPTION 1 2 3 4 EN GND SW VIN 5 FB Enable pin for the IC. Drive the pin to high to enable the part, and low to disable Ground Inductor connection. Connect an inductor between SW and the regulator output. Supply voltage. Feedback input. Connect an external resistor divider from the output to FB and GND to set the output to a voltage between 0.6V and Vin BLOCK DIAGRAM www.leadchip.com.cn 4 Your final power solution LC2202 DETAILED DESCRIPTION The LC2202 high-efficiency switching regulator is a small, simple, DC-to-DC step-down converter capable of delivering up to 2A of output current. The device operates in pulse-width modulation (PWM) at 2MHz from a 2.6V to 5.5V input voltage and provides an output voltage from 0.6V to VIN, making the LC2202 ideal for on-board postregulation applications. An internal synchronous rectifier improves efficiency and eliminates the typical Schottky free-wheeling diode. Using the on resistance of the internal high-side MOSFET to sense switching currents eliminates current-sense resistors, further improving efficiency and cost. the error amplifier output by the PWM comparator to terminate the on cycle. Current limit There is a cycle-by-cycle current limit on the highside MOSFET of 2.7A (typ). When the current flowing out of SW exceeds this limit, the high-side MOSFET turns off and the synchronous rectifier turns on. LC2202 utilizes a frequency fold-back mode to prevent overheating during short-circuit output conditions. The device enters frequency fold-back mode when the FB voltage drops below 100mV, limiting the current to 2.7A (typ) and reducing power dissipation. Normal operation resumes upon removal of the short-circuit condition. Loop operation LC2202 uses a PWM current-mode control scheme. An open-loop comparator compares the integrated voltage-feedback signal against the sum of the amplified current-sense signal and the slope compensation ramp. At each rising edge of the internal clock, the internal high-side MOSFET turns on until the PWM comparator terminates the on cycle. During this on-time, current ramps up through the inductor, sourcing current to the output and storing energy in the inductor. The current mode feedback system regulates the peak inductor current as a function of the output voltage error signal. During the off cycle, the internal highside P-channel MOSFET turns off, and the internal low-side N-channel MOSFET turns on. The inductor releases the stored energy as its current ramps down while still providing current to the output. Soft-start LC2202 has an internal soft-start circuitry to reduce supply inrush current during startup conditions. When the device exits under-voltage lockout (UVLO), shutdown mode, or restarts following a thermal shutdown event, the soft-start circuitry slowly ramps up current available at SW. UVLO If VIN drops below 2.1V, the UVLO circuit inhibits switching. Once VIN rises above 2.2V, the UVLO clears, and the soft-start sequence activates. Thermal shutdown Thermal shutdown protection limits total power dissipation in the device. When the junction temperature exceeds TJ= +160°C, a thermal sensor forces the device into shutdown, allowing the die to cool. The thermal sensor turns the device on again after the junction temperature cools by 15°C, resulting in a pulsed output during continuous overload conditions. Following a thermal-shutdown condition, the soft-start sequence begins. Current sense An internal current-sense amplifier senses the current through the high-side MOSFET during on time and produces a proportional current signal, which is used to sum with the slope compensation signal. The summed signal then is compared with DESIGN PROCEDURE Setting output voltages Input capacitor selection Output voltages are set by external resistors. The FB threshold is 0.6V. The input capacitor in a DC-to-DC converter reduces current peaks drawn from the battery or other input power source and reduces switching noise in the controller. The impedance of the input capacitor at the switching frequency should be less ( www.leadchip.com.cn ) 5 Your final power solution LC2202 than that of the input source so high-frequency switching currents do not pass through the input source. The output capacitor keeps output ripple small and ensures control-loop stability. The output capacitor must also have low impedance at the switching frequency. Ceramic, polymer, and tantalum capacitors are suitable, with ceramic exhibiting the lowest ESR and high-frequency impedance. Output ripple with a ceramic output capacitor is approximately as follows: ( ) ( ) If the capacitor has significant ESR, the output ripple component due to capacitor ESR is as follows: ( ) LAYOUT GUIDE The blue line is placed on the back side. Cout as close as possible to Vout Cout Vout L GND FB&GND connected to R1 directly as short as possible Keep the path short and wide for low resistance www.leadchip.com.cn FB VIN Make GND loop Resistance as small as possible SW SW Jumper Off EN On GND Keep the path short and wide for low resistance VIN Cin 6 R1 R2 Cin as close as possible to VIN Your final power solution LC2202 PACKAGE OUTLINE Package SOT23-5 Devices per reel 3000 Unit mm Package specification： www.leadchip.com.cn 7 Your final power solution