UNISONIC TECHNOLOGIES CO., LTD UD05121 LINEAR INTEGRATED CIRCUIT 1.2A 1.5MHZ SYNCHRONOUS BUCK CONVERTER DESCRIPTION The UTC UD05121 is a monolithic synchronous buck regulator with a built in internal power MOSFET. It achieves 1.2A continuous output current fix switching frequency with excellent load and line regulation. Current mode operation provides fast transient response and eases of loop stabilization. Fault condition protection includes cycle-by-cycle current limiting, output short circuit protection and thermal shutdown. In shutdown mode the regulator draws less than 1μA of supply current. Internal soft-start minimizes the inrush supply current at initial startup. The UTC UD05121 requires a minimum number of readily available standard external components. FEATURES * 2.5V~5.5V input voltage range * Up to 1.2A Output Current * 300/200mΩ Internal Power MOSFET Switch * Stable with Low ESR Output Ceramic Capacitors * Up to 95% Efficiency * Less than 1μA Shutdown Current * 1.5Mhz Switching Frequency * Thermal Shutdown Protection * Current limit and short circuit protections. * Output Adjustable from 0.6V to VIN * Build-in soft start function ORDERING INFORMATION Ordering Number UD05121G-AF5-R Package SOT-25 Packing Tape Reel MARKING www.unisonic.com.tw Copyright © 2016 Unisonic Technologies Co., Ltd 1 of 7 QW-R221-028.E UD05121 PIN CONFIGURATION FB VCC 5 4 1 2 3 EN GND SW PIN DESCRIPTION PIN NO. 1 2 3 4 5 LINEAR INTEGRATED CIRCUIT PIN NAME EN GND SW VCC FB DESCRIPTION Chip enable pin. Active high. Ground pin Switching pin VCC input pin Feedback pin BLOCK DIAGRAM VCC UVLO and POR EN + ISEN Reference And bias FB 0.6V softatart + EA - Thermal shutdown + - COMP + - ILimit P-switch PWM Control logic Driver SW OSCILLATOR GND UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 2 of 7 QW-R221-028.E UD05121 LINEAR INTEGRATED CIRCUIT ABSOLUTE MAXIMUM RATING (TA= 25°C, unless otherwise specified) PARAMETER SYMBOL RATINGS UNIT VCC Pin Voltage VIN -0.3~7 V SW Pin Voltage VSW -0.7 ~ VIN+0.3 V EN, FB Pins Voltage -0.3 ~ VIN+0.3 V Continuous Power Dissipation PD 370 mW Junction Temperature TJ -40~125 °C Storage Temperature TSTG -65~150 °C Notes: 1. Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. 2. Stresses exceed those ratings may damage the device. THERMAL CHARACTERISTICS PARAMETER SYMBOL RATINGS Junction to Ambient θJA 270 Junction to Case θJC 85 Note: θJA is measured with the PCB copper are of approximately 1 in2 (Multi-layer). UNIT °C/W °C/W ELECTRICAL CHARACTERISTICS (VIN=5V, VEN=5V, VOUT=1.8V, TA= 25°C) PARAMETER Input Voltage Input UVLO Input OVLO Quiescent Current Shutdown Current FB Pin Voltage FB Pin Current Load Regulation Load Regulation EN Pin Voltage High EN Pin Voltage Low EN Pin Leakage Current Switching Frequency Current Limit Switching Maximum Duty Minimum Duty P-Switch RDS(ON) N-Switch RDS(ON Low Side Discharger Thermal Shutdown Thermal Shutdown Protection hysteresis SYMBOL VIN UVLO OVLO ICCQ ISD VFB IFB IOUT=0A IOUT=0A VFB=1V VEN=0V MIN 2.5 1.8 0.588 0A<IOUT<1.2A 2.5A<VIN<5.5V VENH VENL Dmax Dmin RDS(ON)-P RDS(ON)-N TSD TSH 2.2 6.0 250 0.1 0.6 MAX 5.5 2.5 350 1 0.612 ±50 1.5 FOSC CL TYP 0.6 0.3 VEN=3V UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw TEST CONDITIONS VIN=3V, VFB=0.5V or VOUT=90%, Duty Cycle<35% 1.1 0.1 1.5 1.4 1.7 0.4 1 1.9 A 100 0 300 200 60 160 30 UNIT V V V μA μA V nA % %/V V V uA MHz % % mΩ mΩ Ω °C °C 3 of 7 QW-R221-028.E UD05121 LINEAR INTEGRATED CIRCUIT TYPICAL APPLICATION CIRCUIT L1 2.2uH VIN VCC VOUT SW 10uF 22P OFF ON EN GND R1 10uF FB R2 VOUT=0.6x(1+R1/R2) VOUT=VFB × (1+R1/R2), VFB = 0.6V, R2 suggest 60k~300kΩ UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 4 of 7 QW-R221-028.E UD05121 LINEAR INTEGRATED CIRCUIT FUNCTION DESCRIPTION Normal Operation The UD05121 uses a user adjustable frequency, current mode, synchronous step-down architecture with internal paver switch. During normal operation, the internal power switch is turned on each cycle when the oscillator sets the SR latch, and turned off when the comparator resets the SR latch. The peak inductor current at which comparator resets the SR latch is controlled by the output of error amplifier EA. While the high-side switch is off, the external schottky diode turns on until either the inductor current starts to reverse or the beginning of the next switching cycle. Setting the Output Voltage Application circuit item shows the basic application circuit with adjustable output version. The external resistor sets the output voltage according to the following equation: VOUT = VFB×(1+ R1 ), VFB = 0.6V, R2 suggest 60k ~ 300kΩ R2 Table 1. Resistor select for output voltage setting VOUT 1.0V 1.2V 1.5V 1.8V 2.5V 3.3V R1 100K 100K 150K 200K 470K 450K R2 150K 100K 100K 100K 150K 100K Dropout Operation As the input supply voltage decreases to a value approaching the output voltage, the duty cycle increases toward the maximum on-time. Further reduction of the supply voltage forces the high-side switch to remain on for more than one cycle until it reaches 100% duty cycle. The output voltage is dropped from the input supply for the voltage which across the high-side switch. Over Temperature Protection In most applications the UD05121 does not dissipate much heat due to high efficiency. But, in applications where the UD05121 is running at high ambient temperature with low supply voltage and high duty cycles, such as in dropout, the heat dissipated may exceed the maximum junction temperature of the part. If the junction temperature reaches approximately 160°C, the internal high-side power switch will be turned off and the LX node will become high impedance. Over Current Protection The UD05121 cycle-by-cycle limits the peak inductor current to protect embedded switch from damage. Hence the maximum output current (the average of inductor current) is also limited. In case the load increases, the inductor current is also increase. Whenever the current limit level is reached, the output voltage cannot be regulated and starting to drop. Soft-Start The UD05121 employs internal soft-start circuitry to reduce supply inrush current during startup conditions. When the device exits under-voltage lockout or shut-down mode, the soft-start circuitry will slowly ramp up the output voltage. Short-circuit Protection Short-circuit protection will activate once the feedback voltage falls below, and the operating frequency will be reducing normal switching frequency to reduce power delivered from input to output. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 5 of 7 QW-R221-028.E UD05121 LINEAR INTEGRATED CIRCUIT TYPICAL CHARACTERISTICS C1=100μF, C2=330μF, L1=33μH, TA=25°C Efficiency Test (VIN=5V) Efficiency, EFF (%) Efficiency, EFF (%) Efficiency Test (VOUT=1.0V) 100 90 80 70 60 50 40 30 20 10 0 5VIN 3.6VIN 2.7VIN 0.5 1.0 Output Current, IOUT (A) 0 1.5 Quiescent Current, ICCQ (mA) Switch Frequency, FOSC (MHz) 1.45 1.40 1.35 1.30 1.25 3.5 4.0 4.5 5.0 Input Voltage, VIN (V) VOUT=1V 0.5 0 1.5 1.0 Quiescent Current vs. Input Voltage Frequency vs. Input Voltage 3.0 60 50 40 30 20 10 0 Output Current, IOUT (A) 1.50 1.20 2.5 100 90 80 70 5.5 0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 2.5 VIN=5V, VOUT=1.0V, ILOAD=No Load 3.0 3.5 4.0 4.5 5.0 Input Voltage, VIN (V) 5.5 VIN=5V, VOUT=1.0V, IOUT=1.2A VIN SW VIN SW VOUT VOUT IOUT IOUT UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 6 of 7 QW-R221-028.E UD05121 LINEAR INTEGRATED CIRCUIT UTC assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all UTC products described or contained herein. UTC products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 7 of 7 QW-R221-028.E