UM3501 600mA, 1.2MHz, Synchronous Step-Down DC-DC Converter UM3501 SOT23-5 UM3501DA DFN6 2.0×2.0 General Description UM3501 is a high-efficiency pulse-width-modulated (PWM) step-down DC-DC converter, capable of delivering 600mA output current over a wide input voltage range from 2.5V to 5.5V. The target application of UM3501 is for portable electronic devices that are powered from 1-cell Li-ion battery or from other power sources within the range such as cellular phones, PDAs and handy-terminals. Internal synchronous rectifier with low RDS(ON) dramatically reduces conduction loss at PWM mode. No external schottky diode is required in practical application. The UM3501 automatically turns off the synchronous rectifier while the inductor current is low and enters discontinuous PWM mode. This can increase efficiency at light load condition. UM3501 enter shutdown mode and consumes less than 0.1uA when EN pin is pulled low. The operation frequency is set to 1.2MHz. This along with small SOT23-5 package and DFN6 2.0×2.0 package provides small PCB area application. Other features include lower internal reference voltage with 2% accuracy, over temperature protection, and over current protection. Applications Features Cellular and Smart Phones Microprocessors and DSP Core Supplies Wireless and DSL Modems PDAs, GPS MP3 Player Portable Instruments High Efficiency: Up to 90% 1.2MHz Constant Switching Frequency 600mA Output Current Integrated Main Switch and Synchronous Rectifier. No Schottky Diode Required 2.5V to 5.5V Input Voltage Range Low Quiescent Current: 50µA Thermal Fault Protection <1µA Shutdown Current Lead Free SOT23-5 Package and DFN6 2.0×2.0 Package Typical Application Circuit VIN L1 2.2uH SW VIN C1 4.7uF UM3501 R2 634K VOUT 1.8V C3 10uF FB EN GND R1 316K ________________________________________________________________________ http://www.union-ic.com Rev.06 Feb.2015 1/11 UM3501 Pin Configurations Top View 5 1 5 SW 5CA GND 2 1 EN M VIN 4 3 4 FB 2 3 UM3501 M: Month Code SOT23-5 NC 1 6 FB EN 2 5 GND VIN 3 4 SW AAE M (Top View) UM3501DA M: Month Code DFN6 2.0×2.0 Pin Description Pin Number SOT23-5 DFN6 2.0×2.0 Symbol 1 3 VIN 2 5 GND 3 2 EN 4 6 FB 5 4 SW - 1 NC Function Supply input pin. Must be closely decoupled to GND, Pin2, with a 4.7μF or greater ceramic capacitor. Ground. Regulator enable control input. Drive EN above 1.0V to turn on the part. Drive EN below 0.4V to turn it off. In shutdown, all functions are disabled drawing <1μA supply current. Do not leave EN floating. Feedback input pin. Connect FB to the center point of the external resistor divider. Power switch output. It is the switch node connection to Inductor. This pin connects to the drains of the internal P-CH and N-CH MOSFET switches. Not connected. Ordering Information Part Number Packaging Type Marking Code UM3501 SOT23-5 5CA UM3501DA DFN6 2.0×2.0 AAE Shipping Qty 3000pcs/7Inch Tape & Reel 3000pcs/7Inch Tape & Reel ________________________________________________________________________ http://www.union-ic.com Rev.06 Feb.2015 2/11 UM3501 Absolute Maximum Ratings (Note 1) Symbol Value Unit -0.3 to +6.0 V EN, FB Voltages -0.3 to VIN+0.3 V VSW SW Voltage -0.3 to VIN+0.3 V ISW Peak SW Sink and Source Current 1.5 A TO Operating Temperature -40 to +85 °C VIN VEN,VFB Parameter Input Voltage TSTG Storage Temperature Range -65 to +150 °C Note 1: Stresses greater than those listed under Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability. Electrical Characteristics (Note 2) (VIN=VEN=3.6V, TA=+25℃, unless otherwise noted) Symbol Parameter VIN Input Voltage Range IQ (Active) IQ (Shutdown) VFB Input DC Supply Current (Active Mode) Input DC Supply Current (Shutdown Mode) Regulated Feedback Voltage IO(max) FB Input Bias Current Reference Voltage Line Regulation Output Voltage Line Regulation Output Voltage Load Regulation Maximum Output Current f Oscillator Frequency RDS(ON) RDS(ON) of P-CH MOSFET RDS(ON) of N-CH MOSFET IFB IP Peak Inductor Current Test Conditions Min Typ 2.5 Max Unit 5.5 V μA 50 VFB=0.6V, Iload=0A VFB=0V, VIN=4.2V 0.08 1.0 TA= +25ºC 0.5880 0.6000 0.6120 0ºC ≤TA ≤ 85ºC 0.5865 0.6000 0.6135 -40ºC ≤TA ≤ 85ºC 0.5850 0.6000 0.6150 VFB=0.65V ±30 2.5V≤ VIN ≤ 5.5V, VOUT=VFB (R2=0) 2.5V≤ VIN ≤ 5.5V, IOUT=10mA 100mA≤IOUT≤600mA VIN=3.6V, VOUT=1.8V VFB=0.6V or VOUT=100% VIN =3.6V, ISW=100mA VIN =3.6, ISW= -100mA VIN=3.0V, VFB=0.5V or VOUT=90%, Duty Cycle<35% V nA 0.11 0.40 %/V 0.11 0.40 %/V 0.0015 %/mA 600 mA 1.2 0.90 μA MHz 0.40 0.50 Ω 0.35 0.45 Ω 1.20 1.90 A ________________________________________________________________________ http://www.union-ic.com Rev.06 Feb.2015 3/11 UM3501 Electrical Characteristics (continued) (VIN=VEN=3.6V, TA=+25℃, unless otherwise noted) Symbol ISWL VH VL IENL η(max) Parameter Test Conditions Min VEN=0V, VIN=5V ; VSW=0V or 5V SW Leakage EN High-Level Threshold EN Low-Level Threshold EN Leakage Current -40ºC ≤TA ≤ 85ºC Max. Efficiency Thermal Shutdown Temperature VIN=3.6V, VOUT=2.5V Typ Max Unit ±0.01 ±1 μA 1.0 V -40ºC ≤TA ≤ 85ºC ±0.1 0.4 V ±1 μA 90 % 160 ºC Note2: 100% production test at +25ºC. Specifications over the temperature range are guaranteed by design and characterization. Typical Performance Characteristics 100 100 90 90 80 80 70 70 Efficiency (%) Efficiency (%) (VIN = 3.6V, VOUT = 1.8V, L1= 2.2µH, C1= 4.7µF, C3= 10µF, TA = +25°C, unless otherwise noted.) Efficiency vs Load Current Efficiency vs Load Current 60 50 40 30 VOUT=1.8V 10 0 1 10 100 50 40 30 VIN=2.5V VIN=3.6V VIN=4.2V VIN=5.5V 20 60 20 VIN=3.6V 10 VOUT=1.2V VOUT=1.8V 0 1 1000 10 100 1000 Output Current (mA) Output Current (mA) Efficiency vs Input Voltage Output Voltage vs Load Current 100 1.81 90 1.80 Output Voltage(V) Efficiency (%) 80 70 60 50 40 30 20 10 VOUT=1.8V 0 2.5 3.5 ILOAD=200mA ILOAD=400mA ILOAD=600mA 4.5 Input Voltage (V) 1.79 1.78 1.77 VIN=2.5V VIN=3.6V VIN=4.2V 1.76 5.5 1.75 1 10 100 1000 Output Current (mA) ________________________________________________________________________ http://www.union-ic.com Rev.06 Feb.2015 4/11 UM3501 Typical Performance Characteristics (continued) (VIN = 3.6V, VOUT = 1.8V, L1= 2.2µH, C1= 4.7µF, C3= 10µF, TA = +25°C, unless otherwise noted.) Output Voltage vs Input Voltage Output Voltage vs Temperature 1.810 1.810 1.805 Output Voltage(V) 1.800 1.795 1.790 1.785 1.780 ILOAD=200mA ILOAD=400mA ILOAD=600mA 1.775 2.5 3.5 4.5 Input Voltage(V) 1.800 1.795 1.790 1.785 1.780 1.775 1.770 1.765 1.760 VIN=3.6V, Iload=100mA Iload=100mA 1.755 1.750 1.770 -50 5.5 -25 0 25 50 75 100 125 Temperature(℃) Supply Current vs Input Voltage Frequency vs Input Voltage 1600 80 70 1400 VOUT=1.8V 60 Frequency(kHz) Supply Current(uA) Output Voltage(V) 1.805 50 40 30 Iload=100mA 1200 1000 800 600 400 20 200 10 2.5 3 3.5 4 4.5 5 Supply Voltage(V) Line Transient Response (Vout=1.8V, Iout=300mA) VIN=3.5V to 4.5V VOUT 50mV/div 50μs/div 5.5 2.5 3 3.5 4 4.5 5 5.5 Supply Voltage(V) Load Transient Response (Vin=3.6V, Vout=1.8V) Iout=100mA to 600mA VOUT 100mV/div 50μs/div ________________________________________________________________________ http://www.union-ic.com Rev.06 Feb.2015 5/11 6 UM3501 Typical Performance Characteristics (continued) (VIN = 3.6V, VOUT = 1.8V, L1= 2.2µH, C1= 4.7µF, C3= 10µF, TA = +25°C, unless otherwise noted.) Light Load Operation (Vout=1.8V, Io=0mA) Heavy Load Operation (Vout=1.8V, Io=200mA) SW SW VOUT 20mV/div 5ms/div VOUT 20mV/div 500ns/div Block Diagram SLOPE COMP OSC VIN 2.5~5.5V VIN I SENSE AMP 1 + 0.6V FB + EA - _ S _ R Q _ Q RS LATCH PWM LOGIC NONOVERLAP CONTROL 4 ICOMP + DRV SW VOUT 5 R2 COUT VIN + - EN 3 REF 0.6V I ZERO COMP R1 2 GND Function Description UM3501 is a monolithic switching mode Step-Down DC-DC converter. It utilizes internal MOSFETs to achieve high efficiency and can generate very low output voltage by using internal reference at 0.6V. It operates at a fixed switching frequency, and uses the slope compensated current mode architecture. This Step-Down DC-DC Converter supplies 600mA output current at VIN =3.6V with input voltage range from 2.5V to 5.5V. ________________________________________________________________________ http://www.union-ic.com Rev.06 Feb.2015 6/11 UM3501 Current Mode PWM Control and Current Limit The UM3501 uses constant frequency, current mode step-down architecture. Both the main (P-channel MOSFET) and synchronous (N-channel MOSFET) switches are internal. From the block diagram, a comparator ICOMP is used to realize current limit protection. Lossless current sensing converts the peak current signal to a voltage to sum in with the internal slope compensation. This summed signal is compared to the error amplifier output to provide a peak current control command for the PWM. The cycle−by−cycle current limit is set at 1200mA (typical). During normal operation, the internal top power MOSFET is turned on each cycle when the oscillator sets the RS latch, and turned off when the current comparator ICOMP, resets the RS latch. The peak inductor current at which ICOMP resets the RS latch, is controlled by the output of error amplifier EA. When the load current increases, it causes a slight decrease in the feedback voltage, FB, relative to the 0.6V reference, which in turn, causes the EA amplifier’s output voltage to increase until the average inductor current matches the new load current. While the top MOSFET is off, the bottom MOSFET is turned on until either the inductor current starts to reverse, as indicated by the current reversal comparator IZERO, or the beginning of the next clock cycle. When the output is shorted to ground, the inductor current may exceed the maximum inductor peak current if not allowed enough time to decay. To prevent the inductor current from running away, the bottom N-channel MOSFET is allowed to stay on for more than one cycle, thereby allowing the inductor current time to decay. Pulse Skipping Mode Operation At very light loads, the UM3501 automatically enters Pulse Skipping Mode. In the Pulse Skipping Mode, the inductor current may reach zero or reverse on each pulse. The PWM control loop will automatically skip pulses to maintain output regulation. The bottom MOSFET is turned off by the current reversal comparator, IZERO, and the switch voltage will ring. This is discontinuous mode operation, and is normal behavior for the switching regulator. Maximum Load Current The UM3501 will operate with input supply voltage as low as 2.5V, however, the maximum load current decreases at lower input due to large IR drop on the main switch and synchronous rectifier. The slope compensation signal reduces the peak inductor current as a function of the duty cycle to prevent sub-harmonic oscillations at duty cycles greater than 50%. Conversely the current limit increases as the duty cycle decreases. Applications Information Output Voltage Setting The external resistor divider sets the output voltage.The feedback resistor R2 also sets the feedback loop bandwidth with the internal compensation capacitor. Choose R2 around 600kΩ for optimal transient response and feedback leakage current. R1 is then given by: R1 R2 VOU T 1 0.6V ________________________________________________________________________ http://www.union-ic.com Rev.06 Feb.2015 7/11 UM3501 Inductor Selection A 1µH to 10µH inductor with DC current rating at least 25% higher than the maximum load current is recommended for most applications. For best efficiency, the inductor DC resistance shall be<200mΩ. For most designs, the inductance value can be derived from the following equation: L VOUT (VIN VOUT ) VIN I L f OSC Where ∆IL is the inductor ripple current. Choose inductor ripple current approximately 30% of the maximum load current, 600mA. The maximum inductor peak current is: I L ( MAX) I LOAD I L 2 Under light load conditions below 100mA, larger inductance is recommended for improved efficiency. Input Capacitor Selection The input capacitor reduces the surge current drawn from the input and switching noise from the device. The input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current passing to the input. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. For most applications, a 4.7µF capacitor is sufficient. Output Capacitor Selection The output capacitor keeps output voltage ripple small and ensures regulation loop stable. The output capacitor impedance shall be low at the switching frequency. Ceramic capacitor with X5R or X7R dielectrics are recommended. The output ripple ∆VOUT is approximately: VOUT VOUT (VIN VOUT ) 1 ESR VIN f OSC L 8 f OSC C 3 Layout Guidance When laying out the PC board, the following suggestions should be taken to ensure proper operation of the UM3501. 1. The power traces, including the GND trace, the SW trace and the VIN trace should be kept short, direct and wide to allow large current flow. 2. Connect the input capacitor C1 to the VIN pin as closely as possible to get good power filter effect. 3. Keep the switching node, SW, away from the sensitive FB node. 4. Do not trace signal line under inductor. ________________________________________________________________________ http://www.union-ic.com Rev.06 Feb.2015 8/11 UM3501 Package Information UM3501: SOT23-5 Outline Drawing D b θ Symbol 5 E E1 4 2 3 L 1 e c 0.2 e1 A1 A End View A2 Top View Side View A A1 A2 b c D E E1 e e1 L θ DIMENSIONS MILLIMETERS Min Max 1.050 1.250 0.000 0.100 1.050 1.150 0.300 0.500 0.100 0.200 2.820 3.020 1.500 1.700 2.650 2.950 0.950REF 1.800 2.000 0.300 0.600 0° 8° INCHES Min Max 0.041 0.049 0.000 0.004 0.041 0.045 0.012 0.020 0.004 0.008 0.111 0.119 0.059 0.067 0.104 0.116 0.037REF 0.071 0.079 0.012 0.024 0° 8° Land Pattern 2.40 0.90 0.60 0.95 NOTES: 1. Compound dimension: 2.92×1.60; 2. Unit: mm; 3. General tolerance ±0.05mm unless otherwise specified; 4. The layout is just for reference. 0.95 5CA M Tape and Reel Orientation ________________________________________________________________________ http://www.union-ic.com Rev.06 Feb.2015 9/11 UM3501 UM3501DA: DFN6 2.0×2.0 A Outline drawing A3 A1 Side View D D2 D2/2 E2/2 L E E2 R 0.100 b e Symbol A A1 A3 b D E D2 E2 e L DIMENSIONS MILLIMETERS Min Typ 0.57 0.60 0 0.03 0.15TYP 0.20 0.25 1.95 2.00 1.95 2.00 1.45 1.55 0.76 0.86 0.65TYP 0.30 0.35 Max 0.63 0.05 0.30 2.075 2.075 1.65 0.96 0.40 Bottom View 0.65 1.00 1.20 2.50 Land Pattern 0.65 0.25 NOTES: 1. Compound dimension: 2.00×2.00; 2. Unit: mm; 3. General tolerance ±0.05mm unless otherwise specified; 4. The layout is just for reference. Tape and Reel Orientation AAE M ________________________________________________________________________ http://www.union-ic.com Rev.06 Feb.2015 10/11 UM3501 IMPORTANT NOTICE The information in this document has been carefully reviewed and is believed to be accurate. Nonetheless, this document is subject to change without notice. Union assumes no responsibility for any inaccuracies that may be contained in this document, and makes no commitment to update or to keep current the contained information, or to notify a person or organization of any update. Union reserves the right to make changes, at any time, in order to improve reliability, function or design and to attempt to supply the best product possible. Union Semiconductor, Inc Add: Unit 606, No.570 Shengxia Road, Shanghai 201210 Tel: 021-51093966 Fax: 021-51026018 Website: www.union-ic.com ________________________________________________________________________ http://www.union-ic.com Rev.06 Feb.2015 11/11