UM3500 600mA, 1.5MHz, Synchronous Step-Down DC-DC Converter UM3500 SOT23-5 General Description The UM3500 is a 1.5MHz constant frequency, slope compensated current mode PWM step-down converter. The device integrates a main switch and a synchronous rectifier for high efficiency without an external Schottky diode. It is ideal for powering portable equipment that runs from a single cell lithium-Ion (Li+) battery. The UM3500 can supply 600mA of load current from a 2.5V to 5.5V input voltage. The output voltage can be regulated as low as 0.6V. The UM3500 can also run at 100% duty cycle for low dropout operation, extending battery life in portable system. Pulse Skipping Mode operation at light loads provides very low output ripple voltage for noise sensitive applications. The UM3500 is available in a low profile SOT23-5 package. Applications Features Cellular and Smart Phones Microprocessors and DSP Core Supplies Wireless and DSL Modems PDAs, GPS MP3 Player Portable Instruments Pin Configurations High Efficiency: Up to 96% 1.5MHz Constant Switching Frequency 600mA Output Current Integrated Main Switch and Synchronous Rectifier. No External Schottky Diode. 2.5V to 5.5V Input Voltage Range Output Voltage as Low as 0.6V 100% Duty Cycle in Dropout Low Quiescent Current: 50µA Short Circuit Protection Thermal Fault Protection <1µA Shutdown Current Lead Free SOT23-5 Package Top View WW: Week Code UM3500 SOT23-5 ________________________________________________________________________ http://www.union-ic.com Rev.04 May.2016 1/11 UM3500 Ordering Information Part Number Packaging Type Marking Code UM3500 SOT23-5 LTA5 Shipping Qty 3000pcs/7Inch Tape & Reel Pin Description Pin Number Symbol 1 RUN 2 GND 3 SW 4 VIN 5 VFB Function Regulator enables control input. Drive RUN above 1.0V to turn on the part. Drive RUN below 0.4V to turn it off. In shutdown, all functions are disabled drawing <1μA supply current. Do not leave RUN floating. Ground. 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. Supply input pin. Must be closely decoupled to GND, Pin 2, with a 2.2μF or greater ceramic capacitor. Feedback input pin. Connect FB to the center point of the external resistor divider. Bonding option Absolute Maximum Ratings (Note 1) Symbol VIN Parameter Input Voltage Value Unit -0.3 to +6.0 V VRUN,VFB RUN, VFB Voltages +0.3 to VIN+0.3 V VSW,VOUT SW, VOUT Voltages +0.3 to VIN+0.3 V 1.5 A ISW Peak SW Sink and Source Current TO Operating Temperature -40 to +85 °C Storage Temperature Range -65 to +150 °C TSTG 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. ________________________________________________________________________ http://www.union-ic.com Rev.04 May.2016 2/11 UM3500 Electrical Characteristics (Note 2) (VIN=VRUN=3.6V, TA=+25°C, unless otherwise noted) Symbol Parameter VIN Input Voltage Range Input DC Supply Current (Active Mode) Input DC Supply Current (Shutdown Mode) IQ (Active) IQ (Shutdown) VFB Regulated Feedback Voltage IFB VFB Input Bias Current Reference Voltage Line Regulation IO(Max) 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 IP Peak Inductor Current ISWL SW Leakage IRUNL RUN High-Level Threshold RUN Low-Level Threshold RUN Leakage Current η(MAX) Max. Efficiency VH VL Thermal Shutdown Temp Test Conditions Min Typ 2.5 Max Unit 5.5 V VFB=3.6V, VFB=VREF+5% 50 100 μA VFB=0V, VIN=4.2V 0.08 1.0 μA 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 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% VRUN=0V, VSW=0V or 5V VIN=5V -40ºC≤TA≤85ºC ±30 nA 0.11 0.40 %/V 0.11 0.40 %/V 0.0015 mA 1.5 1.8 MHz 0.40 0.50 Ω 0.35 0.45 Ω 1.20 ±0.01 A ±1 1.0 μA V -40ºC≤TA≤85ºC VRUN=3.6V VIN=2.7V, VOUT=2.5V %/mA 600 1.2 V 2.0 90 0.4 V 3.5 μA % 160 ºC Note2: 100% production test at +25ºC. Specifications over the temperature range are guaranteed by design and characterization. ________________________________________________________________________ http://www.union-ic.com Rev.04 May.2016 3/11 UM3500 Block Diagram Typical Application Circuit ________________________________________________________________________ http://www.union-ic.com Rev.04 May.2016 4/11 UM3500 Function Description UM3500 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. Current Mode PWM Control Slope compensated current mode PWM control provides stable switching and cycle by cycle current limit for excellent load and line responses. During normal operation, the internal main switch is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and turned off when the peak inductor current reaches the controlled value. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current starts to reverse, as indicated by the current reversal comparator, IRCMP, or the beginning of the next clock cycle. Pulse Skipping Mode Operation At very light loads, the UM3500 will automatically enter Pulse Skipping Mode to increase efficiency, further extending battery life. In this mode, the control loop skips PWM pulses while maintaining output in regulation, and the switching frequency depends on the load condition. This is a kind of PFM mode operation. Dropout Operation When the input voltage decreases toward the value of the output voltage, the UM3500 allows the main switch to remain on for more than one switching cycle and increases the duty cycle (Note 1) until it reaches 100%. The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. At low input supply voltage, the RDS(ON) of the P-Channel MOSFET increases, and the efficiency of the converter decreases. Caution must be exercised to ensure the heat dissipated not to exceed the maximum junction temperature of the IC. Note 1: The duty cycle D of a step-down converter is defined as: D=TON×fOSC×100%≌VOUT/VIN×100% Where TON is the main switch on time and fOSC is the oscillator frequency (1.5MHz). Maximum Load Current The UM3500 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. ________________________________________________________________________ http://www.union-ic.com Rev.04 May.2016 5/11 UM3500 Typical Performance Characteristics ( L1=2.2µH, C1=4.7µF, C3=10µF, TA=+25°C, unless otherwise noted.) Efficiencyvsvs. Load Current Efficiency Load Current 90 90 80 80 70 70 60 50 40 30 VIN=2.7V VIN=3.6V VIN=4.2V 20 10 0 0.1 1 10 100 Efficiency vs vs.Load LoadCurrent Current Efficiency 100 Efficiency(%) Efficiency(%) 100 60 50 40 30 VIN=2.7V VIN=3.6V VIN=4.2V 20 10 0 0.1 1000 1 Efficiencyvs vs.Load LoadCurrent Current Efficiency 2.2 90 2.1 80 2.0 Output Voltage(V) 100 Efficiency(%) 70 60 50 40 VIN=2.7V VIN=3.6V VIN=4.2V 20 10 1 10 1000 100 OutputVoltage Voltage vs vs.Load LoadCurrent Current Output VIN=3.6V 1.9 1.8 1.7 1.6 1.5 1.4 1.3 0 0.1 100 Load Current(mA) Load Current(mA) 30 10 1000 0 200 400 600 800 1000 1200 Load Current(mA) Load Current(mA) Output Voltagevsvs. Supply Voltage Output Voltage Supply Voltage 1.800 1.820 Output Voltage Temperature Output Voltage vsvs. Temperature 1.798 1.815 VIN=3.6V 1.810 IO=600mA Output Voltage(V) Output Voltage(V) 1.796 1.805 1.800 IO=100mA 1.795 1.790 IO=10mA 1.792 1.790 1.788 1.786 1.784 1.782 1.785 1.780 2.0 1.794 2.5 3.0 3.5 4.0 4.5 5.0 Supply Voltage(V) 5.5 6.0 1.780 -50 -25 0 25 50 75 100 125 o Temperature( C) ________________________________________________________________________ http://www.union-ic.com Rev.04 May.2016 6/11 UM3500 Typical Performance Characteristics (Continued) ( L1=2.2µH, C1=4.7µF, C3=10µF, TA= +25°C, unless otherwise noted.) Run Current Current vs. vs Run Run RunVoltage Voltage LoadTransient Transient Load 4.0 3.5 VOUT=1.8V,IO=0mA IRUN(uA) 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VRUN (V) Start-up from Shutdown Short-Circuit Protection ________________________________________________________________________ http://www.union-ic.com Rev.04 May.2016 7/11 UM3500 Applications Information Output Voltage Setting The external resistor divider sets the output voltage.The feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor. Choose R1 around 300kΩ for optimal transient response. R2 is then given by: R2 R1 VO UT 1 0.6V 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 C 3 OSC ________________________________________________________________________ http://www.union-ic.com Rev.04 May.2016 8/11 UM3500 Layout Guidance When laying out the PC board, the following suggestions should be taken to ensure proper operation of theUM3500. 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. Put enough multiply-layer pads when they need to change the trace layer. 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.04 May.2016 9/11 UM3500 Package Information UM3500: SOT23-5 Outline Drawing θ D b L Symbol 4 E E1 5 1 2 3 e1 c Top View End View A1 A2 A e Side View A A1 A2 b c D E E1 e e1 L θ DIMENSIONS MILLIMETERS INCHES Min Typ Max Min Typ Max 1.013 1.15 1.40 0.040 0.045 0.055 0.00 0.05 0.10 0.000 0.002 0.004 1.00 1.10 1.30 0.039 0.043 0.051 0.30 0.50 0.012 0.020 0.10 0.15 0.20 0.004 0.006 0.008 2.82 3.10 0.111 0.122 1.50 1.60 1.70 0.059 0.063 0.067 2.60 2.80 3.00 0.102 0.110 0.118 0.95REF 0.037REF 1.90REF 0.075REF 0.30 0.60 0.012 0.024 0° 8° 0° 8° Land Pattern 2.35 0.56 1.20 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 0.95 Tape and Reel Orientation LTA5 WW ________________________________________________________________________ http://www.union-ic.com Rev.04 May.2016 10/11 UM3500 GREEN COMPLIANCE Union Semiconductor is committed to environmental excellence in all aspects of its operations including meeting or exceeding regulatory requirements with respect to the use of hazardous substances. Numerous successful programs have been implemented to reduce the use of hazardous substances and/or emissions. All Union components are compliant with the RoHS directive, which helps to support customers in their compliance with environmental directives. For more green compliance information, please visit: http://www.union-ic.com/index.aspx?cat_code=RoHSDeclaration 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.04 May.2016 11/11