CM3706 1.5MHz, 600mA Synchronous Step-Down Regulator GENERAL DESCRIPTION FEATURES The CM3706 is a 1.5MHz constant frequency, slope ◆ High Efficiency: Up to 96% compensated current mode PWM step-down converter. ◆ 1.5Mhz Constant Switching Frequency The device integrates a main switch and a synchronous ◆ 600mA Output Current at VIN=3V rectifier for high efficiency without an external Schottky ◆ Integrated Main switch and synchronous rectifier. No diode. It is ideal for powering portable equipment that runs Schottky Diode Required from a single cell lithium-Ion (Li+) battery. The CM3706 ◆ 2.5V to 5.5V Input Voltage Range can supply 600mA of load current from a 2.5V to 5.5V ◆ Output Voltage as Low as 0.6V input voltage. The output voltage can be regulated as ◆ 100% Duty Cycle in Dropout low as 0.6V. The CM3706 can also run at 100% duty cycle ◆ Low Quiescent Current: 300µA for low dropout operation, extending battery life in portable ◆ Slope Compensated Current Mode Control for Excellent Line system. Idle mode operation at light loads provides very and Load Transient Response low output ripple voltage for noise sensitive applications. ◆ Short Circuit Protection The CM3706 is offered in a low profile (1mm) 5-pin, thin ◆ Thermal Fault Protection TSOT package, and is available in an adjustable version. ◆ <1uA Shutdown Current ◆ Space Saving 5-Pin Thin TSOT23 package APPLICATIONS Cellular and Smart Phones MP3 Players Microprocessors and DSP Core Supplies Portable Instruments Wireless and DSL Modems Digital Still and Video Cameras PDAs TYPICAL APPLICATIONS 4 IN 3 VIN 2.5V TO 5.5V Cin 4.7uF 1 2.2uH OUT SW CM3706 RUN GND V FB 2 634k 5 316K Cout 10uF 22PF Figure 1. Basic Application Circuit with CM3706 adjustable version 2006/12/20Rev. 1.6 Champion Microelectronic Corporation Page 1 CM3706 1.5MHz, 600mA Synchronous Step-Down Regulator PIN CONFIGURATION TSOT23-5 Top View 4 RUN GND SW VIN FB 5 1 2 3 BLOCK DIAGRAM 2006/12/20Rev. 1.6 Champion Microelectronic Corporation Page 2 CM3706 1.5MHz, 600mA Synchronous Step-Down Regulator PIN DESCRIPTION Pin No. 1 Symbol RUN Description Regulator Enable control input. Drive RUN above 1.5V to turn on the part. Drive RUN below 0.3V to turn it off. In shutdown, all functions are disabled drawing <1µA supply current. Do not leave RUN floating. 2 GND Ground Pin. 3 SW Power Switch Output. It is the Switch note connection to Inductor. This pin connects to the drains of the internal P-CH and N-CH MOSFET switches. 4 VIN Supply Input Pin. Must be closely decoupled to GND, Pin 2, with a 2.2µF or greater ceramic capacitor. 5 FB VFB (CM3706): Feedback Input Pin. Connect FB to the center point of the external resistor divider. The feedback threshold voltage is 0.6V. ORDERING INFORMATION Part Number Voltage Temperature Range Package CM3706IM25 Adj -40℃ to +85℃ TSOT23-5 CM3706GIM25 Adj -40℃ to +85℃ TSOT23-5 CM3706 Lead Free Blank : Normal G: Lead Free Package X X X Suffix for Temperature I : -40℃ to +85℃ Package M25 : TSOT23-5 ABSOLUTE MAXIMUM RATINGS(Note 1) Absolute maximum ratings are those values beyond which the device could be permanently damaged. Input Supply Voltage...................................................–0.3V to 6.0V Peak SW Sink and Source Current………...…………….. 1.5A RUN, VFB Voltages ………………………...…– 0.3V to (VIN + 0.3V) Junction Temperature (Note 2) ........... ........................ 125°C SW Voltage....…………........………..……..… – 0.3V to (VIN + 0.3V) Storage Temperature Range ....................... – 65°C to 150°C Operating Temperature Range….…………..…-40°C to +85°C Lead Temperature (Soldering, 10 sec)......................... 300°C OPERATING CONDITIONS Temperature Range ............................. -40°C to 85°C Vin Operating Range .........................2.5V to 5.5V 2006/12/20Rev. 1.6 Champion Microelectronic Corporation Page 3 CM3706 1.5MHz, 600mA Synchronous Step-Down Regulator Thermal Resistance (Note 3): Package TSOT23-5 ӨJA 250°C/W ӨJC 110°C/W Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: CM3706: TJ = TA + (PD)╳(ӨJA) Note 3: Thermal Resistance is specified with approximately 1 square of 1 oz copper. ELECTRICAL CHARACTERISTICS (Unless otherwise stated, these specifications apply TA=25°C; VIN=+3.6V) maximum ratings are stress ratings only and functional device operation is not implied. Parameter Input Voltage Range Input DC Supply Current Active Mode Shutdown Mode Conditions VFB=0.5V VFB = 0.65V Reference Voltage Line Regulation VIN = 2.5V to 5.5V, CM3706-1.2, -40°C ≤ TA ≤ 85°C CM3706-1.5, -40°C ≤ TA ≤ 85°C CM3706-1.8, -40°C ≤ TA ≤ 85°C 0.5880 0.5865 0.5850 1.164 1.455 1.746 VIN = 2.5V to 5.5V,IOUT=10mA IOUT from 10 to 600mA Oscillator Frequency RDS(ON) of P-CH MOSFET VIN=3V, VFB=0.5V or VOUT=90% Duty Cycle <35% VFB=0.6V or VOUT=100% ISW = 300mA RDS(ON) of N-CH MOSFET ISW = -300mA SW Leakage VRUN = 0V, VSW= 0V or 5V, VIN = 5V RUN Threshold RUN Leakage Current Thermal Shutdown Trip Threshold Output over voltage lockout -40°C ≤ TA ≤ 85°C Peak Inductor Current 270 VFB=0V, VIN=4.2V VFB Input Bias Current Output Voltage Line Regulation Output Voltage Load Regulation TYP 2.5 TA = +25°C Regulated Feedback Voltage TA= 0°C ≤ TA ≤ 85°C TA= -40°C ≤ TA ≤ 85°C Regulated Output Voltage MIN ∆VOVL = VOVL – VFB 1.2 0.3 MAX unit 5.5 V 400 µA 0.08 1.0 µA 0.6000 0.6000 0.6000 0.6120 0.6135 0.6150 V V V ±30 nA 0.11 0.4 %/V 1.200 1.500 1.800 1.236 1.545 1.854 V V V 0.11 0.40 %/V 0.0015 %/mA 1.2 A 1.5 0.3 1.8 0.50 MHz Ω 0.2 0.45 Ω ±0.01 ±1 µA 0.45 ±0.1 1.5 ±1 V µA 150 ℃ 60 mV Note 4: 100% production test at +25°C. Specifications over the temperature range are guaranteed by design and characterization. 2006/12/20Rev. 1.6 Champion Microelectronic Corporation Page 4 CM3706 1.5MHz, 600mA Synchronous Step-Down Regulator FUNCTIONAL DESCRIPTION Operation Idle Mode Operation CM3706 is a monolithic switching mode Step-Down DC-DC At very light loads, the CM3706 automatically enters Idle converter. It utilizes internal MOSFETs to achieve high Mode. In the Idle Mode, the inductor current may reach zero efficiency and can generate very low output voltage by using or reverse on each pulse. internal reference at 0.6V. It operates at a fixed switching automatically skip pulses to frequency, and uses the slope compensated current mode maintain output regulation. The bottom MOSFET is turned architecture. This Step-Down DC-DC Converter supplies off by the current reversal comparator, IZERO, and the switch 600mA output current at VIN = 3V with input voltage range voltage will ring. This is discontinuous mode operation, and from 2.5V to 5.5V. is normal behavior for the switching regulator. Current Mode PWM Control Maximum Load Current The CM3706 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. Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for excellent load and line responses and protection of the internal main switch (P-Ch MOSFET) and synchronous rectifier (N-CH MOSFET). During normal operation, the internal P-Ch MOSFET is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. The current comparator, ICOMP, The PWM control loop will limits the peak inductor current. When the main switch is off, the Note 5: The duty cycle D of a step-down converter is defined synchronous rectifier will be turned on immediately and stay as: on until either the inductor current starts to reverse, as D = TON × f OSC × 100% ≈ indicated by the current reversal comparator, IZERO, or the beginning of the next clock cycle. The OVDET comparator controls output transient overshoots by turning the main switch off and keeping it off until the fault is no longer present. V OUT ×100% VIN where TON is the main switch on time, and fOSC is the oscillator frequency (1.5Mhz). Dropout Operation When the input voltage decreases toward the value of the output voltage, the CM3706 allows the main switch to remain on for more than one switching cycle and increases the duty cycle (Note 5) 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. 2006/12/20Rev. 1.6 Champion Microelectronic Corporation Page 5 CM3706 1.5MHz, 600mA Synchronous Step-Down Regulator Typical Performance Characteristics (Test Figure 1 above unless otherwise specified) 2006/12/20Rev. 1.6 Champion Microelectronic Corporation Page 6 CM3706 1.5MHz, 600mA Synchronous Step-Down Regulator Output Voltage vs Temperature OUTPUT VOLTAGE (V) 1.23 1.22 1.21 Vin=5V Vout=1.2V 1.2 ILoad=600mA 1.19 1.18 1.17 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 TEMPERATURE (℃) Pulse Skipping Mode Operation SW 1V/DIV ILoad 20mA/DIV Vin=3.6V Vout=1.8V Iload=10.29mA 1us Discontinuous Operation SW 1V/DIV Vo ut 0.5V/DIV ILoa d 20mA/DIV ILoa d 20 0mA/DIV Vin=3.6V Vout=1.8V Iloa d=22.24mA 0.2 u s Vout 20mV/DIV 200us Vin=5V Vout=2.5V ILOAD=0mA TO 600mA 2006/12/20Rev. 1.6 0.5ms Load step Vout 20mV/DIV ILoad 0.2A/DIV ILoad 0.2A/DIV Vin=3.6 V Vou t=1 .2 V Iloa d =6 00 mA Load step Load step Vout 20mV/DIV Start-Up from shutdown ILoad 0.2A/DIV 200us Vin=5V Vout=2.5V ILOAD=50mA TO 600mA Champion Microelectronic Corporation 500us Vin=5V Vout=2.5V ILOAD=100mA TO 600mA Page 7 CM3706 1.5MHz, 600mA Synchronous Step-Down Regulator APPLICATIONS INFORMATION L1 Setting the Output Voltage Figure 2 above shows the basic application circuit with CM3706 adjustable output version. The external resistor sets the output voltage according to the following equation: 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. A low ESR input capacitor sized for maximum RMS current must be used Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. A 4.7µF ceramic capacitor for most applications is sufficient. Inductor Selection For most designs, the CM3706 operates with inductors of 1µH to 4.7µH. Low inductance values are physically smaller but require faster switching, which results in some efficiency loss. The inductor value can be derived from the following equation: L= VOUT × (VIN − VOUT ) VIN × ∆I L × f OSC Where ∆I L is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in high ripple currents. Choose inductor ripple current approximately 35% of the maximum load current 600mA, or ∆I L =210mA. 2006/12/20Rev. 1.6 3 VIN 2.5V TO 5.5V Cin 4.7uF C1 ⎛ R2 ⎞ VOUT = 0.6V ⎜1 + ⎟ R1 ⎠ ⎝ R1=316KΩ ; R2= 316KΩ ; VOUT =1.2V R1=316KΩ ; R2= 470KΩ ; VOUT =1.5V R1=316KΩ ; R2= 630KΩ ; VOUT =1.8V R1=316KΩ ; R2= 1MΩ ; VOUT =2.5V R1=316KΩ ; R2= 1.42MΩ ; VOUT =3.3V. 4 IN 1 SW CM3706 RUN GND V FB 2 2.2uH OUT R2 1% 634k 5 Cout 10uF R1 316K 1% 22PF C3 C2 Figure2 Application Circuit with adjustable output versions For output voltages above 2.0V, when light-load efficiency is important, the minimum recommended inductor is 2.2µH. For optimum voltage-positioning load transients, choose an inductor with DC series resistance in the 50mΩ to 150mΩ range. For higher efficiency at heavy loads, or minimal load regulation (but some transient overshoot), the resistance should be kept below 100mΩ. The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation (600mA+105mA). Output Capacitor Selection The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current.The output ripple VOUT is determined by: ∆VOUT ≤ ⎞ VOUT × (VIN − VOUT ) ⎛ 1 ⎟⎟ × ⎜⎜ ESR + 8 3 VIN × f OSC × L × f × C osc ⎠ ⎝ Input Zener Selection In USB device application, we will add zener. The zener can be reduced the surge voltage when device plug in and plug out. Application circuit is show in Figure3. Champion Microelectronic Corporation Page 8 CM3706 1.5MHz, 600mA Synchronous Step-Down Regulator APPLICATION CIRCUIT Application Circuit for USB device 3 2.2uH CM3706 RUN GND V FB 5 1 634k 4 IN VIN 2.5V TO 5.5V OUT SW Cout 10uF 2 Zener 5.6V Cin 4.7uF 316K 22PF Figure 3 Application Circuit for USB device 2006/12/20Rev. 1.6 Champion Microelectronic Corporation Page 9 CM3706 1.5MHz, 600mA Synchronous Step-Down Regulator PACKAGE DIMENSION Package Description Note5: Package outline exclusive of mold flash and metal burr. 2006/12/20Rev. 1.6 Champion Microelectronic Corporation Page 10 CM3706 1.5MHz, 600mA Synchronous Step-Down Regulator IMPORTNT NOTICE Champion Microelectronic Corporation (CMC) reserves the right to make changes to its products or to discontinue any integrated circuit product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current. A few applications using integrated circuit products may involve potential risks of death, personal injury, or severe property or environmental damage. CMC integrated circuit products are not designed, intended, authorized, or warranted to be suitable for use in life-support applications, devices or systems or other critical applications. Use of CMC products in such applications is understood to be fully at the risk of the customer. In order to minimize risks associated with the customer’s applications, the customer should provide adequate design and operating safeguards. HsinChu Headquarter Sales & Marketing 5F, No. 11, Park Avenue II, Science-Based Industrial Park, HsinChu City, Taiwan 300 7F-6, No.32, Sec. 1, Chenggong Rd., Nangang District, Taipei City 115, Taiwan T E L : +886-3-567 9979 F A X : +886-3-567 9909 http://www.champion-micro.com T E L : +886-2-2788 0558 F A X : +886-2-2788 2985 2006/12/20Rev. 1.6 Champion Microelectronic Corporation Page 11