CM3708 3A LOW-NOISE PWM STEP-DOWN REGULATOR GENERAL DESCRIPTION FEATURES The CM3708 is a low-noise, pulse-width-modulated (PWM), DC-DC step-down converter. It powers logic and transmitters in small wireless systems such as cellular phones, communicating PDAs, and handy-terminals. The device features an internal synchronous rectifier for high efficiency; it requires no external Schottky diode. Excellent noise characteristics and fixed-frequency operation provide easy post-filtering. The CM3708 is ideally suited for Li-lon battery applications. It is also useful for +3V or +5V fixed input applications. Patent Filed #6,452,366 600KHz switching and synchronization Dynamic output-voltage adjustment from VREF to VIN 3A Guaranteed Output Current 95% Efficiency No Schottky Diode Required External Soft start 16-pin PSOP/PTSSOP power packages The device operates in one of four modes. Forced PWM mode operates at a fixed frequency regardless of the load. Shutdown mode places the device in standby, reducing quiescent supply current to under 0.1µA. The CM3708 can deliver over 3.0A. The output voltage can be adjusted from VREF to VIN. The input range is from 2.0V to 5.0V. Other features of the CM3708 include high efficiency, low dropout voltage. It is available in a space-saving 16-pin SOP & TSSOP package. APPLICATIONS Cellular Phone CPU I/O Supplies Cordless Phone Notebook Chipset Supplies PDAs and Handy-Terminals Battery Operated Devices AGP Chipset Supplies PIN CONFIGURATION PSOP-16 (PS16) / PTSSOP-16 (PT16) Top View 2004/09/15 Rev. 1.2 1 VIN1 VIN2 16 2 PVIN1 PVIN2 15 3 LX1 LX2 14 4 PGND1 PGND2 13 5 AGND AGND 12 6 SD VFB 11 7 VREF NC 10 8 AGSEN AGND Champion Microelectronic Corporation 9 Page 1 CM3708 3A LOW-NOISE PWM STEP-DOWN REGULATOR PIN DESCRIPTION Pin No. Symbol Description Min. Operating Rating Typ. Max. Unit 1,16 VIN1, VIN2 Voltage supply for internal circuits 2 2.5 5 V 2,15 PVIN1, PVIN2 Voltage supply for output power transistors 2 2.5 5 V 3,14 LX1, LX2 Inductor connection to the Drains of the internal 5 V 0.75 x VIN + V VIN 0.3V 1.1 VIN V 5 V power MOSFETs 4,13 PGND1, PGND2 Ground for output power transistors AGND Ground for internal reference voltage divider 8 AGSEN Ground for remote sensing 6 SD Shutdown active high. CMOS input level 5,9,12 7 VREF VOUT Set Voltage 10 NC No Connection 11 VFB Feedback node for the VOUT BLOCK DIAGRAM AGND 5 AGND 9 NC VIN1 VIN2 SD PVIN1 PVIN2 10 1 16 6 2 15 Oscillator Ramp Generator AGND 12 PW M Controller VREF 2004/09/15 Rev. 1.2 Error Amp 7 8 11 AGSEN VFB MOS 3 LX1 14 LX2 Therm al Protection 4 PGND1 Champion Microelectronic Corporation 13 PGND2 Page 2 CM3708 3A LOW-NOISE PWM STEP-DOWN REGULATOR ORDERING INFORMATION Part Number Temperature Range Package CM3708IT -40℃ to 85℃ 16-Pin PTSSOP (PT16) CM3708GIT* -40℃ to 85℃ 16-Pin PTSSOP (PT16) CM3708IS -40℃ to 85℃ 16-Pin PSOP (PS16) CM3708GIS* -40℃ to 85℃ 16-Pin PSOP (PS16) *Note: G : Suffix for Pb Free Product ABSOLUTE MAXIMUM RATINGS Absolute maximum ratings are those values beyond which the Junction Temperature ...…………………… …………150°C device could be permanently damaged. Storage Temperature ……................……. -65°C to 125°C PVIN/VIN …………......................................….......-0.3V to 5.0V Lead Temperature (Soldering, 5 sec)……………….. 260°C Thermal Dissipation(θJC )….. ………………….. .50°C/W Voltage on Any Other Pin ………... GND – 0.3V to VIN + 0.3V Output Current, Source or Sink ……......…………........…...3.0A OPERATING CONDITIONS Temperature Range ............................. -40°C to 85°C PVIN Operating Range .........................2.0V to 5.0V ELECTRICAL CHARACTERISTICS (Unless otherwise stated, these specifications apply TA=25°C; VIN=+3.3V and PVIN=+3.3V) maximum ratings are stress ratings only and functional device operation is not implied. (Note 1) Symbol Parameter Test Conditions CM3708 Min. Typ. Max. Unit SWITCHING REGULATOR VREF Adjustable Output Voltage VREF VIN V 480 fsw Switching Frequency CM3708 660 KHz IOUT(RMS) Maximum Output RMS Current CM3708 3.0 A IOUT(PEAK) Maximum Output Peak Current CM3708 6.0 A Drain to Source on-State Resistance PVIN=5V 180 mΩ MOSFETs RDS(ON) 150 SUPPLY IVIN Quiescent Current IPVIN VFB = 1.4V LC unconnected VFB = 1.4V LC unconnected 200 µA 500 µA Note 1: Limits are guaranteed by 100% testing, sampling, or correlation with worst case test conditions Note 2: VIN, PVIN = 3.3V ±10% Note 3: It’s not 100% test 2004/09/15 Rev. 1.2 Champion Microelectronic Corporation Page 3 CM3708 3A LOW-NOISE PWM STEP-DOWN REGULATOR FUNCTIONAL DESCRIPTION The CM3708 step-down, pulse-width-modulated (PWM), INPUTS DC-DC converter has an adjustable output range from VREF The input voltage reference pin, VREF determine the output to the input voltage (VIN). An internal synchronous rectifier voltages (LX1, LX2). If a specific voltage is forced at the VREF improves efficiency and eliminates an external Schottky diode. pin, the output voltage follows the voltage at the VREF pin. Fixed-frequency operation enables easy post-filtering, thereby providing excellent noise characteristics. As a result, the OTHER SUPPLY VOLTAGES CM3708 is an ideal choice for many small wireless systems. Several inputs are provided for the supply voltages: PVIN and VIN. VREF The PVIN provide the power supply to the power MOSFETs. The reference voltage could be ranged from 1.1V to VIN. VIN provides the voltage supply to the logic section and internal error amplifiers. OUPUTS The output voltage pins (LX1, LX2) are tied to the RF power FEEDBACK amp, via an external inductor. Output voltage is determined by The VFB pin is an input that can be used for closed loop the VREF inputs. compensation. This input is derived from the voltage output. AGND pin is a contact node of internal resistor divider for remote sense. APPLICATION CIRCUIT L1 3.3uH Vout J1 1 2 C2 104 C1 220uf/6.3V VIN 10uf/6.3V C4 104 C3 1 PVIN 2 C6 100uf/6.3V C7 104 3 4 5 6 VREF 7 8 U1 CM3708 VIN1 PVIN1 LX1 VIN2 PVIN2 LX2 PGND1 PGND2 AGND SD VREF AGSEN AGND VFB NC AGND VIN 16 R1 5R1 J2 DC-INPUT PVIN 1 2 PVIN 15 14 C8 13 104 12 C9 104 C5 C10 100uf/6.3V 470uf/6.3V 11 10 9 C11 104 R2 200k 1 2 1 2 R3 1k 2004/09/15 Rev. 1.2 C12 102 Champion Microelectronic Corporation Page 4 CM3708 3A LOW-NOISE PWM STEP-DOWN REGULATOR PACKAGE DIMENSION 16-PIN PTSSOP (PT16) θ θ 16-PIN PSOP (PS16) θ θ 2004/09/15 Rev. 1.2 Champion Microelectronic Corporation Page 5 CM3708 3A LOW-NOISE PWM STEP-DOWN REGULATOR IMPORTANT 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 11F, No. 306-3, Sec. 1, Ta Tung Rd., Hsichih, Taipei Hsien Taiwan 221 T E L : +886-3-567 9979 F A X : +886-3-567 9909 http://www.champion-micro.com T E L : +886-2-8692 1591 F A X : +886-2-8692 1596 2004/09/15 Rev. 1.2 Champion Microelectronic Corporation Page 6