CM3708 ETC | Alldatasheet
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3A L OW-NOISE PWM S TEP-DOWN R EGULATOR 2004/09/15 Rev. 1.2 Champion Microelectronic Corporation Page 1 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. 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. 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
APPLICATIONS
Cellular Phone Cordless Phone PDAs and Handy-Terminals AGP Chipset Supplies CPU I/O Supplies Notebook Chipset Supplies Battery Operated Devices PIN CONFIGURATION PSOP-16 (PS16) / PTSSOP-16 (PT16) Top View VIN1 PVIN1 LX1 PGND1 AGND SD VREF AGSEN VIN2 PVIN2 LX2 PGND2 AGND VFB NC AGND
3A L OW-NOISE PWM S TEP-DOWN R EGULATOR 2004/09/15 Rev. 1.2 Champion Microelectronic Corporation Page 2 PIN DESCRIPTION Operating Rating Pin No. Symbol Description Min. Typ. Max. Unit 1,16 VIN1, VIN2 Voltage supply for internal circuits 2 2.5 5 V 2,15 PVIN1, PVIN2 Voltage supply for out put power transistors 2 2.5 5 V 3,14 LX1, LX2 Inductor connection to the Drains of the internal power MOSFETs 5 V 4,13 PGND1, PGND2 Ground for output power transistors 5,9,12 AGND Ground for internal re ference voltage divider
8 AGSEN Ground for remote sensing
6 SD Shutdown active high. CMOS input level 0.75 x VIN VIN + 0.3V V 7 VREF V OUT Set Voltage 1.1 VIN V
10 NC No Connection
11 VFB Feedback node for the V OUT 5 V
3A L OW-NOISE PWM S TEP-DOWN R EGULATOR 2004/09/15 Rev. 1.2 Champion Microelectronic Corporation Page 3
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 Junction Temperature ...…………………… …………150°C Absolute maximum ratings are those values beyond which the OPERATING CONDITIONS ELECTRICAL CHARACTERISTICS (Unless otherwise stated, these specifications apply T A=25°C; VIN=+3.3V and PVIN=+3.3V) maximum ratings are stress ratings only and functional device operation is not implied. (Note 1) CM3708 Symbol Parameter Test Conditions Min. Typ. Max. Unit SWITCHING REGULATOR VREF Adjustable Output Voltage VREF VIN V fsw Switching Frequency CM3708 480 660 KHz IOUT(RMS) Maximum Output RMS Current CM3708 3.0 A IOUT(PEAK) Maximum Output Peak Current CM3708 6.0 A MOSFETs RDS(ON) Drain to Source on-Stat e Resistance PVIN=5V 150 180 mΩ SUPPLY IVIN Quiescent Current VFB = 1.4V LC unconnected 200 µA IPVIN VFB = 1.4V LC unconnected 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
3A L OW-NOISE PWM S TEP-DOWN R EGULATOR 2004/09/15 Rev. 1.2 Champion Microelectronic Corporation Page 4 FUNCTIONAL DESCRIPTION The CM3708 step-down, pulse-width-modulated (PWM), DC-DC converter has an adjustable output range from VREF to the input voltage (VIN). An internal synchronous rectifier improves efficiency and eliminates an external Schottky diode. Fixed-frequency operation enables easy post-filtering, thereby providing excellent noise characteristics. As a result, the CM3708 is an ideal choice for many small wireless systems. VREF The reference voltage could be ranged from 1.1V to VIN. OUPUTS The output voltage pins (LX1, LX2) are tied to the RF power amp, via an external inductor. Output voltage is determined by the VREF inputs. INPUTS The input voltage reference pin, VREF determine the output voltages (LX1, LX2). If a specific voltage is forced at the VREF pin, the output voltage follows the voltage at the VREF pin. OTHER SUPPLY VOLTAGES Several inputs are provided for the supply voltages: PVIN and VIN. The PVIN provide the power supply to the power MOSFETs. VIN provides the voltage supply to the logic section and internal error amplifiers. FEEDBACK The VFB pin is an input that can be used for closed loop compensation. This input is derived from the voltage output. AGND pin is a contact node of internal resistor divider for remote sense. APPLICATION CIRCUIT R2 200k 470uf/6.3V 10uf/6.3V DC-INPUT Vout 1 U1 CM3708 8 9 PVIN1 VIN1 LX1 PGND2 LX2 PVIN2 VIN2 PGND1 AGND SD VREF AGSEN AGND NC VFB AGND C12 102 PVIN PVINVIN 3.3uH 104 C10 100uf/6.3V 104 C11 104 PVIN VREF 100uf/6.3V 220uf/6.3V R1 5R1 104 VIN 104 104
3A L OW-NOISE PWM S TEP-DOWN R EGULATOR 2004/09/15 Rev. 1.2 Champion Microelectronic Corporation Page 5 PACKAGE DIMENSION 16-PIN PTSSOP (PT16) θ θ 16-PIN PSOP (PS16) θ θ
3A L OW-NOISE PWM S TEP-DOWN R EGULATOR 2004/09/15 Rev. 1.2 Champion Microelectronic Corporation Page 6 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 in volve potential risks of death, personal injury, or severe property or environmental damage. CMC integrated circui t 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 un derstood to be fully at the risk of the customer. In order to minimize risks associated with the customer’s applications, the cu stomer 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 T E L : +886-2-8692 1591 FAX: +886-3-567 9909 F A X : +886-2-8692 1596 http://www.champion-micro.com