CM3708A ETC | Alldatasheet
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Technical content
3A L OW-NOISE PWM S TEP-DOWN R EGULATOR GENERAL DESCRIPTION
FEATURES
The CM3708A 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 CM3708A 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 CM3708A 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 CM3708A 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 16-pin PSOP/PTSSOP power packages 6A Low Noise Current Limit Protection External Soft Start Rail to Rail output Buck Converter
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 PVI N1 LX1 PG ND 1 AG ND SD VR EF AG SEN VIN2 PVI N2 LX2 PG ND2 AG ND VFB NC AG ND 2004/12/13 C hampion Microelectronic Corporation Page 1
3A L OW-NOISE PWM S TEP-DOWN R EGULATOR 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 output power transistors 2 2.5 5 V 3,14 LX1, LX2 Inductor co nnection to the Drains of the intern al power MOSFETs 5 V 4,13 PGND1, PGND2 Ground for output power transistors 5,9,12 AGND Ground for internal reference 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 VOUT Set Voltage 0 VIN V
10 NC No Connection
11 VFB Feedback node for the VOUT 5 V
2004/12/13 C hampion Microelectronic Corporation Page 2
3A L OW-NOISE PWM S TEP-DOWN R EGULATOR
ORDERING INFORMATION
Part Number Temperature Range Package CM3708AIT -40℃ to 85℃ 16-Pin PTSSOP (PT16) CM3708AGIT* -40℃ to 85℃ 16-Pin PTSSOP (PT16) CM3708AIS -40℃ to 85℃ 16-Pin PSOP (PS16) CM3708AGIS* -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 o therwise stated , these sp ecifications ap ply 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) CM3708A Symbol Parameter Test Conditions Min. Typ. Max. Unit SWITCHING REGULATOR VREF Adjustable Output Voltage 0 VIN V fsw Switching Frequency CM3708A 480 660 KHz IOUT(RMS) Maximum Output RMS Current CM3708A 3.0 A IOUT(PEAK) Maximum Output Peak Current CM3708A 6.0 A Ilimit Current limit CM3708A 6 A MOSFETs RDS(ON) Drain to Source on-State Resistance PVIN=5V 150 180 mΩ SUPPLY IVIN Quiescent Current VFB = 1.4V LC unconnected 200 µA IPVIN Quiescent Current 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 2004/12/13 C hampion Microelectronic Corporation Page 3
3A L OW-NOISE PWM S TEP-DOWN R EGULATOR FUNCTIONAL DESCRIPTION The CM3708A 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 CM3708A is an ideal choice for many small wireless systems. VREF The reference voltage could be ranged from 0V 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 so it can be from 0V to VIN. Internal Power Switches: CM3708A has been integrated 2 Power MOSFETs whose RDS(ON) is around 100m Ohm each. Low Noise Current Limit: CM3708A’s current limit is a low noise current limit. It increase the system loop noise immunity while it is doing the current limit protection for the system. The current limit is around 6A for the normal 3A operation. 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 PVIN VIN PVIN PVIN 5R1 VREF VIN R2 200k 100uf/6.3V 104 J2 DC-INPUT U1 CM3708A 8 9 PVIN1 VIN1 LX1 PGND2 LX2 PVIN2 VIN2 PGND1 AGND SD VREF AGSEN AGND NC VFB AGND 104 220uf/6.3V 104 C12 102 104 3.3uH C11 104 Vout 1 10uf/6.3V C10 100uf/6.3V 104 C5 470uf/6.3V 2004/12/13 C hampion Microelectronic Corporation Page 4
3A L OW-NOISE PWM S TEP-DOWN R EGULATOR PACKAGE DIMENSION 16-PIN PTSSOP (PT16) θ θ 16-PIN PSOP (PS16) θ θ 2004/12/13 C hampion Microelectronic Corporation Page 5
3A L OW-NOISE PWM S TEP-DOWN R EGULATOR 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 appli cations using integrated circuit products may involve potential ri sks of death, p ersonal injury, or seve re property or e nvironmental damage. CMC integ rated circui t prod ucts a re not designed, intende d, autho rized, 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 c ustomer. In order to minimize risks associated with the cu stomer’s applications, the customer should p rovide ad equate desi gn a nd 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 2004/12/13 C hampion Microelectronic Corporation Page 6