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CM3718
1.5A LOW-NOISE PWM STEP-DOWN REGULATOR
GENERAL DESCRIPTION
The CM3718 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 CM3718 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 0.1A. The CM3718 can deliver over 1.5A. The output voltage can be adjusted from VREF to VIN. The input range is from 2.0V to 5.0V. Other features of the CM3718 include high efficiency, low dropout voltage. It is available in a space-saving 8-pin SOP package.
FEATURES
Patent Number #6,452,366 1.2MHz switching and synchronization Dynamic output-voltage adjustment from VREF to VIN 1.5A Guaranteed Output Current 95% Efficiency No Schottky Diode Required External Soft Start 8-pin PSOP power packages
APPLICATIONS
Cellular Phone Cordless Phone PDAs and Handy-Terminals CPU I/O Supplies Notebook Chipset Supplies Battery Operated Devices
PIN CONFIGURATION
PSOP-8 (PT-08) Top View
1 2 3 4
VIN GND SD VREF
PVIN LX PGND VFB
8 7 6 5
2005/02/02 Rev. 1.5
Champion Microelectronic Corporation
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CM3718
1.5A LOW-NOISE PWM STEP-DOWN REGULATOR
PIN DESCRIPTION
Pin No. CM3718 1 2 3 Symbol Description Min. VIN GND SD Voltage supply for internal circuits Ground for internal reference voltage divider CMOS input level VOUT Set Voltage Feedback node for the VOUT Ground for output power transistors Inductor connection to the Drains of the internal power MOSFETs Voltage supply for output power transistors 2 2.5 5.5 5.5 V V Shutdown level Enable level 0.75 x VIN 0 1.1 VREF VIN + 0.3 2.0 VIN V V V 2 Operating Rating Typ. Max. 2.5 5.5 Uni t V
4 5 6 7 8
VREF VFB PGND LX PVIN
ORDERING INFORMATION
Part Number CM3718IS CM3718GIS* Temperature Range -40 to 85 -40 to 85 Package 8-Pin PSOP (PS08) 8-Pin PSOP (PS08)
*Note: G : Suffix for Pb Free Product
BLOCK DIAGRAM
VIN1 1 SD 3 PVIN 8
GND
2 Oscillator Ramp Generator
PW M Controller Thermal Protection
MOS
7
LX
VREF
4
Error Amp
5 VFB
6 PG ND
2005/02/02 Rev. 1.5
Champion Microelectronic Corporation
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CM3718
1.5A LOW-NOISE PWM STEP-DOWN REGULATOR
ABSOLUTE MAXIMUM RATINGS
Absolute maximum ratings are those values beyond which the device could be permanently damaged. PVIN/VIN ...........................................................-0.3V to 6.0V Voltage on Any Other Pin ............ GND - 0.3V to VIN + 0.3V Output Current, Source or Sink ......................................1.5A Junction Temperature ........................... ............150C Storage Temperature ............................. -65C to 125C Lead Temperature (Soldering, 5 sec).................... 260C Thermal Dissipation(JC )..... ....................... .50C/W
OPERATING CONDITIONS
Temperature Range ............................. -40C to 85C PVIN Operating Range .........................2.0V to 4.0V
(Unless otherwise stated, these specifications apply TA=25C; VIN=+3.3V and PVIN=+3.3V) maximum ratings are stress ratings only and functional device operation is not implied. (Note 1) Symbol SWITCHING REGULATOR VREF fsw IOUT(RMS) IOUT(PEAK) MOSFETs RDS(ON) SUPPLY IVIN IPVIN Quiescent Current VFB = 1.4V LC unconnected VFB = 1.4V LC unconnected 220 500 A A Drain to Source on-State Resistance PVIN=5V 250 m Adjustable Output Voltage Switching Frequency Maximum Output RMS Current Maximum Output Peak Current CM3718 CM3718 CM3718 VREF 1.2 1.5 3 VIN V MHz A A Parameter Test Conditions CM3718 Min. Typ. Max. Unit
ELECTRICAL CHARACTERISTICS
2005/02/02 Rev. 1.5
Champion Microelectronic Corporation
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CM3718
1.5A LOW-NOISE PWM STEP-DOWN REGULATOR
FUNCTIONAL DESCRIPTION
The CM3718 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 Fixed-frequency operation enables easy post-filtering, thereby providing excellent noise characteristics. As a result, the CM3718 is an ideal choice for many small wireless systems.
INPUTS
The input voltage reference pin, VREF determine the output voltages (LX). If a specific voltage is forced at the VREF pin, the
improves efficiency and eliminates an external Schottky diode. 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.
VREF The reference voltage could be ranged from 1.1V to VIN.
OUPUTS
The output voltage pins (LX) are tied to the RF power amp, via an external inductor. Output voltage is determined by the VREF inputs.
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
NOTE: JP3---->USEING EXTERNAL VOLTAGE SETING BOARD (PIN 1,2 SHORT)
1 D1 SK12 JP1 JUMPER C2 105 1 L1 3.3uH/2A 2 D2 SK12 2 1 J2 VTT 1 2 J3 VREF-OUT R5 0 C7 104 C6 47uf/6.3V VREF GND VIN SD 2 R1 100k 2 C3 470 2 1 8 7 6 5 U3 CM3718-8PIN 2 U2 CM-431 1 VCC 3 R7 0 R2 1k 1 R4 470 VCC
VDD 2 1 J1 PWR/IN
C1 100uf/6.3V
5 4 3
TP1 BNC 1
LX
PGND
PVIN
VFB
1
2
3
1 R8 5.1 JUMPER VDD JP2 2
105 C4
4
JP3 1 2 3 CON3
C5 104P
2 R3 100k
1
JP4
on/off sw
2005/02/02 Rev. 1.5
Champion Microelectronic Corporation
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CM3718
1.5A LOW-NOISE PWM STEP-DOWN REGULATOR
LOAD REGULATION
Vin=5V, VREF input=1.09V CM3718
CM3718
Vin=5V, VREF input=4.04V
5
2
Vout(V)
Vout(V)
4
1
3
0.05 0.2 0.4 0.6
0
2 4 6 05 0. 0. 0. 0.
Iout(A)
LOAD TRANSIENT RESPONSE
CM3718 Transient Response VREF=1V, (IOUT from 1.5A- 0A) CM3718 Transient Response VREF=1V, (IOUT from 0A- 1.5A)
CM3718 Transient Response VREF=4V(IOUT from 1.5A- 0A) CM3718 Transient Response VREF=4V(IOUT from 0A- 1.5A)
2005/02/02 Rev. 1.5
0.
Iout(A)
8
Champion Microelectronic Corporation
1
0.8
1
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CM3718
1.5A LOW-NOISE PWM STEP-DOWN REGULATOR
VOUT OUTOUT RIPPLE AND NOISE
CM3718 VREF=1V, Load=0.5A CM3718 VREF=1V, Load=1.0A CM3718 VREF=1V, Load=1.5A
CM3718 VREF=4V, Load=0.5A
CM3718 VREF=4V, Load=1.0A
CM3718 VREF=4V, Load=1.5A
VOLTAGE SETTING STEP RESPONSE
CM3718 (VREF from 1V- 4V), Load=0.5A CM3718 VREF=1V-4V, Load=1.0A CM3718 VREF=1V-4V, Load=1.5A
CM3718 VREF=4V-1V, Load=0.5A
CM3718 VREF=4V-1V, Load=1.0A
CM3718 VREF=4V-1V, Load=1.5A
2005/02/02 Rev. 1.5
Champion Microelectronic Corporation
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CM3718
1.5A LOW-NOISE PWM STEP-DOWN REGULATOR
IN-RUSH CURRENT
CM3718 Vin=5V, VREF=1V, Load=1.5A, Ip-p=1.81A CM3718 Vin=5V, VREF=4V, Load=1.5A, Ip-p=1.81A
EFFICIENCY
CM3718 efficiency (VOUT=1V, load from 0.05A~1.5A)
CM3718
CM3718 efficiency (VOUT =4V, load from 0.05A~1.5A)
CM3718
100.0% 95.0% 90.0% Efficiency Efficiency 85.0% 80.0% 75.0% 70.0% 65.0% 60.0% 0.05 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.5
100.0% 98.0% 96.0% 94.0% 92.0% 90.0% 88.0% 86.0% 84.0% 82.0% 80.0% 0.05 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.5
Iout(A)
Iout(A)
2005/02/02 Rev. 1.5
Champion Microelectronic Corporation
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CM3718
1.5A LOW-NOISE PWM STEP-DOWN REGULATOR
PCB LAYOUT
Top layer Bottom Layer
Silkscreen Top
Sold-mask
Top
Sold-mask Bottom
2005/02/02 Rev. 1.5
Champion Microelectronic Corporation
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CM3718
1.5A LOW-NOISE PWM STEP-DOWN REGULATOR
PACKAGE DIMENSION
8-PIN PSOP (PS08)
2005/02/02 Rev. 1.5
Champion Microelectronic Corporation
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CM3718
1.5A 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
5F, No. 11, Park Avenue II, Science-Based Industrial Park, HsinChu City, Taiwan 300 T E L : +886-3-567 9979 F A X : +886-3-567 9909 http://www.champion-micro.com
Sales & Marketing
11F, No. 306-3, Sec. 1, Ta Tung Rd., Hsichih, Taipei Hsien, Taiwan 221 T E L : +886-2-8692 1591 F A X : +886-2-8692 1596
2005/02/02 Rev. 1.5
Champion Microelectronic Corporation
Page 10

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