View CM3706IM25_1226925.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

CM3706
1.5MHz, 600mA Synchronous Step-Down Regulator
GENERAL DESCRIPTION
The CM3706 is a 1.5MHz constant frequency, slope compensated current mode PWM step-down converter. The device integrates a main switch and a synchronous rectifier for high efficiency without an external Schottky diode. It is ideal for powering portable equipment that runs from a single cell lithium-Ion (Li+) battery. The CM3706 can supply 600mA of load current from a 2.5V to 5.5V input voltage. The output voltage can be regulated as low as 0.6V. The CM3706 can also run at 100% duty cycle for low dropout operation, extending battery life in portable system. Idle mode operation at light loads provides very low output ripple voltage for noise sensitive applications. The CM3706 is offered in a low profile (1mm) 5-pin, thin TSOT package, and is available in an adjustable version.
FEATURES
High Efficiency: Up to 96% 1.5Mhz Constant Switching Frequency 600mA Output Current at VIN=3V Integrated Main switch and synchronous rectifier. No Schottky Diode Required 2.5V to 5.5V Input Voltage Range Output Voltage as Low as 0.6V 100% Duty Cycle in Dropout Low Quiescent Current: 300A Slope Compensated Current Mode Control for Excellent Line and Load Transient Response Short Circuit Protection Thermal Fault Protection <1uA Shutdown Current Space Saving 5-Pin Thin TSOT23 package
APPLICATIONS
Cellular and Smart Phones MP3 Players Portable Instruments Digital Still and Video Cameras
Microprocessors and DSP Core Supplies Wireless and DSL Modems PDAs
TYPICAL APPLICATIONS
IN 2.5V TO 5.5V
Cin 4.7uF
4
3
2.2uH
VIN
1
SW
634k
OUT
CM3706 RUN GND V FB
2
316K
5
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
5 4
FB
GND
2
RUN
1
BLOCK DIAGRAM
2006/12/20Rev. 1.6
Champion Microelectronic Corporation
SW
3
VIN
Page 2
CM3706
1.5MHz, 600mA Synchronous Step-Down Regulator
PIN DESCRIPTION
Pin No. 1 RUN Symbol Description Regulator Enable control input. Drive RUN above 1.5V to turn on the part. Drive RUN below 0.3V to turn it off. 2 3 4 5 GND SW VIN FB Ground Pin. 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. Supply Input Pin. Must be closely decoupled to GND, Pin 2, with a 2.2F or greater ceramic capacitor. VFB (CM3706): Feedback Input Pin. Connect FB to the center point of the external resistor divider. The feedback threshold voltage is 0.6V. In shutdown, all functions are disabled drawing <1A supply current. Do not leave RUN floating.
ORDERING INFORMATION
Part Number CM3706IM25 CM3706GIM25 Voltage Adj Adj Temperature Range -40 to +85 -40 to +85 Package TSOT23-5 TSOT23-5
CM3706
XXX
Lead Free
Suffix for Temperature I : -40 to +85
Package
Blank : Normal G: Lead Free 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) ........... ........................ 125C SW Voltage.............................................. - 0.3V to (VIN + 0.3V) Storage Temperature Range ....................... - 65C to 150C
Operating Temperature Range.....................-40C to +85C Lead Temperature (Soldering, 10 sec)......................... 300C
OPERATING CONDITIONS
Temperature Range ............................. -40C to 85C 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 JA 250C/W JC 110C/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)(JA) Note 3: Thermal Resistance is specified with approximately 1 square of 1 oz copper.
ELECTRICAL CHARACTERISTICS
Parameter Input Voltage Range Input DC Supply Current Active Mode Shutdown Mode
(Unless otherwise stated, these specifications apply TA=25C; VIN=+3.6V) maximum ratings are stress ratings only and functional device operation is not implied.
Conditions
MIN 2.5
TYP
MAX 5.5
unit V A A V V V nA %/V V V V %/V %/mA A
VFB=0.5V VFB=0V, VIN=4.2V 0.5880 0.5865 0.5850
270 0.08 0.6000 0.6000 0.6000
400 1.0 0.6120 0.6135 0.6150 30
TA = +25C Regulated Feedback Voltage TA= 0C TA 85C TA= -40C TA 85C VFB Input Bias Current Reference Voltage Line Regulation Regulated Output Voltage Output Voltage Line Regulation Output Voltage Load Regulation Peak Inductor Current Oscillator Frequency RDS(ON) of P-CH MOSFET RDS(ON) of N-CH MOSFET SW Leakage RUN Threshold RUN Leakage Current Thermal Shutdown Trip Threshold Output over voltage lockout VFB = 0.65V VIN = 2.5V to 5.5V,
CM3706-1.2, -40C TA 85C CM3706-1.5, -40C TA 85C CM3706-1.8, -40C TA 85C
0.11 1.164 1.455 1.746 1.200 1.500 1.800 0.11 0.0015 1.2 1.2 1.5 0.3 0.2 0.01 0.3 0.45 0.1 150
0.4 1.236 1.545 1.854 0.40
VIN = 2.5V to 5.5V,IOUT=10mA IOUT from 10 to 600mA VIN=3V, VFB=0.5V or VOUT=90% Duty Cycle <35% VFB=0.6V or VOUT=100% ISW = 300mA ISW = -300mA VRUN = 0V, VSW= 0V or 5V, VIN = 5V -40C TA 85C
1.8 0.50 0.45 1 1.5 1
MHz A V A mV
VOVL = VOVL - VFB
60
Note 4: 100% production test at +25C. 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
CM3706 is a monolithic switching mode Step-Down DC-DC converter. It utilizes internal MOSFETs to achieve high efficiency and can generate very low output voltage by using internal reference at 0.6V. It operates at a fixed switching frequency, and uses the slope compensated current mode architecture. This Step-Down DC-DC Converter supplies 600mA output current at VIN = 3V with input voltage range from 2.5V to 5.5V.
Idle Mode Operation
At very light loads, the CM3706 automatically enters Idle Mode. In the Idle Mode, the inductor current may reach zero or reverse on each pulse. automatically skip pulses to maintain output regulation. The bottom MOSFET is turned off by the current reversal comparator, IZERO, and the switch voltage will ring. This is discontinuous mode operation, and is normal behavior for the switching regulator. The PWM control loop will
Current Mode PWM Control
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. limits the peak inductor current. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current starts to reverse, as 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. The current comparator, ICOMP,
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.
Note 5: The duty cycle D of a step-down converter is defined as:
D = TON x f OSC x 100%
frequency (1.5Mhz).
V OUT x100% VIN
where TON is the main switch on time, and fOSC is the oscillator
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
1.23
VOLTAGE (V) OUTPUT
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
Discontinuous Operation
Start-Up from shutdown
SW 1V/DIV ILoad 20mA/DIV Vin=3.6V Vout=1.8V Iload=10.29mA 1us
SW 1V/DIV ILoad 20mA/DIV Vin=3.6V Vout=1.8V Iloa d=22.24mA 0.2 u s
Vo ut 0.5V/DIV ILoa d 20 0mA/DIV
Vin=3.6 V Vou t=1 .2 V Iloa d =6 00 mA
0.5ms
Load step
Load step
Load step
Vout 20mV/DIV
Vout 20mV/DIV
Vout 20mV/DIV
ILoad 0.2A/DIV 200us Vin=5V Vout=2.5V ILOAD=0mA TO 600mA
ILoad 0.2A/DIV 200us Vin=5V Vout=2.5V ILOAD=50mA TO 600mA
ILoad 0.2A/DIV 500us Vin=5V Vout=2.5V ILOAD=100mA TO 600mA
2006/12/20Rev. 1.6
Champion Microelectronic Corporation
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:
IN 2.5V TO 5.5V
Cin 4.7uF
4
3
2.2uH
VIN
1
SW CM3706 RUN GND V FB
2
OUT
1% 634k
5
Cout 10uF 22PF
R2
R1
316K
C1
1%
C3
C2
R2 VOUT = 0.6V 1 + R1
R1=316K ; R2= 316K ; VOUT =1.2V R1=316K ; R2= 470K ; VOUT =1.5V R1=316K ; R2= 630K ; VOUT =1.8V R1=316K ; R2= 1M ; VOUT =2.5V R1=316K ; R2= 1.42M ; VOUT =3.3V. 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 4.7F ceramic capacitor for most applications is sufficient. Inductor Selection For most designs, the CM3706 operates with inductors of 1H to 4.7H. 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:
Figure2 Application Circuit with adjustable output versions For output voltages above 2.0V, when light-load efficiency is important, the minimum recommended inductor is 2.2H. For optimum voltage-positioning load transients, choose an inductor with DC series resistance in the 50m to 150m range. For higher efficiency at heavy loads, or minimal load regulation (but some transient overshoot), the resistance should be kept below 100m. 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:
L=
VOUT x (VIN - VOUT ) VIN x I L x f OSC
VOUT
VOUT x (VIN - VOUT ) 1 x ESR + 8 x f osc x C 3 VIN x f OSC x L
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.
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.
2006/12/20Rev. 1.6
Champion Microelectronic Corporation
Page 8
CM3706
1.5MHz, 600mA Synchronous Step-Down Regulator
APPLICATION CIRCUIT
Application Circuit for USB device
IN 2.5V TO 5.5V
Cin 4.7uF
4
3
2.2uH
VIN
SW
634k
OUT
CM3706 RUN GND VFB 5 1
2
Zener 5.6V 316K
Cout 10uF 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
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
7F-6, No.32, Sec. 1, Chenggong Rd., Nangang District, Taipei City 115, Taiwan T E L : +886-2-2788 0558 F A X : +886-2-2788 2985
2006/12/20Rev. 1.6
Champion Microelectronic Corporation
Page 11

▲Up To Search▲

Price & Availability of CM3706IM25

	To Download CM3706IM25 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .