CHAMP CM3706IM25 1.5mhz, 600ma synchronous step-down regulator Datasheet

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