CHAMP CM3706A 1.5mhz, 600ma synchronous step-down regulator Datasheet

CM3706A
1.5MHz, 600mA Synchronous Step-Down Regulator
GENERAL DESCRIPTION
FEATURES
The CM3706A is a high efficiency monolithic synchronous
◆
High Efficiency: Up to 96%
buck regulator using a constant frequency, current mode
◆
1.5Mhz Constant Switching Frequency
architecture. The device is available in an adjustable
◆
600mA Output Current at VIN=3V
version. Supply current with no load is 300uA and drops to
◆
Integrated Main switch and synchronous rectifier. No
Schottky Diode Required
<1uA in shutdown. The 2.5V to 6.5V input voltage range
makes the CM3706A ideally suited for single Li-Ion, two to
◆
2.5V to 6.5V Input Voltage Range
four AA battery-powered applications. 100% duty cycle
◆
Output Voltage as Low as 0.6V
provides low dropout operation, extending battery life in
◆
100% Duty Cycle in Dropout
portable systems. PWM pulse skipping mode operation
◆
Low Quiescent Current: 300µA
provides very low output ripple voltage for noise sensitive
◆
Slope Compensated Current Mode Control for Excellent Line
and Load Transient Response
applications. Switching frequency is internally set at
1.5MHz, allowing the use of small surface mount inductors
◆
Short Circuit Protection
and capacitors. The internal synchronous switch increases
◆
Thermal Fault Protection
efficiency and eliminates the need for an external Schottky
◆
<1uA Shutdown Current
diode. Low output voltages are easily supported with the
◆
Space Saving 5-Pin Thin TSOT23 package
0.6V feedback reference voltage.
APPLICATIONS
‹
Cellular and Smart Phones
‹
MP3 / MP4 Player
‹
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
CM3706A
RUN GND VFB
2
634k
5
316K
Cout
10uF
22PF
Figure 1. Basic Application Circuit with CM3706A adjustable version
2008/03/07 Rev. 1.0
Champion Microelectronic Corporation
Page 1
CM3706A
1.5MHz, 600mA Synchronous Step-Down Regulator
PIN CONFIGURATION
TSOT23-5
Top View
BLOCK DIAGRAM
2008/03/07 Rev. 1.0
Champion Microelectronic Corporation
Page 2
CM3706A
1.5MHz, 600mA Synchronous Step-Down Regulator
PIN DESCRIPTION
Pin No.
Symbol
Description
1
RUN
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 (CM3706A): Feedback Input Pin. Connect FB to the center point of the external resistor
divider. The feedback threshold voltage is 0.6V.
ORDERING INFORMATION/ MARKING
Adjustable Output Version
Part Number
CM3706AGIM25
2008/03/07 Rev. 1.0
Output
Adj
Top Mark
A1XY
Champion Microelectronic Corporation
Temp Range
-40°C to +85°C
Page 3
CM3706A
1.5MHz, 600mA Synchronous Step-Down Regulator
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 7.0V 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
Thermal Resistance (Note 3):
Package
TSOT23-5
ӨJA
ӨJC
250°C/W
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:
CM3706A : TJ = TA + (PD)╳(ӨJA)
Note 3: Thermal Resistance is specified with approximately 1 square of 1 oz copper.
2008/03/07 Rev. 1.0
Champion Microelectronic Corporation
Page 4
CM3706A
1.5MHz, 600mA Synchronous Step-Down Regulator
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
Conditions
Input Voltage Range
Input DC Supply Current
Active Mode
Shutdown Mode
Regulated Feedback Voltage
MAX
unit
6.5
V
VFB=0.5V
300
400
VFB=0V, VIN=4.2V
0.1
1.0
µA
µA
TA = +25°C
0.5880
0.6000
0.6120
V
TA= 0°C ≤ TA ≤ 85°C
0.5865
0.6000
0.6135
V
TA= -40°C ≤ TA ≤ 85°C
0.5820
0.6000
0.6180
V
±30
nA
0.01
0.4
%/V
0.04
0.40
%/V
VFB = 0.65V
Reference Voltage Line
Regulation
VIN = 2.5V to 5.5V,
Output Voltage Line Regulation
VIN = 2.5V to 5.5V,IOUT=10mA
Peak Inductor Current
TYP
2.5
VFB Input Bias Current
Output Voltage Load Regulation
MIN
IOUT from 10 to 600mA
VIN=3V, VFB=0.5V or VOUT=90%
Duty Cycle <35%
0.0015
%/mA
0.75
1.00
1.25
A
1.2
1.5
1.8
MHz
Oscillator Frequency
VFB=0.6V or VOUT=100%
RDS(ON) of P-CH MOSFET
ISW = 300mA
0.4
0.50
Ω
RDS(ON) of N-CH MOSFET
ISW = -300mA
0.35
0.45
Ω
SW Leakage
VRUN = 0V, VSW= 0V or 5V, VIN = 5V
±0.01
±1
µA
RUN Threshold
-40°C ≤ TA ≤ 85°C
0.45
1.5
V
±0.1
±1
µA
0.3
RUN Leakage Current
Thermal Shutdown Trip
Threshold
Output over voltage lockout
ΔVOVL = VOVL – VFB
150
℃
60
mV
Note 4: 100% production test at +25°C. Specifications over the temperature range are guaranteed by design and
characterization.
2008/03/07 Rev. 1.0
Champion Microelectronic Corporation
Page 5
CM3706A
1.5MHz, 600mA Synchronous Step-Down Regulator
FUNCTIONAL DESCRIPTION
Operation
Idle Mode Operation
CM3706A is a monolithic switching mode Step-Down DC-DC
At very light loads, the CM3706A 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 6.5V.
is normal behavior for the switching regulator.
Current Mode PWM Control
Maximum Load Current
The CM3706A 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
error voltage.
is above the
The current comparator, ICOMP, limitsthe peak
The PWM control loop will
inductor current. When the main switch is off, the synchronous
rectifier will be turned on immediately and stay on until either
Note 5: The duty cycle D of a step-down converter is defined
the inductor current starts to reverse, as indicated by the
as:
current reversal comparator, IZERO, or the beginning of the
D = TON × f OSC × 100% ≈
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 CM3706A 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 voltageminus 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.
2008/03/07 Rev. 1.0
Champion Microelectronic Corporation
Page 6
CM3706A
1.5MHz, 600mA Synchronous Step-Down Regulator
Typical Performance Characteristics
(Test Figure 1 above unless otherwise specified)
2008/03/07 Rev. 1.0
Champion Microelectronic Corporation
Page 7
CM3706A
1.5MHz, 600mA Synchronous Step-Down Regulator
Output Voltage vs Temperature
Pulse Skipping Mode Operation
Load step
2008/03/07 Rev. 1.0
Discontinuous Operation
Load step
Champion Microelectronic Corporation
Start-Up from shutdown
Load step
Page 8
CM3706A
1.5MHz, 600mA Synchronous Step-Down Regulator
APPLICATIONS INFORMATION
L1
Setting the Output Voltage
Figure 2 above shows the basic application circuit with
CM3706A adjustable output version. The external resistor
4
IN
Cin
4.7uF
⎛ R2 ⎞
VOUT = 0.6V ⎜1 +
⎟
R1 ⎠
⎝
1
SW
CM3706A
RUN GND VFB
OUT
VIN
2.5VTO
5.5V
sets the output voltage according to the following equation:
2.2uH
3
2
R2
1%634k
5
Cout
10uF
R1
316K
C1
22PF
1%
C3
C2
R1=316KΩ ; R2= 316KΩ ; VOUT =1.2V
R1=316KΩ ; R2= 470KΩ ; VOUT =1.5V
Figure2 Application Circuit with
R1=316KΩ ; R2= 630KΩ ; VOUT =1.8V
adjustable output versions
R1=316KΩ ; R2= 1MΩ ; VOUT =2.5V
R1=316KΩ ; R2= 1.42MΩ ; VOUT =3.3V.
For output voltages above 2.0V, when light-load efficiency is
Input Capacitor Selection
important, the minimum recommended inductor is 2.2µH.
The input capacitor reduces the surge current drawn from the
For optimum voltage-positioning load transients, choose an
input and switching noise from the device. The input capacitor
inductor with DC series resistance in the 50mΩ to 150mΩ
impedance at the switching frequency shall be less than input
range. For higher efficiency at heavy loads, or minimal load
source impedance to prevent high frequency switching current
regulation (but some transient overshoot), the resistance
passing to the input. A low ESR input capacitor sized for
should be kept below 100mΩ. The DC current rating of the
maximum RMS current must be used Ceramic capacitors with
inductor should be at least equal to the maximum load current
X5R or X7R dielectrics are highly recommended because of
plus half the ripple current to prevent core saturation
their low ESR and small temperature coefficients. A 4.7µF
(600mA+105mA).
ceramic capacitor for most applications is sufficient.
Output Capacitor Selection
Inductor Selection
The output capacitor is required to keep the output voltage
For most designs, the CM3706A operates with inductors of
ripple small and to ensure regulation loop stability. The output
1µH to 4.7µH. Low inductance values are physically smaller
capacitor must have low impedance at the switching frequency.
but require faster switching, which results in some efficiency
Ceramic
loss. The inductor value can be derived from the following
recommended due to their low ESR and high ripple current.The
equation:
output ripple VOUT is determined by:
L=
Where
ΔI L
VOUT × (V IN − VOUT )
V IN × ΔI L × f OSC
ΔVOUT ≤
is inductor Ripple Current. Large value
capacitors
with
X5R
or
X7R
dielectrics
are
⎞
VOUT × (V IN − VOUT ) ⎛
1
⎟⎟
× ⎜⎜ ESR +
V IN × f OSC × L
8
×
f
×
C
3
osc
⎝
⎠
inductors lower ripple current and small value inductors result
in high ripple currents. Choose inductor ripple current
Input Zener Selection
approximately 35% of the maximum load current
In USB device application, we will add zener. The zener
600mA, or
ΔI L =210mA.
2008/03/07 Rev. 1.0
can be reduced the surge voltage when device plug in and plug
out. Application circuit is show in Figure3.
Champion Microelectronic Corporation
Page 9
CM3706A
1.5MHz, 600mA Synchronous Step-Down Regulator
PACKAGE DIMENSION
D
5
4
b1
With Plating
c
c1
A
A1
E1
E
A2
b
b
Base Metal
b1
c
Section B-B
c1
D
E
1
e
2
3
e1
E1
b
L
L1
e
θ1
e1
θ
θ1
θ
A2
A
θ2
θ2
A1
L
See Section B-B
L1
Note5: Package outline exclusive of mold flash and metal burr.
2008/03/07 Rev. 1.0
Champion Microelectronic Corporation
Page 10
CM3706A
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
Sales & Marketing
5F, No. 11, Park Avenue II,
Science-Based Industrial Park,
HsinChu City, Taiwan 300
7F-6, No.32, Sec. 1, Chenggong Rd.,
Nangang District, Taipei City 115, Taiwan
T E L : +886-3-567 9979
F A X : +886-3-567 9909
http://www.champion-micro.com
T E L : +886-2-2788 0558
F A X : +886-2-2788 2985
2008/03/07 Rev. 1.0
Champion Microelectronic Corporation
Page 11
Similar pages