CHAMP CM3708AIS 3a low-noise pwm step-down regulator Datasheet

CM3708A
3A LOW-NOISE PWM STEP-DOWN REGULATOR
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.
‹
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
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.
External Soft Start
Rail to Rail output Buck Converter
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 5.5V. Other features of the CM3708A include high
efficiency, low dropout voltage. It is available in a
space-saving 16-pin SOP & TSSOP package.
APPLICATIONS
‹
Cellular Phone
‹
CPU I/O Supplies
‹
Cordless Phone
‹
Notebook Chipset Supplies
‹
PDAs and Handy-Terminals
‹
Battery Operated Devices
‹
AGP Chipset Supplies
PIN CONFIGURATION
PSOP-16 (PS16) / PTSSOP-16 (PT16)
Top View
2007/02/13 Rev1.3
1
VIN1
VIN2
16
2
PVIN1
PVIN2
15
3
LX1
LX2
14
4
PGND1
PGND2
13
5
AGND
AGND
12
6
SD
VFB
11
7
VREF
NC
10
8
AGSEN
AGND
9
Champion Microelectronic Corporation
Page 1
CM3708A
3A LOW-NOISE PWM STEP-DOWN REGULATOR
PIN DESCRIPTION
Pin No.
Symbol
Description
Min.
Operating Rating
Typ.
Max.
Unit
1,16
VIN1, VIN2
Voltage supply for internal circuits
2
2.5
5.5
V
2,15
PVIN1, PVIN2
Voltage supply for output power transistors
2
2.5
5.5
V
3,14
LX1, LX2
Inductor connection to the Drains of the internal
5
V
0.75 x
VIN +
V
VIN
0.3V
0
VIN
V
5
V
power MOSFETs
4,13
PGND1, PGND2
Ground for output power transistors
AGND
Ground for internal reference voltage divider
8
AGSEN
Ground for remote sensing
6
SD
Shutdown active high. CMOS input level
5,9,12
7
VREF
VOUT Set Voltage
10
NC
No Connection
11
VFB
Feedback node for the VOUT
BLOCK DIAGRAM
AGND
5
AGND
9
NC
VIN1
VIN2
SD
PVIN1
PVIN2
10
1
16
6
2
15
Oscillator Ramp Generator
AGND
12
PW M Controller
VREF
Error Amp
7
2007/02/13 Rev1.3
8
11
AGSEN
VFB
MOS
3
LX1
14
LX2
Therm al
Protection
4
PGND1
13
PGND2
Champion Microelectronic Corporation
Page 2
CM3708A
3A LOW-NOISE PWM STEP-DOWN REGULATOR
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
Absolute maximum ratings are those values beyond which the
Junction Temperature ...…………………… …………150°C
device could be permanently damaged.
Storage Temperature
PVIN/VIN …………......................................….......-0.3V to 6.0V
Lead Temperature (Soldering, 5 sec)……………….. 260°C
Thermal Dissipation(θJC )….. ………………….. .50°C/W
Voltage on Any Other Pin ………... GND – 0.3V to VIN + 0.3V
……................……. -65°C to 125°C
Output Current, Source or Sink ……......…………........…...3.0A
OPERATING CONDITIONS
Temperature Range ............................. -40°C to 85°C
PVIN Operating Range .........................2.0V to 5.5V
ELECTRICAL CHARACTERISTICS
(Unless otherwise stated, these specifications apply TA=25°C;
VIN=+3.3V and PVIN=+3.3V) maximum ratings are stress ratings only and functional device operation is not implied.
(Note 1)
Symbol
Parameter
Test Conditions
CM3708A
Min.
Typ.
Max.
Unit
SWITCHING REGULATOR
VREF
Adjustable Output Voltage
0
VIN
V
480
fsw
Switching Frequency
CM3708A
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
Drain to Source on-State Resistance
PVIN=5V
150
A
MOSFETs
RDS(ON)
180
mΩ
SUPPLY
IVIN
Quiescent Current
IPVIN
Quiescent Current
VFB = 1.4V
LC unconnected
VFB = 1.4V
LC unconnected
200
μA
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
2007/02/13 Rev1.3
Champion Microelectronic Corporation
Page 3
CM3708A
3A LOW-NOISE PWM STEP-DOWN REGULATOR
FUNCTIONAL DESCRIPTION
The CM3708A step-down, pulse-width-modulated (PWM), INPUTS
DC-DC converter has an adjustable output range from VREF The input voltage reference pin, VREF determine the output
to the input voltage (VIN). An internal synchronous rectifier voltages (LX1, LX2). If a specific voltage is forced at the VREF
improves efficiency and eliminates an external Schottky diode. pin, the output voltage follows the voltage at the VREF pin.
Fixed-frequency operation enables easy post-filtering, thereby
providing excellent noise characteristics. As a result, the OTHER SUPPLY VOLTAGES
CM3708A is an ideal choice for many small wireless systems.
Several inputs are provided for the supply voltages: PVIN and
VIN.
VREF
The PVIN provide the power supply to the power MOSFETs.
The reference voltage could be ranged from 0V to VIN.
VIN provides the voltage supply to the logic section and internal
error amplifiers.
OUPUTS
The output voltage pins (LX1, LX2) are tied to the RF power
amp, via an external inductor. Output voltage is determined by FEEDBACK
the VREF inputs so it can be from 0V to VIN.
The VFB pin is an input that can be used for closed loop
Internal Power Switches:
compensation. This input is derived from the voltage output.
CM3708A has been integrated 2 Power MOSFETs whose
AGND pin is a contact node of internal resistor divider for
RDS(ON) is around 100m Ohm each.
remote sense.
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.
APPLICATION CIRCUIT
L1
3.3uH
Vout
J1
1
2
C2
104
C1
220uf/6.3V
VIN
10uf/6.3V
C4
104
C3
1
PVIN
2
3
C6
100uf/6.3V
C7
104
4
5
6
VREF
7
8
U1 CM3708A
VIN1
PVIN1
LX1
VIN2
PVIN2
LX2
PGND1 PGND2
AGND
SD
VREF
AGSEN
AGND
VFB
NC
AGND
VIN
16
13
J2
DC-INPUT
PVIN
1
2
PVIN
15
14
R1
5R1
C8
104
C9
104
12
C5
C10
100uf/6.3V
470uf/6.3V
11
10
9
C11
104
R2 200k
1
2
1
2
R3
1k
2007/02/13 Rev1.3
C12
102
Champion Microelectronic Corporation
Page 4
CM3708A
3A LOW-NOISE PWM STEP-DOWN REGULATOR
PACKAGE DIMENSION
16-PIN PTSSOP (PT16)
16-PIN PSOP (PS16)
θ
θ
2007/02/13 Rev1.3
Champion Microelectronic Corporation
Page 5
CM3708A
3A 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
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
2007/02/13 Rev1.3
Champion Microelectronic Corporation
Page 6
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