Datasheet

UNISONIC TECHNOLOGIES CO., LTD
UC3655
CMOS IC
500mA SYNCHRONOUS
STEP-DOWN DC/DC
CONVERTERS

DESCRIPTION
The UTC UC3655 is a synchronous-rectification type DC/DC
converters with a built-in 0.6Ω P-channel driver transistor and 0.7Ω
N-channel switching transistor, which designed to allow the use of
ceramic capacitors. Using only a coil and two capacitors connected
externally, the UC3655 enable a high efficiency, stable power supply
with an output current of 500mA to be configured. Its operating voltage
is 2.0V and the output voltage is programmable in a range from 0.9V to
4.0V in increments of 0.1V (accuracy: ±2.0%) internally. The oscillation
frequency is 1.3MHz.
For operation mode, it is PWM control in the UTC UC3655, the UTC
UC3655 series is automatic PWM/PFM switching control, allowing fast
response, low ripple and high efficiency over the full range of load.
Internal soft start and current control functions are built in it. All
circuits are shutdown to reduce current consumption to as low as 1.0μA
or less during standby mode. With the built-in Under Voltage Lock Out
(U.V.L.O.) function, when input voltage becomes 1.4V or lower the
internal P channel driver transistor is forced OFF.

FEATURES
* Very High Efficiency 92%
* Low Ripple Rejection Voltage 10mV
* Output Current 500mA @VIN=3.0V, VOUT=1.8V
* Oscillation Frequency is 1.3MHz
* With PWM / PFM Automatic Switching Control
* Maximum Duty Ratio is 100%
* Ceramic Capacitor Available

ORDERING INFORMATION
Ordering Number
Lead Free
Halogen Free
UC3655L-xx-AF5-R
UC3655G-xx-AF5-R
www.unisonic.com.tw
Copyright © 2014 Unisonic Technologies Co., Ltd
Package
Packing
SOT-25
Tape Reel
1 of 9
QW-R502-280.F
UC3655

CMOS IC
MARKING
PACKAGE
VOLTAGE CODE
SOT-25
12:1.2V
28:2.8V
33:3.3V
38:3.8V
MARKING
4
5
Voltage Code
UHXXG
1

3
PIN DESCRIPTION
PIN NO
1
2
3
4
5

2
G: Halogen Free
L: Lead Free
PIN NAME
VIN
VSS
CE / MODE
VOUT
Lx
DESCRIPTION
Power Input Voltage
Ground
Switch Pin For Chip Enable Mode
Output Voltage Sense Pin
Output Of Switching
BLOCK DIAGRAM
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www.unisonic.com.tw
2 of 9
QW-R502-280.F
UC3655

CMOS IC
ABSOLUTE MAXIMUM RATING (TA=25°C, unless otherwise specified)
PARAMETER
SYMBOL
RATINGS
UNIT
VIN
- 0.3 ~ 6.5
V
LX
VLx
- 0.3 ~ VIN + 0.3
Input/Output Pins
VOUT
VOUT
-0.3 ~ 6.5
V
CE/MODE
VCE
- 0.3 ~ VIN + 0.3
Lx Pin Current
ILX
±1000
mA
Power Dissipation
PD
250
mW
Operating Temperature
TOPR
- 40 ~ 85
°C
Storage Temperature Range
TSTG
- 55 ~ 125
°C
Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged.
Absolute maximum ratings are stress ratings only and functional device operation is not implied.
VIN Pin Voltage

ELECTRICAL CHARACTERISTICS (fOSC=1.2MHz, TA=25°C, unless otherwise specified)
UC3655-12 (VIN=3.6V, VOUT=1.2V)
PARAMETER
SYMBOL
Operating Voltage Range
VIN
Output Voltage
VOUT
U.V.L.O. Voltage
VUVLO
∆VOUT
Output Voltage Temperature
Characteristics
VOUT*∆TOPR
Maximum Output Current
IOUT(MAX)
Supply Current
IDD
Stand-by Current
ISTN-BY
PFM Switch Current
IPFM
Current Limit
ILIM
Efficiency (Note 1)
η
OSCILLATOR
Oscillation Frequency
fOSC
Maximum Duty Ratio
DMAX
Minimum Duty Ratio
DMIN
Soft-Start Time
TSS
Latch Time
TLAT
CE (PIN 3)
CE "H" Voltage
VCEH
CE "L" Voltage
VCEL
CE "H" Current
ICEH
CE "L" Current
ICEL
LX (PIN 5)
LX SW "H" ON Resistance
RLXH
LX SW "L" ON Resistance
RLXL
LX SW "H" Leak Current (Note 2)
ILEAKH
LX SW "L" Leak Current
ILEAKL
TEST CONDITIONS
CE=VIN, IOUT=30mA
CE=VIN, VOUT=0V, LX=L
IOUT=30mA, -40°C ≤TOPR≤85°C
VIN=4.5V
VIN=CE=5.0V, VOUT=VOUT*1.1
VIN=5.0V, CE=0V, VOUT=VOUT*1.1
CE=VIN, IOUT=1mA
VIN=CE=5.0V, VOUT=0V
CE=VIN=4.5V, IOUT=100mA
IOUT=100mA
CE=VIN, VOUT=0V
CE=VOUT=VIN
IOUT=1mA
VIN=CE=5.0V (Note 3)
VIN=CE=5.5V, VOUT=0V
VIN=5.5V, CE=0V, VOUT=0V
CE=0.5VIN, VOUT=0V, ILX=100mA
CE=0.5VIN, ILX=100mA
VIN=VOUT=5.0V, CE=0V, LX=0V
VIN=VOUT=5.0V, CE=0V, LX=5.0V
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
MIN
2.0
1.176
1.0
TYP
1.200
1.40
MAX
6.0
1.224
1.78
±100
UNIT
V
V
V
ppm/°C
500
mA
µA
µA
mA
mA
%
70
0
140
700
90
115
1.0
180
1020
100
1300
1500
0.5
1
1.0
0
3.0
20
kHz
%
%
ms
ms
VIN
0.3
0.1
0.1
V
V
µA
µA
1.0
1.0
Ω
Ω
µA
µA
100
600
0.9
VSS
-0.1
-0.1
0.6
0.7
0.01
0.01
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QW-R502-280.F
UC3655

CMOS IC
ELECTRICAL CHARACTERISTICS(Cont.)
UC3655-28 (VIN=3.6V, VOUT=2.8V)
PARAMETER
SYMBOL
Operating Voltage Range
VIN
Output Voltage
VOUT
U.V.L.O. Voltage
VUVLO
∆VOUT
Output Voltage Temperature
Characteristics
VOUT*∆TOPR
Maximum Output Current
IOUT(MAX)
Supply Current
IDD
Stand-by Current
ISTN-BY
PFM Switch Current
IPFM
Current Limit
ILIM
Efficiency (Note 1)
η
OSCILLATOR
Oscillation Frequency
fOSC
Maximum Duty Ratio
DMAX
Minimum Duty Ratio
DMIN
Soft-Start Time
TSS
Latch Time
TLAT
CE (PIN 3)
CE "H" Voltage
VCEH
CE "L" Voltage
VCEL
CE "H" Current
ICEH
CE "L" Current
ICEL
LX (PIN 5)
LX SW "H" ON Resistance
RLXH
LX SW "L" ON Resistance
RLXL
LX SW "H" Leak Current
ILEAKH
LX SW "L" Leak Current
ILEAKL
UC3655-33 (VIN=5.0V, VOUT=3.3V)
PARAMETER
SYMBOL
Operating Voltage Range
VIN
Output Voltage
VOUT
U.V.L.O. Voltage
VUVLO
∆VOUT
Output Voltage Temperature
Characteristics
VOUT*∆TOPR
Maximum Output Current
IOUT(MAX)
Supply Current
IDD
Stand-by Current
ISTN-BY
PFM Switch Current
IPFM
Current Limit
ILIM
Efficiency (Note 1)
η
OSCILLATOR
Oscillation Frequency
fOSC
Maximum Duty Ratio
DMAX
Minimum Duty Ratio
DMIN
Soft-Start Time
TSS
Latch Time
TLAT
TEST CONDITIONS
CE=VIN, IOUT=30mA
CE=VIN, VOUT=0V, LX=L
IOUT=30mA, -40°C ≤TOPR≤85°C
VIN=4.5V
VIN=CE=5.0V, VOUT=VOUT*1.1
VIN=5.0V, CE=0V, VOUT=VOUT*1.1
CE=VIN, IOUT=1mA
VIN=CE=5.0V, VOUT=0V
CE=VIN=4.5V, IOUT=100mA
IOUT=100mA
CE=VIN, VOUT=0V
CE=VOUT=VIN
IOUT=1mA
VIN=CE=5.0V (Note 3)
VIN=CE=5.5V, VOUT=0V
VIN=5.5V, CE=0V, VOUT=0V
TEST CONDITIONS
CE=VIN, IOUT=30mA
CE=VIN, VOUT=0V, LX=L
IOUT=100mA
CE=VIN, VOUT=0V
CE=VOUT=VIN
IOUT=1mA
VIN=CE=5.0V (Note 3)
2.8
1.40
MAX
6.0
2.856
1.78
UNIT
V
V
V
ppm/°C
75
0
140
700
92
120
1.0
180
mA
µA
µA
mA
mA
%
1020
100
1300
1500
0.5
1
1.0
0
3.0
20
kHz
%
%
ms
ms
VIN
0.3
0.1
0.1
V
V
µA
µA
500
100
600
0.9
VSS
-0.1
-0.1
0.5
0.6
MIN
2.0
3.234
1.0
IOUT=30mA, -40℃≤TOPR≤85℃
VIN=4.5V
VIN=CE=5.0V, VOUT=VOUT*1.1
VIN=5.0V, CE=0V, VOUT=VOUT*1.1
CE=VIN, IOUT=1mA
VIN=CE=5.0V, VOUT=0V
CE=VIN=4.5V, IOUT=100mA
TYP
±100
CE=0.5VIN, VOUT=0V, ILX=100mA
CE=0.5VIN, ILX=100mA
VIN=VOUT=5.0V, CE=0V, LX=0V
(Note 2)
VIN=VOUT=5.0V, CE=0V, LX=5.0V
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
MIN
2.0
2.744
1.0
Ω
Ω
0.01
1.0
µA
0.01
1.0
µA
TYP
MAX
6.0
3.366
1.78
UNIT
V
V
V
3.300
1.40
±100
ppm/°C
500
75
0
140
700
92
120
1.0
180
1020
100
1300
1500
0.5
1
1.0
0
3.0
20
100
600
mA
µA
µA
mA
mA
%
kHz
%
%
ms
ms
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QW-R502-280.F
UC3655

CMOS IC
ELECTRICAL CHARACTERISTICS(Cont.)
PARAMETER
CE (PIN 3)
CE "H" Voltage
CE "L" Voltage
CE "H" Current
CE "L" Current
LX (PIN 5)
LX SW "H" ON Resistance
LX SW "L" ON Resistance
LX SW "H" Leak Current (Note 2)
LX SW "L" Leak Current
SYMBOL
TEST CONDITIONS
MIN
VCEH
VCEL
ICEH
ICEL
VIN=CE=5.5V, VOUT=0V
VIN=5.5V, CE=0V, VOUT=0V
0.9
VSS
-0.1
-0.1
RLXH
RLXL
ILEAKH
ILEAKL
CE=0.50VIN, VOUT=0V, ILX=100mA
CE=0.5VIN, ILX=100mA
VIN=VOUT=5.0V, CE=0V, LX=0V
VIN=VOUT=5.0V, CE=0V, LX=5.0V
TYP
0.5
0.6
0.01
0.01
MAX
UNIT
VIN
0.3
0.1
0.1
V
V
µA
µA
1.0
1.0
Ω
Ω
µA
µA
UC3655-38 (VIN=5.0V, VOUT=3.8V)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP MAX UNIT
Operating Voltage Range
VIN
2.0
6.0
V
Output Voltage
VOUT
CE=VIN, IOUT=30mA
3.724 3.800 3.876
V
U.V.L.O. Voltage
VUVLO
CE=VIN, VOUT=0V, LX=L
1.0
1.40
1.78
V
∆VOUT
Output Voltage Temperature
IOUT=30mA, -40℃≤TOPR≤85℃
±100
ppm/°C
Characteristics
VOUT*∆TOPR
Maximum Output Current
IOUT(MAX)
VIN=4.5V
500
mA
Supply Current
IDD
VIN=CE=5.0V, VOUT=VOUT*1.1
75
120
µA
Stand-by Current
ISTN-BY
VIN=5.0V, CE=0V, VOUT=VOUT*1.1
0
1.0
µA
PFM Switch Current
IPFM
CE=VIN, IOUT=1mA
100
140
180
mA
Current Limit
ILIM
VIN=CE=5.0V, VOUT=0V
600
700
mA
Efficiency (Note 1)
η
CE=VIN=4.5V, IOUT=100mA
92
%
OSCILLATOR
Oscillation Frequency
fOSC
IOUT=100mA
1020 1300 1500
kHz
Maximum Duty Ratio
DMAX
CE=VIN, VOUT=0V
100
%
Minimum Duty Ratio
DMIN
CE=VOUT=VIN
0
%
Soft-Start Time
TSS
IOUT=1mA
0.5
1.0
3.0
ms
Latch Time
TLAT
VIN=CE=5.0V (Note 3)
1
20
ms
CE (PIN 3)
CE "H" Voltage
VCEH
0.9
VIN
V
CE "L" Voltage
VCEL
VSS
0.3
V
CE "H" Current
ICEH
VIN=CE=5.5V, VOUT=0V
-0.1
0.1
µA
CE "L" Current
ICEL
VIN=5.5V, CE=0V, VOUT=0V
-0.1
0.1
µA
LX (PIN 5)
LX SW "H" ON Resistance
RLXH
CE=0.5VIN, VOUT=0V, ILX=100mA
0.5
Ω
LX SW "L" ON Resistance
RLXL
CE=0.5VIN, ILX=100mA
0.6
Ω
LX SW "H" Leak Current (Note 2)
ILEAKH
VIN=VOUT=5.0V, CE=0V, LX=0V
0.01
1.0
µA
LX SW "L" Leak Current
ILEAKL
VIN=VOUT=5.0V, CE=0V, LX=5.0V
0.01
1.0
µA
Note: 1. η= [(VOUT*IOUT)/(VIN*IIN)]*100
Note: 2. When temperature is high, a current of approximately 20μA (maximum) may leak.
Note: 3. Time until it short-circuits DCOUT with GND through 1Ω of resistance from a state of operation and is set to
DCOUT=0V from current limit pulse generating.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
5 of 9
QW-R502-280.F
UC3655

CMOS IC
OPERATIONAL EXPLANATION
CE / MODE Pin Function
When a low level signal is input to the CE/MODE pin the operation of the UC3655 series will enter into the shut down
mode. In this mode, the current consumption occurs only in the detector and is 0 μA (TYP.), with a state of high
impedance at the Lx pin and VOUT pin. By inputting a high level signal to the CE/MODE pin the IC starts its
operation. The input of the CE/MODE pin is a CMOS input and its sink current is 0 μA (TYP.).
UC3655 series - Examples of how to use CE/MODE pin
VIN
VDD
R1
SW_CE

CE/MODE
SW_CE
ON
OFF
STATUS
Stand-by
Operation
SW_CE
ON
OFF
STATUS
Operation
Stand-by
FUNCTIONS
CE/MODE
H Level
M Level
L Level
VOLTAGE LEVEL
VIN-0.3V≦H level≦VIN
0.9V≦M Level≦VIN-1.0V
0V≦L Level≦0.3V
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
OPERATION
Synchronous PWM/PFM Automatic Switching Control
Stand-by
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QW-R502-280.F
UC3655

CMOS IC
TEST CIRCUIT
CI
CL
L
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
4.7µF (Ceramic)
10µF (Ceramic)
3.3µH
7 of 9
QW-R502-280.F
UC3655

CMOS IC
TYPICAL APPLICATION CIRCUIT
VIN
CI
CE/MODE
LX
VIN
CE/
MODE VSS
CI
CL
L
VOUT
(400mA)
CL
VOUT
4.7µF (Ceramic)
10µF (Ceramic)
3.3µH
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
L
8 of 9
QW-R502-280.F
UC3655

CMOS IC
TYPICAL CHARACTERISTICS
Transfer Response
IO=250~500mA
Lx: CH1: SW, CH2: VO, CH3: IO=100mA
CH1: 200mV/div
CH2: 250mA/div
CH1: 2V/div
CH2: 20mV/div
CH3: 250mA/div
CH1
0
0
CH2
CH1
0
CH2
0
CH3
0
0
2000
Time (400ns/div)
4000
0
1000
Time (200µs/div)
2000
UTC assumes no responsibility for equipment failures that result from using products at values that
exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or
other parameters) listed in products specifications of any and all UTC products described or contained
herein. UTC products are not designed for use in life support appliances, devices or systems where
malfunction of these products can be reasonably expected to result in personal injury. Reproduction in
whole or in part is prohibited without the prior written consent of the copyright owner. The information
presented in this document does not form part of any quotation or contract, is believed to be accurate
and reliable and may be changed without notice.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
9 of 9
QW-R502-280.F
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