Datasheet

UNISONIC TECHNOLOGIES CO., LTD
USR1021
Preliminary
LINEAR INTEGRATED CIRCUIT
3A SYNCHRONOUS BUCK
REGULATOR

DESCRIPTION
The UTC USR1021 is a high efficiency, 3A synchronous buck
regulator. The UTC USR1021 works from a 6V to 18V input
voltage range, and provides up to 3A of continuous output current
with an output voltage adjustable down to 0.8V.
The UTC USR1021 comes in an SOP-8 packages and is rated
over a -40°C~+85°C ambient temperature range.

SOP-8
FEATURES
* 6V~18V operating input voltage range
* High efficiency
* Internal soft start
* 1.5% initial output accuracy
* Output voltage adjustable to 0.8V
* 3A continuous output current
* Cycle-by-cycle current limit
* 500kHz PWM operation
* Thermal shutdown
* Short-circuit protection

ORDERING INFORMATION
Ordering Number
Lead Free
Halogen Free
USR1021L-S08-R
USR1021G-S08-R
USR1021L-S08-T
USR1021G-S08-T
Note: xx: Output Voltage, refer to Marking Information.
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Copyright © 2013 Unisonic Technologies Co., Ltd
Package
Packing
SOP-8
SOP-8
Tape Reel
Tube
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USR1021
Preliminary

PIN CONFIGURATION

PIN DESCRIPTION
PIN NO.
1
2
3
4
5
6
7, 8

PIN NAME
PGND
VIN
AGND
FB
COMP
EN
LX
LINEAR INTEGRATED CIRCUIT
DESCRIPTION
Power ground
Supply voltage input
Reference connectio for controller section
Feedback voltage
Compensation pin
Enable pin
Switch pin
BLOCK DIAGRAM
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QW-R103-073.a
USR1021

Preliminary
LINEAR INTEGRATED CIRCUIT
ABSOLUTE MAXIMUM RATING
PARAMETER
SYMBOL
RATINGS
UNIT
Supply Voltage
VIN
18
V
LX to AGND
-0.7~VIN+0.3
V
EN to AGND
-0.3~VIN+0.3
V
FB to AGND
-0.3~6.0
V
COMP to AGND
-0.3~6.0
V
PGND to AGND
-0.3~+0.3
V
Junction Temperature
TJ
+150
°C
Storage Temperature
TSTG
-65~+150
°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.

THERMAL DATA
PARAMETER
Junction to Ambient (Note 2)

RATINGS
87
UNIT
°С/W
RATINGS
6~18
0.8~VIN
-40~+85
UNIT
V
V
°C
RECOMMENDED OPERATING CONDIIONS
PARAMETER
Supply Voltage
Output Voltage Range
Ambient Temperature

SYMBOL
θJA
SYMBOL
VIN
TA
ELECTRICAL CHARACTERISTICS
(TA=25°C, VIN=VEN=12V, VOUT=3.3V, unless otherwise specified) (Note 3)
PARAMETER
Supply Voltage
Supply Current (Quiescent)
Shutdown Supply Current
Feedback Voltage
Load Regulation
Line Regulation
Feedback Voltage Input Current
EN Input Threshold
SS Time
MODULATOR
Frequency
Maximum Duty Cycle
Controllable Minimum On Time
Current Sense Transconductance
Error Amplifier Transconductance
PROTECTION
Current Limit
SYMBOL
VIN
IIN
IOFF
VFB
TEST CONDITIONS
IOUT=0, VFB=1.2V, VEN>2V
VEN=0V
TA=25 °C
MIN
6
0.788
TYP
3.5
1
0.8
0.5
1
IFB
VEN
fO
DMAX
TMIN
Off Threshold
On Threshold
CSS=16nF
2
2
400
85
500
MAX UNIT
18
V
5
mA
10
µA
0.812
V
%
%
200
nA
0.6
V
V
ms
600
150
7
180
kHz
%
ns
A/V
µA/V
ILIMT
3.5
4.5
A
150
°C
TJ Rising
Over-Temperature Shutdown Limit
TJ Falling
100
°C
Notes: 1. Devices are inherently ESD sensitive, handling precautions are required. Human body model rating: 1.5
kΩ in series with 100pF.
2. The value of θJA is measured with the device mounted on a 1-in2 FR-4 board with 2oz. Copper, in a still air
environment with TA=25°C. The value in any given application depends on the user’s specific board
design.
3. Specification in BOLD indicate an ambient temperature range of -40°C~+85°C. These specifications are
guaranteed by design.
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USR1021

Preliminary
LINEAR INTEGRATED CIRCUIT
TYPICAL APPLICATION CIRCUIT
VIN
C1
22µF
Ceramic
VIN
L1 4.7µH
EN
COMP
UTC USR1021
RC
CC
VOUT
LX
R1
FB
AGND
PGND
C2, C3
22µF
Ceramic
R2
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.
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