NCP1521
1.5 MHz, 600 mA,
High-Ef ficiency, Low
Quiescent Current,
Adjustable Output Voltage
Step-Down Converter
The NCP1521 step- down PWM DC- DC converter is optimized for
portable applications powered from one cell Li- ion or three cell
Alkaline/NiCd/NiMH batteries. The device is available in an adjustable
output voltage from 0.9 V to 3.3 V. It uses synchronous rectification to
increase efficiency and reduce external part count. The device also has a
built- in 1.5 MHz (nominal) oscillator which reduces component size by
allowing a small inductor and capacitors. Automatic switching
PWM/PFM mode offers improved system efficiency.
Finally, it includes an integrated soft-start, cycle-by-cycle current
limiting, and thermal shutdown protection. The NCP1521 is
available in space saving, low profile TSOP5 package.
Features
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MARKING
DIAGRAM
5
5
1
TSOP-5
SN SUFFIX
CASE 483
DBPAYWG
G
1
•
95.3% of Efficiency for 3.3 V Output and 4.2 V Input and 80 mA
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Load-Current
Sources up to 600 mA
1.5 MHz Switching Frequency
Adjustable Output Voltage from 0.9 V to 3.3 V
30
mA
Quiescent Current
Synchronous Rectification for Higher Efficiency
2.7 V to 5.5 V Input Voltage Range
Thermal Limit Protection
Shutdown Current Consumption of 0.3
mA
Short Circuit Protection
This is a Pb-Free Device
Cellular Phones, Smart Phones and PDAs
Digital Still/Video Cameras
MP3 Players and Portable Audio Systems
Wireless and DSL Modems
Portable Equipment
USB Powered Devices
VIN
CIN
2
OFF ON
3
GND
EN
FB
4
R2
L
1
VIN
LX
5
COUT
R1
Cff
VOUT
DBP
= Specific Device Code
A
= Assembly Location
Y
= Year
W
= Work Week
G
= Pb-Free Package
(Note: Microdot may be in either location)
ORDERING INFORMATION
Device
NCP1521ASNT1G
Package
TSOP-5
(Pb-Free)
Shipping
3000/T
ape & Reel
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specification
Brochure, BRD8011/D.
Typical Applications
Figure 1. Typical Application
©
Semiconductor Components Industries, LLC, 2007
1
May, 2007 - Rev. 5
Publication Order Number:
NCP1521/D
NCP1521
100
90
Eff (%)
80
70
V
out
= 3.3 V
V
in
= 4.2 V
T
A
= 25°C
60
50
0
100
200
300
I
out
(mA)
400
500
600
Figure 2. Efficiency vs. Output Current
Q1
Vbattery
Q2
VIN
1
PWM/PFM
CONTROL
LX
5
2.2
mH
10
mF
4.7
mF
GND
2
ILIMIT
R1
18 pF
Enable
EN
3
LOGIC
CONTROL
& THERMAL
SHUTDOWN
REFERENCE
VOLTAGE
FB
4
R2
Figure 3. Simplified Block Diagram
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2
NCP1521
PIN FUNCTION DESCRIPTION
Pin No.
1
2
3
4
5
Symbol
VIN
GND
EN
FB
LX
Function
Analog Input
Analog/Power
Ground
Digital Input
Analog Input
Analog Output
Power Supply Input for Analog V
CC
.
Ground connection for the NFET Power Stage and the Analog Sections of the IC.
Enable for Switching Regulator. This pin is active high. Do not float this pin.
Feedback voltage from the output of the power supply. This is the input to the error
amplifier.
Connection from Power MOSFETs to the Inductor. For one option, an output discharge
circuit sinks current from this pin.
Description
PIN CONNECTIONS
VIN
GND
EN
1
2
3
(Top View)
4
FB
5
LX
Figure 4. Pin Connections
MAXIMUM RATINGS
Rating
Minimum Voltage All Pins
Maximum Voltage All Pins (Note 2)
Maximum Voltage Enable, FB, LX
Thermal Resistance, Junction -to-Air
Operating Ambient Temperature Range
Storage Temperature Range
Junction Operating Temperature
Latch-up Current Maximum Rating (T
A
= 85°C) (Note 4)
ESD Withstand Voltage (Note 3)
Human Body Model
Machine Model
Symbol
V
min
V
max
V
max
R
qJA
T
A
T
stg
T
j
Lu
Vesd
2.0
200
kV
V
Value
-0.3
7.0
VIN + 0.3
300
-40 to 85
-55 to 150
-40 to 125
+/-100
Unit
V
V
V
_C/W
_C
_C
_C
mA
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
1. Maximum electrical ratings are defined as those values beyond which damage to the device may occur at T
A
= 25°C.
2. According to JEDEC standard JESD22-A108B.
3. This device series contains ESD protection and exceeds the following tests:
Human Body Model (HBM) per JEDEC standard: JESD22-A114.
Machine Model (MM) per JEDEC standard: JESD22-A115.
4. Latchup current maximum rating per JEDEC standard: JESD78.
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NCP1521
ELECTRICAL CHARACTERISTICS
(Typical values are referenced to T
A
= +25°C, Min and Max values are referenced -40°C to
+85°C ambient temperature, unless otherwise noted, operating conditions V
IN
= 3.6 V, V
OUT
= 1.8 V, unless otherwise noted.)
Characteristic
Input Voltage Range
Undervoltage Lockout (V
IN
Falling)
Quiescent Current
PFM No Load
Standby Current, EN Low
Oscillator Frequency
Peak Inductor Current
Feedback Reference Voltage
FB Pin Tolerance Overtemp @ I
out
= 100 mA
Reference Voltage Line Regulation
Output Voltage Accuracy @ I
out
= 100 mA (Note 5)
Minimum Output Voltage
Maximum Output Voltage
Output Voltage Line Regulation (V
in
= 2.7–5.5)
Io = 100 mA
Voltage Load Regulation
(IO = 100 mA to 300 mA)
(IO = 100 mA to 600 mA)
Load Transient Response (300 mA to 600 mA Load Step, Trise 10
ms)
Duty Cycle
P-Ch On-Resistance
N-Ch On-Resistance
P-Ch Leakage Current
N-Ch Leakage Current
Enable Pin High
Enable Pin Low
EN << H >> Input Current, EN = 3.6 V
Soft-Start Time
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
Symbol
V
IN
V
UVLO
I
q
Istb
F
osc
I
LIM
V
ref
VFBtol
DVFB
V
OUT
V
OUT
V
OUT
DV
OUT
V
LOADREG
-
-
V
OUT
-
RLxH
RLxL
ILeakH
ILeakL
VENH
VENL
IENH
T
start
T
SD
T
SDH
-
-
-
-
-
-
1.2
-
-
-
-
-
0.0005
0.001
50
-
300
300
0.05
0.01
-
-
2.0
350
160
25
-
-
-
100
-
-
-
-
-
0.4
-
500
-
-
%/mA
%/mA
mV
%
mW
mW
mA
mA
V
V
mA
ms
°C
°C
Min
2.7
2.3
-
-
1.3
-
-
-3.0
-
-3%
-
-
-
Typ
-
2.5
30
0.3
1.5
1200
0.6
-
0.1
Vnom
0.9
3.3
0.1
Max
5.5
2.6
45
1.2
1.8
-
-
3.0
-
+3%
-
-
-
Unit
V
V
mA
mA
MHz
mA
V
%
%
V
V
V
%
5. The overall output voltage tolerance depends upon the accuracy of the external resistor (R1, R2).
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NCP1521
100
90
QUIESCENT CURRENT (mA)
QUIESCENT CURRENT (mA)
80
70
60
50
40
30
20
10
0
2.7
3.2
3.7
4.2
4.7
EN = V
IN
I
OUT
= 0 mA
5.2
5.7
100
90
80
70
60
50
40
30
20
10
0
-40
-20
0
20
40
60
80
100
V
IN
= 2.7 V
V
IN
= 5.5 V
V
IN
, INPUT VOLTAGE (V)
TEMPERATURE (°C)
Figure 5. Quiescent Current vs. Supply Voltage
Figure 6. Quiescent Current vs. Temperature
1.0
EN = V
IN
SHUTDOWN CURRENT (mA)
0.8
I
OUT
= 0 mA
EFFICIENCY (%)
100
95
T
A
= -40°C
90
85
80
75
70
3.2
3.7
4.2
4.7
0
100
200
300
400
500
600
V
IN
, INPUT VOLTAGE (V)
I
OUT
, OUTPUT CURRENT (mA)
T
A
= 85°C
T
A
= 25°C
0.6
0.4
0.2
0
2.7
Figure 7. Shutdown Current vs. Supply Voltage
Figure 8. Efficiency vs. Output Current
(V
OUT
= 1.8 V, V
IN
= 3.6 V)
100
T
A
= -40°C
T
A
= 25°C
EFFICIENCY (%)
100
95
90
T
A
= 25°C
85
80
75
70
0
100
200
300
400
500
600
0
100
200
300
400
500
600
I
OUT
, OUTPUT CURRENT (mA)
I
OUT
, OUTPUT CURRENT (mA)
T
A
= 85°C
T
A
= -40°C
90
EFFICIENCY (%)
80
70
T
A
= 85°C
60
50
Figure 9. Efficiency vs. Output Current
(V
OUT
= 0.9 V, V
IN
= 3.6 V)
Figure 10. Efficiency vs. Output Current
(V
OUT
= 3.3 V, V
IN
= 4.5 V)
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