NCP1421
600 mA Sync−Rect PFM
Step−Up DC−DC Converter
with True−Cutoff and
Ring−Killer
NCP1421 is a monolithic micropower high−frequency step−up
switching converter IC specially designed for battery−operated
hand−held electronic products up to 600 mA loading. It integrates
Sync−Rect to improve efficiency and to eliminate the external
Schottky Diode. High switching frequency (up to 1.2 MHz) allows
for a low profile, small−sized inductor and output capacitor to be
used. When the device is disabled, the internal conduction path from
LX or BAT to OUT is fully blocked and the OUT pin is isolated from
the battery. This True−Cutoff function reduces the shutdown current
to typically only 50 nA. Ring−Killer is also integrated to eliminate
the high−frequency ringing in discontinuous conduction mode. In
addition to the above, Low−Battery Detector, Logic−Controlled
Shutdown, Cycle−by−Cycle Current Limit and Thermal Shutdown
provide value−added features for various battery−operated
applications. With all these functions on, the quiescent supply
current is typically only 8.5
mA.
This device is available in the
compact and low profile Micro8t package.
Features
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MARKING
DIAGRAM
Micro8
DM SUFFIX
CASE 846A
8
1
1421
AYW
1421
A
Y
W
= Device Code
= Assembly Location
= Year
= Work Week
•
Pb−Free Package is Available
•
High Efficiency: 94% for 3.3 V Output at 200 mA from 2.5 V Input
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
88% for 3.3 V Output at 500 mA from 2.5 V Input
High Switching Frequency, up to 1.2 MHz (not hitting current limit)
Output Current up to 600 mA at V
IN
= 2.5 V and V
OUT
= 3.3 V
True−Cutoff Function Reduces Device Shutdown Current to
typically 50 nA
Anti−Ringing Ring−Killer for Discontinuous Conduction Mode
High Accuracy Reference Output, 1.20 V
$1.5%,
can Supply
2.5 mA Loading Current when V
OUT
> 3.3 V
Low Quiescent Current of 8.5
mA
Integrated Low−Battery Detector
Open Drain Low−Battery Detector Output
1.0 V Startup at No Load Guaranteed
Output Voltage from 1.5 V to 5.0 V Adjustable
1.5 A Cycle−by−Cycle Current Limit
Multi−function Logic−Controlled Shutdown Pin
On Chip Thermal Shutdown with Hysteresis
FB
LBI/EN
LBO
REF
PIN CONNECTIONS
1
2
3
4
(Top View)
8
7
6
5
OUT
LX
GND
BAT
ORDERING INFORMATION
Device
NCP1421DMR2
NCP1421DMR2G
Package
Micro8
Micro8
(Pb−Free)
Shipping†
4000 Tape & Reel
4000 Tape & Reel
Typical Applications
Personal Digital Assistants (PDA)
Handheld Digital Audio Products
Camcorders and Digital Still Cameras
Hand−held Instruments
Conversion from one to two Alkaline, NiMH, NiCd Battery Cells to
3.0−5.0 V or one Lithium−ion cells to 5.0 V
•
White LED Flash for Digital Cameras
©
Semiconductor Components Industries, LLC, 2004
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specifications
Brochure, BRD8011/D.
1
October, 2004 − Rev. 6
Publication Order Number:
NCP1421/D
NCP1421
V
BAT
M3
BAT
5
ZLC
0.5 V
Chip
Enable
+
−
+
20 mV
TRUE CUTOFF
CONTROL
V
DD
LX
V
DD
7
OUT
M2
SENSEFETt
V
OUT
CONTROL LOGIC
_ZCUR
_MSON
_MAINSW2ON
_TSDON
8
M1
6
GND
V
DD
GND
FB
1
_CEN
+
−
_PFM
PFM
_MAINSWOFD
_SYNSW2ON
REF
4
Voltage
Reference
_SYNSWOFD
_V
REFOK
_ILIM
+
−
GND
+
GND
R
SENSE
LBO
3
1.20 V
LBI/EN
2
+
−
GND
Figure 1. Detailed Block Diagram
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2
NCP1421
PIN FUNCTION DESCRIPTIONS
Pin
1
2
3
4
5
6
7
8
Symbol
FB
LBI/EN
LBO
REF
BAT
GND
LX
OUT
Output Voltage Feedback Input.
Low−Battery Detector Input and IC Enable. With this pin pulled down below 0.5 V, the device is disabled and
enters the shutdown mode.
Open−Drain Low−Battery Detector Output. Output is LOW when V
LBI
is < 1.20 V. LBO is high impedance in
shutdown mode.
1.20 V Reference Voltage Output, bypass with 1.0
mF
capacitor. If this pin is not loaded, bypass with 300 nF
capacitor; this pin can be loaded up to 2.5 mA @ V
OUT
= 3.3 V.
Battery input connection for internal ring−killer.
Ground.
N−Channel and P−Channel Power MOSFET drain connection.
Power Output. OUT also provides bootstrap power to the device.
Description
MAXIMUM RATINGS
(T
C
= 25°C unless otherwise noted.)
Rating
Power Supply (Pin 8)
Input/Output Pins (Pin 1−5, Pin 7)
Thermal Characteristics
Micro8 Plastic Package
Thermal Resistance Junction−to−Air
Operating Junction Temperature Range
Operating Ambient Temperature Range
Storage Temperature Range
P
D
R
qJA
T
J
T
A
T
stg
520
240
−40 to +150
−40 to +85
−55 to +150
mW
_C/W
_C
_C
_C
Symbol
V
OUT
V
IO
Value
−0.3, 5.5
−0.3, 5.5
Unit
V
V
Maximum ratings are those values beyond which device damage can occur. Maximum ratings applied to the device are individual stress limit values
(not normal operating conditions) and are not valid simultaneously. If these limits are exceeded, device functional operation is not implied, damage
may occur and reliability may be affected.
1. This device contains ESD protection and exceeds the following tests:
Human Body Model (HBM)
±2.0
kV per JEDEC standard: JESD22−A114. *Except OUT pin, which is 1k V.
Machine Model (MM)
±200
V per JEDEC standard: JESD22−A115. *Except OUT pin, which is 100 V.
2. The maximum package power dissipation limit must not be exceeded.
TJ(max)
*
TA
PD
+
R
qJA
3. Latchup Current Maximum Rating:
±150
mA per JEDEC standard: JESD78.
4. Moisture Sensitivity Level: MSL 1 per IPC/JEDEC standard: J−STD−020A.
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3
NCP1421
ELECTRICAL CHARACTERISTICS
(V
OUT
= 3.3 V, T
A
= 25°C for typical value, −40°C
v
T
A
v
85°C for min/max values unless
otherwise noted.)
Characteristic
Operating Voltage
Output Voltage Range
Reference Voltage
(V
OUT
= 3.3 V, I
LOAD
= 0
mA,
C
REF
= 200 nF, T
A
= 25°C)
Reference Voltage
(V
OUT
= 3.3 V, I
LOAD
= 0
mA,
C
REF
= 200 nF, T
A
= −40°C to 85°C)
Reference Voltage Temperature Coefficient
Reference Voltage Load Current
(V
OUT
= 3.3 V, V
REF
= V
REF_NL
"1.5%
C
REF
= 1.0
mF)
(Note 5
)
Reference Voltage Load Regulation
(V
OUT
= 3.3 V, I
LOAD
= 0 to 100
mA,
C
REF
= 1.0
mF)
Reference Voltage Line Regulation
(V
OUT
from 1.5 V to 5.0 V, C
REF
= 1.0
mF)
FB Input Threshold (I
LOAD
= 0 mA, T
A
= 25°C)
FB Input Threshold (I
LOAD
= 0 mA, T
A
= −40°C to 85°C)
LBI Input Threshold (I
LOAD
= 0 mA, T
A
= −40_C to 85_C)
LBI Input Threshold (T
A
= 25_C)
Internal NFET ON−Resistance
Internal PFET ON−Resistance
LX Switch Current Limit (N−FET) (Note 7)
Operating Current into BAT
(V
BAT
= 1.8 V, V
FB
= 1.8 V, V
LX
= 1.8 V, V
OUT
= 3.3 V)
Operating Current into OUT (V
FB
= 1.4 V, V
OUT
= 3.3 V)
LX Switch MAX. ON−Time (V
FB
= 1.0 V, V
OUT
= 3.3 V, T
A
= 25_C)
LX Switch MIN. OFF−Time (V
FB
= 1.0 V, V
OUT
= 3.3 V, T
A
= 25_C)
FB Input Current
True−Cutoff Current into BAT
(LBI/EN = GND, V
OUT
= 0, V
IN
= 3.3 V, LX = 3.3 V)
BAT−to−LX Resistance (V
FB
= 1.4 V, V
OUT
= 3.3 V) (Note 7)
LBI/EN Input Current
LBO Low Output Voltage (V
LBI
= 0, I
SINK
= 1.0 mA)
Soft−Start Time (V
IN
= 2.5 V, V
OUT
= 5.0 V, C
REF
= 200 nF) (Note 6)
EN Pin Shutdown Threshold (T
A
= 25°C)
Thermal Shutdown Temperature (Note 7)
Thermal Shutdown Hysteresis (Note 7)
5. Loading capability increases with V
OUT.
6. Design guarantee, value depends on voltage at V
OUT.
7. Values are design guaranteed.
Symbol
V
IN
V
OUT
V
REF_NL
V
REF_NL
TC
VREF
I
REF
V
REF_LOAD
V
REF_LINE
V
FB
V
FB
V
LBI
V
LBI
R
DS(ON)_N
R
DS(ON)_P
I
LIM
I
QBAT
I
Q
t
ON
t
OFF
I
FB
I
BAT
R
BAT_LX
I
LBI
V
LBO_L
T
SS
V
SHDN
T
SHDN
T
SDHYS
Min
1.0
1.5
1.183
1.174
−
−
Typ
−
−
1.200
−
0.03
2.5
Max
5.0
5.0
1.217
1.220
−
−
Unit
V
V
V
V
mV/°C
mA
−
−
1.192
1.184
1.162
1.182
−
−
−
−
−
0.46
−
−
−
−
−
−
−
0.35
−
−
0.05
0.05
1.200
−
1.0
1.0
1.208
1.210
1.230
mV
mV/V
V
V
V
V
W
W
A
mA
mA
ms
ms
nA
nA
W
nA
V
ms
V
°C
°C
1.200
0.3
0.3
1.5
1.3
8.5
0.72
0.12
1.0
50
100
1.5
−
1.5
0.5
−
30
1.218
−
−
−
3
14
1.15
0.22
50
−
−
50
0.2
20
0.67
145
−
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4
NCP1421
TYPICAL OPERATING CHARACTERISTICS
1.220
REFERENCE VOLTAGE, V
REF
/V
REFERENCE VOLTAGE, V
REF
/V
V
OUT
= 3.3 V
L = 10
mH
C
IN
= 22
mF
C
OUT
= 22
mF
C
REF
= 1.0
mF
T
A
= 25_C
V
IN
= 1.5 V
V
IN
= 2.0 V
1.220
C
REF
= 200 nF
I
REF
= 0 mA
T
A
= 25°C
1.210
1.210
1.200
V
IN
= 2.5 V
1.200
1.190
1.190
1.180
1
10
100
1000
1.180
1.5
2
2.5
3
3.5
4
4.5
5
OUTPUT CURRENT, I
LOAD
/mA
VOLTAGE AT OUT PIN, V
OUT
/V
Figure 2. Reference Voltage vs. Output Current
SWITCH ON RESISTANCE, R
DS(ON)
/W
1.205
REFERENCE VOLTAGE, V
REF
/V
Figure 3. Reference Voltage vs. Voltage at OUT Pin
0.6
V
OUT
= 3.3 V
0.5
0.4
P−FET (M2)
0.3
0.2
0.1
0.0
−40
N−FET (M1)
1.200
1.195
1.190
V
OUT
= 3.3 V
C
REF
= 200 nF
I
REF
= 0 mA
−20
0
20
40
60
80
100
1.185
1.180
−40
−20
0
20
40
60
80
100
AMBIENT TEMPERATURE, T
A
/°C
AMBIENT TEMPERATURE, T
A
/°C
Figure 4. Reference Voltage vs. Temperature
L
X
SWITCH MAXIMUM, ON TIME, t
ON
/mS
1.0
MINIMUM STARTUP BATTERY
VOLTAGE, V
BATT
/V
1.6
Figure 5. Switch ON Resistance vs. Temperature
0.9
1.4
0.8
1.1
0.7
0.6
0.9
T
A
= 25°C
0.6
0
50
100
150
200
250
0.5
−40
−20
0
20
40
60
80
100
AMBIENT TEMPERATURE, T
A
/°C
OUTPUT LOADING CURRENT, I
LOAD
/mA
Figure 6. L
X
Switch Max. ON Time vs. Temperature
Figure 7. Minimum Startup Battery Voltage vs.
Loading Current
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