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PDF NCP1422 Data sheet ( Hoja de datos )
| Número de pieza | NCP1422 | |
| Descripción | Sync-Rect PFM Step-Up DC-DC Converter | |
| Fabricantes | ON Semiconductor | |
| Logotipo |  |
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NCP1422
800 mA Sync−Rect PFM
Step−Up DC−DC Converter
with True−Cutoff and
Ring−Killer
NCP1422 is a monolithic micropower high−frequency step−up
switching converter IC specially designed for battery−operated
hand−held electronic products up to 800 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 DFN−10 package.
Features
• 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 800 mA at VIN = 2.5 V and VOUT = 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% @ 25°C, can
Supply 2.5 mA Loading Current when VOUT > 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
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
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MARKING
DIAGRAM
DFN−10 1
1422
MN SUFFIX
CASE 485C
ALYWG
G
1
1422 = Device Code
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G = Pb−Free Package
(Note: Microdot may be in either location)
PIN CONNECTIONS
FB 1
LBI/EN 2
LBO 3
NC 4
REF 5
DFN−10
10 OUT
9 NC
8 LX
7 GND
6 BAT
(Top View)
ORDERING INFORMATION
Device
Package
Shipping†
NCP1422MNR2 DFN−10 3000 Tape & Reel
NCP1422MNR2G DFN−10 3000 Tape & Reel
(Pb−Free)
†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.
*For additional information on our Pb−Free strategy
and soldering details, please download the
ON Semiconductor Soldering and Mounting
Techniques Reference Manual, SOLDERRM/D.
© Semiconductor Components Industries, LLC, 2006
February, 2006 − Rev. 3
1
Publication Order Number:
NCP1422/D
1 page  
NCP1422
TYPICAL OPERATING CHARACTERISTICS
1.220
1.210
1.200
VOUT = 3.3 V
L = 10 mH
CIN = 22 mF
COUT = 22 mF
CREF = 1.0 mF
TA = 25_C
1.190
VIN = 1.5 V
VIN = 2.0 V
1.220
1.210
CREF = 200 nF
IREF = 0 mA
TA = 25°C
VIN = 2.5 V
1.200
1.190
1.180
1
10 100
OUTPUT CURRENT, ILOAD/mA
1000
Figure 2. Reference Voltage vs. Output Current
1.180
1.5 2 2.5 3 3.5 4 4.5 5
VOLTAGE AT OUT PIN, VOUT/V
Figure 3. Reference Voltage vs. Voltage at OUT Pin
1.205
1.200
0.6
VOUT = 3.3 V
0.5
1.195
1.190
1.185
1.180
−40
VOUT = 3.3 V
CREF = 200 nF
IREF = 0 mA
−20 0 20 40 60 80
AMBIENT TEMPERATURE, TA/°C
100
Figure 4. Reference Voltage vs. Temperature
0.4
P−FET (M2)
0.3
0.2 N−FET (M1)
0.1
0.0
−40 −20
0
20 40 60 80 100
AMBIENT TEMPERATURE, TA/°C
Figure 5. Switch ON Resistance vs. Temperature
1.0 1.6
0.9
0.8
0.7
0.6
0.5
−40
−20 0 20 40 60 80
AMBIENT TEMPERATURE, TA/°C
100
Figure 6. LX Switch Max. ON Time vs. Temperature
1.4
1.1
0.9
TA = 25°C
0.60 50 100 150 200 250
OUTPUT LOADING CURRENT, ILOAD/mA
Figure 7. Minimum Startup Battery Voltage vs.
Loading Current
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5
5 Page 
NCP1422
TYPICAL APPLICATION CIRCUIT
VIN
C1
22 mF
L
6.5 mH
Shutdown
Open Drain
Input
R2 200 k
Low Battery
Open Drain
Output
*Optional
C4 R3
10 p* 220 k
R4
330 k
R1
350 k
NCP1422
FB
LBI/EN
LBO
REF
C3
200 nF
OUT
LX
GND
BAT
C2 +
33 mF
VOUT = 3.3 V
800 mA
Figure 23. Typical Application Schematic for 2 Alkaline Cells Supply
GENERAL DESIGN PROCEDURES
Switching mode converter design is considered a
complicated process. Selecting the right inductor and
capacitor values can allow the converter to provide
optimum performance. The following is a simple method
based on the basic first−order equations to estimate the
inductor and capacitor values for NCP1422 to operate in
Continuous Conduction Mode (CCM). The set component
values can be used as a starting point to fine tune the
application circuit performance. Detailed bench testing is
still necessary to get the best performance out of the circuit.
Design Parameters:
VIN = 1.8 V to 3.0 V, Typical 2.4 V
VOUT = 3.3 V
IOUT = 500 mA
VLB = 2.0 V
VOUT−RIPPLE = 40 mVp−p at IOUT = 500 mA
Calculate the feedback network:
Select R2 = 200 k
ǒ ǓR1 + R2
VOUT
VREF
*
1
ǒ ǓR1 + 200 k
3.3 V
1.20 V
*
1
+ 350 k
Calculate the Low Battery Detect divider:
VLB = 2.0 V
Select R4 = 330 k
ǒ ǓR3 + R4
VLB
VREF
*
1
ǒ ǓR3 + 300 k
2.0 V
1.20 V
*
1
+ 220 k
Determine the Steady State Duty Ratio, D, for typical
VIN. The operation is optimized around this point:
VOUT
VIN
+
1
1
*
D
D
+
1
*
VIN
VOUT
+
1
*
2.4
3.3
V
V
+
0.273
Determine the average inductor current, ILAVG, at
maximum IOUT:
ILAVG
+
IOUT
1*D
+
500 mA
1 * 0.273
+
688
mA
Determine the peak inductor ripple current, IRIPPLE−P,
and calculate the inductor value:
Assume IRIPPLE−P is 20% of ILAVG. The inductance of the
power inductor can be calculated as follows:
L
+
2
VIN tON
IRIPPLE*P
+
2.4
2
V 0.75 mS
(137.6 mA)
+
6.5
mH
A standard value of 6.5 mH is selected for initial trial.
Determine the output voltage ripple, VOUT−RIPPLE, and
calculate the output capacitor value:
VOUT−RIPPLE = 40 mVP−P at IOUT = 500 mA
COUT
u
IOUT
VOUT*RIPPLE *
tON
IOUT
ESRCOUT
where tON = 0.75 mS and ESRCOUT = 0.05 ,
COUT
u
45
500 mA
mV * 500
0.75
mA
mS
0.05
W
+
18.75
mF
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11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet NCP1422.PDF ] | |
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