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NCP1423DMR2

P1-P3P4-P6P7-P9P10-P12P13-P14
NCP1423, SCV1423
http://onsemi.com
13
General Design Procedures
Switching mode converter design is important. Suitable
choice an inductor and capacitor value can make the
converter has an optimum performance. Below a simple
method base on the most basic first order equations to
estimate the inductor and capacitor values for NCP1423
operate in Continuous Conduction Mode (CCM) is
introduced. The component value set can be used as a
starting point to fine−tune the circuit operation. By all
means, detail bench testing is needed to get the best
performance out of the circuit.
Design Parameters:
For one cells supply application
V
IN
= 1.1 V to 1.5 V, Typical 1.3 V
V
OUT
= 3.3 V
I
OUT
= 150 mA (200 mA max)
V
LB
= 1.0 V
V
OUT−RIPPLE
= 30 mV
p−p
at I
OUT
= 150 mA
Calculate the feedback network:
Select R2 = 100 k
R1 + R2
ǒ
V
OUT
V
FB
* 1
Ǔ
R1 + 100 k
ǒ
3.3 V
0.5 V
* 1
Ǔ
+ 560 k
Calculate the Low Battery Detect divider:
V
LB0
= 1.0 V
Select R4 = 100 k
R3 + R4
ǒ
V
LB0
V
LB1
* 1
Ǔ
R3 + 100 k
ǒ
1.0 V
0.5 V
* 1
Ǔ
+ 100 k
Determine the steady state duty ratio, D for typical V
IN
,
operation will be optimized around this point:
V
OUT
V
IN
+
1
1 * D
D + 1 *
V
IN
V
OUT
+ 1 *
1.3 V
3.3 V
+ 0.606
Determine the average inductor current, I
LAVG
at
maximum I
OUT
:
I
LAVG
+
I
OUT
1 * D
+
150 mA
1 * 0.606
+ 381 mA
Assume the efficiency h = 85%
Determine the peak inductor ripple current, I
RIPPLE−P
and
calculate the inductor value:
Assume I
RIPPLE−P
is 40% of I
LAVG
, the inductance of the
power inductor can be calculated as in below:
I
RIPPLE−P
= 0.40 x 381 mA / h = 179 mA
L +
V
IN
t
ON
2I
RIPPLE*P
+
1.3 V 1.4 mS
2 (179 mA)
+ 5.0 mH
A standard value of 5.6 mH is selected for initial trial.
Determine the output voltage ripple, V
OUT−RIPPLE
and
calculate the output capacitor value:
V
OUT−RIPPLE
= 30 mV
P−P
at I
OUT
= 150 mA
C
OUT
u
I
OUT
t
ON
V
OUT*RIPPLE
* I
OUT
ESR
COUT
where t
ON
= 1.4 mS and ESR
COUT
= 0.1 W,
From above calculation, you need at least 14 mF in order
to achieve the specified ripple level at conditions stated.
Practically, a one level larger capacitor will be used to
accommodate factors not taken into account in the
calculations. Therefore, a capacitor value of 22 mF is
selected. The NCP1423 is internal compensated for most
applications. But in case additional compensation is
required, the capacitor C1 can be used as external
compensation adjustment to improve system dynamics.
Feedforward Capacitor (C1) Selection
A feedforward capacitor might be required to be added in
parallel to the upper feedback resistor to avoid double
pulsing or group pulsing at the switching node which causes
larger inductor ripple current and higher output voltage
ripple. With adequate feedforward capacitor, evenly
distributed single pulses at the switching node can be
achieved. For NCP1423, the lower the switching frequency
is, the larger the feedforward capacitor value should be. For
initial trial value, the following equation can be used, but
actual value may need fine tuning:
C
FF
[
1
2 p
F
SW
20
R
1
F
SW
is the switching frequency measured for nominal
load. If a feedforward capacitor is used, the equation
provides an initial starting value. Some trimming of the
feedback capacitor may be required depending on the
desired output value.
NCP1423, SCV1423
http://onsemi.com
14
PACKAGE DIMENSIONS
S
B
M
0.08 (0.003) A
S
T
DIM MIN MAX MIN MAX
INCHESMILLIMETERS
A 2.90 3.10 0.114 0.122
B 2.90 3.10 0.114 0.122
C 0.95 1.10 0.037 0.043
D 0.20 0.30 0.008 0.012
G 0.50 BSC 0.020 BSC
H 0.05 0.15 0.002 0.006
J 0.10 0.21 0.004 0.008
K 4.75 5.05 0.187 0.199
L 0.40 0.70 0.016 0.028
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSION “A” DOES NOT INCLUDE MOLD
FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE
BURRS SHALL NOT EXCEED 0.15 (0.006)
PER SIDE.
4. DIMENSION “B” DOES NOT INCLUDE
INTERLEAD FLASH OR PROTRUSION.
INTERLEAD FLASH OR PROTRUSION
SHALL NOT EXCEED 0.25 (0.010) PER SIDE.
5. 846B−01 OBSOLETE. NEW STANDARD
846B−02
−B−
−A−
D
K
G
PIN 1 ID
8 PL
0.038 (0.0015)
−T−
SEATING
PLANE
C
H
J
L
ǒ
mm
inches
Ǔ
SCALE 8:1
10X 10X
8X
1.04
0.041
0.32
0.0126
5.28
0.208
4.24
0.167
3.20
0.126
0.50
0.0196
Micro10
CASE 846B−03
ISSUE 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.
SOLDERING FOOTPRINT*
ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number of patents, trademarks,
copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. SCILLC
reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any
particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without
limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications
and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC
does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for
surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where
personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and
its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly,
any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture
of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
P
UBLICATION ORDERING INFORMATION
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Phone: 81−3−5817−1050
NCP1423/D
SENSEFET is a trademark of Semiconductor Components Industries, LLC.
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P1-P3P4-P6P7-P9P10-P12P13-P14

NCP1423DMR2

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Description:
IC REG BOOST ADJ 1.2A 10MICRO
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