NCP1417(2002) Ver la hoja de datos (PDF) - ON Semiconductor
Número de pieza
componentes Descripción
Fabricante
NCP1417 Datasheet PDF : 16 Pages
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NCP1417
kept away from the feedback (FB, pin 1) terminal to avoid
unwanted injection of noise into the feedback path.
Feedback Network
Feedback of the output voltage must be a separate trace
detached from the power path. External feedback network
must be placed very close to the feedback (FB, pin 1) pin and
sensing the output voltage directly at the anode of the output
capacitor.
TYPICAL APPLICATION CIRCUIT
Input
1 V to
VOUT
CIN
10 µF
CFR1
RFB2 150 pF
RFB1
355 K
NCP1417
200 K
1
8
308 K
FB
OUT
2
7
RLB1
3
LBI/SHDN LX
6
RLB2 4
LB01
REF
GND
LB02
5
Shutdown
330 K
Open Drain
Input
56 nF
150 nF
Low Battery
CSHDN
CREF
Open Drain
Output 1
L
22 µH
33 µF +
COUT
VOUT = 3.3 V/200 mA max.
Low Battery
Open Drain
Output 2
Figure 28. Typical Application Schematic for 2 Alkaline Cells Supply
GENERAL DESIGN PROCEDURES
Switch mode converter design is considered as black
magic to most engineers, some complicate empirical
formulae are available for reference usage. Those formulae
are derived from the assumption that the key components,
i.e. power inductor and capacitors are available with no
tolerance. Practically, its not true, the result is not a matter
of how accurate the equations you are using to calculate the
component values, the outcome is still somehow away from
the optimum point. Following, is a simple method based on
the most basic first order equations to estimate the inductor
and capacitor values for NCP1417 operating in Continuous
Conduction Mode. 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:
VIN = 1.8 V to 3.0 V, Typical 2.4 V
VOUT = 3.3 V
IOUT = 150 mA (200 mA max)
VLB1 = 2.3 V; VLB2 [ 0.8 VLB1 = 1.84 V
VOUT–RIPPLE = 40 mVP–P at IOUT = 200 mA
Calculate the feedback network:
Select RFB2 = 200 K
ǒ Ǔ RFB1 + RFB2
VOUT
VREF
*
1
ǒ Ǔ RFB1 + 200 K
3.3 V
1.19 V
*
1
+ 355 K
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