ncp1529 ON Semiconductor, ncp1529 Datasheet - Page 12

• Manufacturer Part Number: ncp1529
• Description: High Efficiency Dc-dc Converters
• Manufacturer: ON Semiconductor

Output Voltage Selection
resistor divider connected from V
resistor from FB to GND (R2) should be in the [100k-600k]
range. If R2 is 200 k given the V
through the divider will be 3.0 mA.
desired R1 and the R1 value:
•
•
•
•
Input Capacitor Selection
with large switching noise. Using an input bypass capacitor
can reduce the peak current transients drawn from the input
supply
significantly. The capacitance needed for the input bypass
capacitor depends on the source impedance of the input
supply.
with maximum output current, which is IO, max/2.
should be used for most of the cases. For effective bypass
results, the input capacitor should be placed as close as
possible to the VIN Pin
Output L-C Filter Design Considerations
current mode architecture. The correct selection of the
output filter ensures good stability and fast transient
response.
filter must be selected to work with internal compensation.
For NCP1529, the internal compensation is internally fixed
and it is optimized for an output filter of L = 2.2 mH and
C
The corner frequency is given by:
V
Table 1. LIST OF INPUT CAPACITOR
OUT
Taiyo Yuden
The output voltage is programmed through an external
For low power consumption and noise immunity, the
The formula below gives the value of V
In PWM operating mode, the input current is pulsating
The maximum RMS current occurs at 50% duty cycle
For NCP1529, a low profile ceramic capacitor of 4.7 mF
The NCP1529 operates at 1.7 MHz frequency and uses
Due to the nature of the buck converter, the output L-C
V
V
R1: Feedback Resistor from V
R2: Feedback Resistor from FB to GND
out
f +
OUT
FB
Murata
TDK
+ V
= 10 mF.
: Feedback Voltage = 0.6 V
2p L
: Output Voltage (V)
source,
FB
1
(1 ) R1 R2)
C
GRM188R60J475KE
GRM21BR71C475KA
JMK212BY475MG
C2012X5R0J475KT
C1608X5R0J475KT
OUT
thereby
+
2p 2.2 mH
reducing
OUT
OUT
1
FB
to FB
is 0.6 V, the current
to FB then to GND.
10 mF
switching
OUT
APPLICATION INFORMATION
+ 34 kHz
, given the
4.7 mF
4.7 mF
4.7 mF
(eq. 2)
(eq. 3)
http://onsemi.com
noise
NCP1529
12
the corner frequency is moved, it is recommended to check
the loop stability depending of the accepted output ripple
voltage and the required output current. Take care to check
the loop stability. The phase margin is usually higher than
45°.
Inductor Selection
performances are saturation current and DC resistance and
inductance value. The inductor ripple current (DI
decreases with higher inductance:
•
•
•
higher than the maximum load current plus half the ripple
current:
•
•
efficiency of the converter. For best performances, the DC
resistance should be less than 0.3 W for good efficiency.
Output Capacitor Selection
desired output ripple voltage. Ceramic capacitors with low
ESR values will have the lowest output ripple voltage and
are strongly recommended. The output capacitor requires
either an X7R or X5R dielectric.
Table 2. L-C FILTER EXAMPLE
Table 3. LIST OF INDUCTOR
The device operates with inductance value of 2.2 mH. If
The inductor parameters directly related to device
The saturation current of the inductor should be rated
The inductor's resistance will factor into the overall
Selecting the proper output capacitor is based on the
The output ripple voltage in PWM mode is given by:
DI
L: Inductor value
f
I
I
SW
L(max)
O(max)
L
: Switching frequency
: Peak to peak inductor ripple current
Inductance (L)
: Maximum inductor current
Taiyo Yuden
: Maximum Output current
Coil Craft
2.2 mH
4.7 mH
FDK
TDK
DI
I
L(max)
L
+
L
+ I
V
OUT
O(max)
f
SW
)
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1 *
Output Capacitor (C
DI
2
V
L
V
OUT
IN
4.7 mF
10 mF
OUT
(eq. 4)
(eq. 5)
)
L
)