NCP1443FR4 ON Semiconductor, NCP1443FR4 Datasheet - Page 13

• Manufacturer Part Number: NCP1443FR4
• Description: IC REG 4A 280KHZ NEG POWERFLEX7
• Manufacturer: ON Semiconductor
• Type: Step-Up (Boost), Inverting, Flyback, Forward Converter, Sepicr

Specifications of NCP1443FR4

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: Adjustable
• Current - Output: 4A
• Frequency - Switching: 280kHz
• Voltage - Input: 2.7 ~ 30 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: Powerflex-7
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -
• Other names: NCP1443FR4OSTR

Magnetic Component Selection
factors such as peak current, core and ferrite material, output
voltage ripple, EMI, temperature range, physical size and
cost. In boost circuits, the average inductor current is the
product of output current and voltage gain (V
assuming 100% energy transfer efficiency. In continuous
conduction mode, inductor ripple current is:
where:
half of the ripple current, which should not cause inductor
saturation. The above equation can also be referenced when
selecting the value of the inductor based on the tolerance of
the ripple current in the circuits. Small ripple current
provides the benefits of small input capacitors and greater
output current capability. A core geometry like a rod or
barrel is prone to generating high magnetic field radiation,
but is relatively cheap and small. Other core geometries,
such as toroids, provide a closed magnetic loop to prevent
EMI.
Input Capacitor Selection
filter, as shown in Figure 34. In continuous mode, the input
current waveform is triangular and does not contain a large
pulsed current, as shown in Figure 33. This reduces the
requirements imposed on the input capacitor selection.
During continuous conduction mode, the peak to peak
inductor ripple current is given in the previous section. As
we can see from Figure 33, the product of the inductor
current ripple and the input capacitor’s effective series
resistance (ESR) determine the V
applications, input capacitors in the range of 10 mF to
100 mF with an ESR less than 0.3 W work well up to a full
4.0 A switch current.
When choosing a magnetic component, one must consider
The peak inductor current is equal to average current plus
In boost circuits, the inductor becomes part of the input
f = 280 kHz for NCP1442/3 and 560 kHz for NCP1444/5.
Figure 33. Boost Input Voltage and Current
I RIPPLE +
Ripple Waveforms
V CC (V OUT * V CC )
(f)(L)(V OUT)
CC
ripple. In most
OUT
V
I
I
IN
L
CC
http://onsemi.com
/V
ripple
CC
),
13
current is discontinuous and a significant pulsed current is
seen by the input capacitors. Therefore, there are two
requirements for capacitors in a flyback regulator: energy
storage and filtering. To maintain a stable voltage supply to
the chip, a storage capacitor larger than 20 mF with low ESR
is required. To reduce the noise generated by the inductor,
insert a 1.0 mF ceramic capacitor between V
as close as possible to the chip.
Output Capacitor Selection
see that the output voltage ripple comes from two major
sources,
charging/discharging of the output capacitor. In boost
circuits, when the power switch turns off, I
output capacitor causing an instant DV = I
same time, current I
increases the output voltage gradually. When the power
switch is turned on, I
discharges the output capacitor. When the I
enough, I
The situation is different in a flyback circuit. The input
By examining the waveforms shown in Figure 35, we can
Figure 35. Typical Output Voltage Ripple
V
Figure 34. Boost Circuit Effective Input Filter
CC
L
can be treated as a constant and is equal to input
namely
+
−
L
L
− I
capacitor
is shunted to ground and I
I
IN
OUT
R
charges the capacitor and
ESR
C
IN
ESR
IN
L
L
CC
ripple is small
flows into the
× ESR. At the
I
and ground
and
L
V
I
L
OUT
ripple
OUT
the