IR3895MPBF IRF [International Rectifier], IR3895MPBF Datasheet - Page 27

• Manufacturer Part Number: IR3895MPBF
• Description: 16A HIGHLY INTERGRATED SUPLRBUCK
• Manufacturer: IRF [International Rectifier]

V
the voltage V
unchanged and the voltage at the Boot pin becomes:
A bootstrap capacitor of value 0.1uF is suitable for
most applications.
Input Capacitor Selection
The ripple current generated during the on time of the
control FET should be provided by the input capacitor.
The RMS value of this ripple is expressed by:
Where:
in
. However, if the value of C1 is appropriately chosen,
D is the Duty Cycle
I
Io is the output current.
For I
I
D
RMS
Figure 24: Bootstrap circuit to generate Vc voltage
RMS

is the RMS value of the input capacitor current.
o
=16A and D = 0.1, the I
V
V

V
in
o
I
Boot

27
o
c
across C1 remains approximately


V
D
AUGUST 08, 2012 | DATA SHEET| Rev 3.1
in
 

(1
V
cc
D

V
)

D
RMS

= 4.8A.
Single‐Input Voltage, Synchronous Buck Regulator
(14)
(13)
(12)
- 27 -P
16A Highly Integrated SupIRBuck
Ceramic capacitors are recommended due to their peak
current capabilities. They also feature low ESR and ESL at
higher frequency which enables better efficiency.
For this application, it is advisable to have 5x10uF, 25V
ceramic capacitors, C3216X5R1E106M from TDK.
In addition to these, although not mandatory,
a 1x330uF, 25V SMD capacitor EEV‐FK1E331P from
Panasonic may also be used as a bulk capacitor and is
recommended if the input power supply is not located
close to the converter.
Inductor Selection
The inductor is selected based on output power,
operating frequency and efficiency requirements. A low
inductor value causes large ripple current, resulting in
the smaller size, faster response to a load transient but
poor efficiency and high output noise. Generally, the
selection of the inductor value can be reduced to the
desired maximum ripple current in the inductor (Δi). The
optimum point is usually found between 20% and 50%
ripple of the output current.
For the buck converter, the inductor value for the desired
operating ripple current can be determined using the
following relation:
Where:
If Δi ≈ 30%*I
be 0.38μH. Select L=0.4μH, 59PR9875N, from VITEC
which provides a compact, low profile inductor suitable
for this application.
V
V
Δi = Inductor Peak‐to‐Peak Ripple Current
F
Δt = On time for Control FET
D = Duty Cycle
s
V
in
0
= Switching Frequency
= Output Voltage
= Maximum input voltage
in
L


V
o

o
V
, then the output inductor is calculated to
 
in
L

V


o

t
i

;
V
in
 
 
t
V
o
i F
D
*

s
F
1
s

IR3895
PD‐97746
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