IR3895MPBF IRF [International Rectifier], IR3895MPBF Datasheet - Page 26

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

DESIGN EXAMPLE
The following example is a typical application for
IR3895. The application circuit is shown in Fig.28.
Enabling the IR3895
As explained earlier, the precise threshold of the
Enable lends itself well to implementation of a UVLO
for the Bus Voltage as shown in Fig. 22.
For a typical Enable threshold of V
For V
choice.
Programming the frequency
For F
Figure 22: Using Enable pin for UVLO implementation
V
R
s
in
in
= 600 kHz, select R
2
V
V
(min)
Ripple Voltage= 1%*
I
ΔV
F
(min)

o
in
o
s
= 16 A
=1 2 V
=600 kHz
=12 V ( 10% )
o
R
=9.2V, R
=
*
.
1
V
R
26

in(
1
6% *
R

min
2

V
R
1
EN
)
2
AUGUST 08, 2012 | DATA SHEET| Rev 3.1
=49.9K and R
V

o

V

V
for
EN
t
EN
= 39.2 KΩ, using Table 1.

50%

V
o
1.2
2

=7.5K ohm is a good
load transient
EN
= 1.2 V
Single‐Input Voltage, Synchronous Buck Regulator
(7)
(8)
)
- 26 -P
16A Highly Integrated SupIRBuck
Output Voltage Programming
Output voltage is programmed by reference voltage and
external voltage divider. The Fb pin is the inverting input
of the error amplifier, which is internally referenced to
0.5V. The divider ratio is set to provide 0.5V at the Fb pin
when the output is at its desired value. The output
voltage is defined by using the following equation:
When an external resistor divider is connected to the
output as shown in Fig. 23.
For the calculated values of R5 and R6, see feedback
compensation section.
Bootstrap Capacitor Selection
To drive the Control FET, it is necessary to supply a gate
voltage at least 4V greater than the voltage at the SW
pin, which is connected to the source of the Control FET.
This is achieved by using a bootstrap configuration,
which comprises the internal bootstrap diode and an
external bootstrap capacitor (C1). The operation of the
circuit is as follows: When the sync FET is turned on, the
capacitor node connected to SW is pulled down to
ground. The capacitor charges towards V
internal bootstrap diode (Fig.24), which has a forward
voltage drop V
capacitor C1 is approximately given as:
When the control FET turns on in the next cycle, the
capacitor node connected to SW rises to the bus voltage
Figure 23: Typical application of the IR3895
for programming the output voltage
R
V
6
o
D
V

. The voltage V

c
V
R

ref
5
V

cc








V

1
V
V
o

D

ref

V
R
R
c
ref
5
6
across the bootstrap









(11)
IR3895
(9)
(10)
cc
through the
PD‐97746