IR3623MPBF_1 IRF [International Rectifier], IR3623MPBF_1 Datasheet - Page 17

• Manufacturer Part Number: IR3623MPBF_1
• Description: HIGH FREQUENCY 2-PHASE, SINGLE OR DUAL OUTPUT SYNCHRONOUS STEP DOWN CONTROLLER WITH OUTPUT TRACKING AND SEQUENCING
• Manufacturer: IRF [International Rectifier]

V
V
I
F
Δ
Application Information
Design Example:
The following example is a typical application for
IR3623. The application circuit is shown in
page24.
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 0.8V. The divider is
ratioed to provide 0.8V 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 figure 17.
Equation (8) can be rewritten as:
For the calculated values of R
feedback compensation section.
o
Fig. 17: Typical application of the IR3623 for
www.irf.com
in
o
s
V
=
=
=
o
=
40
1
≤
600
12
.
8
30
A
V
programming the output voltage
V
V
R
kHz
( ,
o
mV
5
13
=
=
V
.
R
2
REF
V
6
IR3623
∗
,
∗
max)
⎛
⎜ ⎜
⎝
⎛
⎜ ⎜
⎝
V
1
V
o
+
−
ref
V
R
R
Fb1
ref
6
5
⎞
⎟ ⎟
⎠
⎞
⎟ ⎟
⎠
-
-
- -
- -
( -
( -
5
) 8
) 9
V
and R
OUT
R
R
5
6
6
see
I
Soft-Start Programming
The soft-start timing can be programmed by
selecting the soft-start capacitance value. The
start-up time of the converter can be calculated
by using:
Where T
For a start-up time of 5ms, the soft-start
capacitor will be 0.1uF. Choose a ceramic
capacitor at 0.1uF.
Input Capacitor Selection
The 180
of the ripple current seen by input capacitors.
This reduces numbers of input capacitors. The
input capacitors must be selected that can
handle both the maximum ripple RMS at highest
ambient temperature as well as the maximum
input voltage. The RMS value of current ripple for
duty cycle under 50% is expressed by:
Where:
-I
current
-D
-I
For Io=40A and D=0.13, the I
Ceramic capacitors are recommended due to
their peak current capabilities, they also feature
low ESR and ESL at higher frequency which
enhance better efficiency,
Use 15x22uF, 16V ceramic capacitor from TDK
(C3225X5R1C226M).
For the single output application when the duty
cycle is larger than 50% the following equation
can be used to calculate the total RMS value
input capacitor current:
RMS
RMS
1
1
and I
=
and D
I
RMS
is the RMS value of the input capacitor
(
I
1
2
2
o
=
D
start
are the output current for each channel
1
out of phase will reduce the RMS value
2
I
(
O
1
are the duty cycle for each channel
C
is the desired start-up time (ms)
−
(
2
SS
D
D
1
≅
)
(
1
+
20
−
I
2
2
D
D
μ
A
2
) (
(
+
1
*
T
−
2
IR3623MPbF
start
D
−
2
2
)
RMS
−
D
2
)
-
)
I I
- -
1
= 17.8A.
2
D
( -
1
10
D
D
2
>
)
)
0.5
-
- -
( -
11
17
)