IR3651SPBF International Rectifier, IR3651SPBF Datasheet - Page 17

• Manufacturer Part Number: IR3651SPBF
• Description: IC CTLR SYNC PWM BUCK 14-SOIC
• Manufacturer: International Rectifier

Specifications of IR3651SPBF

• Pwm Type: Voltage Mode
• Number Of Outputs: 1
• Frequency - Max: 460kHz
• Duty Cycle: 80%
• Voltage - Supply: 4.5 V ~ 13.2 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: 0°C ~ 125°C
• Package / Case: 14-SOIC (3.9mm Width), 14-SOL
• Frequency-max: 460kHz
• Package: 14-Pin SOIC (NB)
• Circuit: Sync PWM Controller
• Vcc (min): 4.5
• Vcc (max): 13.2
• Iout (a): 25
• Switch Freq (khz): programmable to 400kHz
• Pbf: PbF Option Available
• For Use With: IRDC3651 - KIT REF DESIGN SYNCH BUCK REG
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Based on the frequency of the zero generated by
output capacitor and its ESR versus crossover
frequency, the compensation type can be
different.
compensation types and location of crossover
frequency.
Table1- The compensation type and location
The details of these compensation types are
discussed in application note AN-1043 which can
be downloaded from IR Web-Site.
For F
typeIII method B is selected to place the pole and
zeros.
12/07/2010
Compensator
type
TypeIII(PID)
TypeIII(PID)
Method A
Method B
TypII(PI)
F
F
Select
R
Z
P
F
LC
3
2
2
o
≥
=
=
<F
<
g
F
F
2
F
m
o
o
o
:
ESR
<F
*
*
;
The
F
of F
Z1
and
1
1
1
1
s/2
=
−
+
+
−
<F
ESR
0
Sin
Sin
Sin
Sin
F
F
F
F
.
5
LC
LC
LC
o
ESR
table
Θ
Θ
Θ
Θ
*
≤
versus F
F
<F
<F
<F
F
(
ESR
1/5
Z
2
ESR
o
o
<F
<F
and
~
vs. F
<F
ESR
s/2
1/10
below
<F
o
o
<F
<F
F
o
)
P3
ESR
*
s/2
s/2
F
=
s
0.5
shows
Output
capacitor
Electrolytic
*
, Tantalum
Tantalum,
Ceramic
ceramic
F
s
the
The following design rules will give a crossover
frequency
switching frequency. The higher the band width,
the potentially faster the load transient response.
The DC gain will be large enough to provide high
DC-regulation accuracy (typically -5dB to -12dB).
The phase margin should be greater than 45
overall stability.
Desired Phase Margin:
Calculate
C
C
C
Calculate
R
R
R
Programming the Current-Limit
The Current-Limit threshold can be set by
connecting a resistor (R
side MOSFET to the OCSet pin. The resistor
can be calculated by using equation (3).
The
coefficient and it should be considered for the
worse case operation. This resistor must be
placed close to the IC, place a small ceramic
capacitor from this pin to ground for noise
rejection purposes.
7
4
3
10
8
9
=
=
=
=
=
=
2
V
2
2
2
2
π
π
π
o
π
π
V
−
I
*
*
*
*
ref
R
SET
*
V
F
F
F
C
1
C
1
1
DS(on)
C
R
ref
o
Z1
P
1
7
R
7
approximately
3
=
4
*
10
*
*
*
,
*
*
3
L
,
I
C
F
R
R
L
R
R
F
o
*
(
Z
3
critical
V
P
8
*
2
3
3
8
2
;
and
in
C
;
;
and
−
;
o
has
)
R
*
=
10
C
V
R
;
R
7
osc
9
OCSet
:
:
;
R
a
IR3651SPBF
Θ
DS
∗
max
(
on
I
SET
OCSet
)
positive
one-tenth
=
) from drain of low
π
3
--(
) 3
temperature
of
o
the
for
17