IR3651SPBF International Rectifier, IR3651SPBF Datasheet - Page 12

• 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

Application Information
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 1.25V. The divider is
ratioed to provide 1.25V 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 9.
Equation (4) can be rewritten as:
For the calculated values of R
feedback compensation section.
12/07/2010
Fig. 9: Typical application of the IR3651 for
R
programming the output voltage
V
9
IR3651
o
=
=
R
V
8
ref
∗
∗
⎛
⎜ ⎜
⎝
V
⎛
⎜ ⎜
⎝
1
Fb
V
O
+
−
ref
V
R
R
ref
8
9
⎞
⎟ ⎟
⎠
⎞
⎟ ⎟
⎠
--(
--(
) 5
) 4
V
8
OUT
R
R
and R
9
8
9
see
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.
start
is the desired start-up time (ms)
C
SS
≅
20
μ
A
*
IR3651SPBF
T
start
--(
) 1
12