IR3629AMTRPBF International Rectifier, IR3629AMTRPBF Datasheet - Page 11

• Manufacturer Part Number: IR3629AMTRPBF
• Description: IC CTLR PWM SYNC BUCK 12-MLPD
• Manufacturer: International Rectifier

Specifications of IR3629AMTRPBF

• Pwm Type: Voltage Mode
• Number Of Outputs: 1
• Frequency - Max: 330kHz
• Duty Cycle: 78%
• Voltage - Supply: 4.5 V ~ 14 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 12-MLPD
• Frequency-max: 330kHz
• Package: 12-Lead MLPD
• Circuit: Sync PWM Controller
• Vcc (min): 4.0
• Vcc (max): 30
• Switch Freq (khz): Internal 300kHz
• Pbf: PbF Option Available
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: IR3629AMTRPBFTR

Fig. 10: Typical application of the IR3629A for
Application Information
Design Example:
The following example is a typical application for
IR3629A. The application circuit is shown on
page 18.
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 0.6V. The divider is
ratioed to provide 0.6V 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 10.
Equation (4) can be rewritten as:
For the calculated values of R
feedback compensation section.
11/29/2007
R
V
V
I
F
ΔV
9
o
in
o
s
=
=
=
=
=
o
1
25
300
12
≤
R
.
8
V
programming the output voltage
V
8
V,(
A
IR3624
o
54
IR3629A
∗
kHz
=
⎛
⎜ ⎜
⎝
13
V
mV(output
V
ref
V
O
.
2
−
ref
V,
∗
V
⎛
⎜ ⎜
⎝
ref
max
1
Fb
⎞
⎟ ⎟
⎠
+
R
R
)
8
9
voltage ri
--(
⎞
⎟ ⎟
⎠
) 5
--(
) 4
V
8
pple)
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 10ms, the soft-start
capacitor will be 0.2uF. Choose a ceramic
capacitor at 0.22uF.
Vc supply for single input voltage
To drive the high side switch, it is necessary to
supply a gate voltage at least 4V greater than the
bus voltage. This is achieved by using a charge
pump configuration as shown in figure 11. This
method is simple and inexpensive. The operation
of the circuit is as follows: when the lower
MOSFET is turned on, the capacitor
pulled down to ground and charges, up to V
value, through the diode (D1). The bus voltage
will be added to this voltage when the upper
MOSFET turns on in the next cycle, and
providing supply voltage (Vc) through diode (D2).
Vc is approximately:
A capacitors in the range of 0.1uF is generally
adequate for most applications. Fast recovery
diodes must be used to minimize the amount of
charge fed back from the charge pump capacitor
into V
the full power rail voltage, which is seen when
the high-side MOSFET is switched on. For low-
voltage applications, schottky diodes can be
used to minimize forward drop.
IR3629/29A
Fig. 11: Charge pump circuit to generate
IR3624
BUS
IR3629/IR3629A MPbF
V
start
C
. The diodes need to be able to block
≅
is the desired start-up time (ms).
2
V
∗
C
BUS
V
SS
bus
≅
−
Vc voltage
20
(
V
D
μ
1
C3
Vc
HDrv
A
+
*
V
C2
T
D
start
2
)
D2
D1
C1
--(
--(
) 6
) 1
V
BUS
Q2
Q1
L
(C1) is
BUS
11