参数资料
型号: IR3640MPBF
厂商: International Rectifier
文件页数: 15/32页
文件大小: 0K
描述: IC REG CTRLR BUCK PWM VM 20-MLPQ
标准包装: 100
PWM 型: 电压模式
输出数: 1
频率 - 最大: 1.65MHz
占空比: 92%
电源电压: 4.5 V ~ 5.5 V
降压:
升压:
回扫:
反相:
倍增器:
除法器:
Cuk:
隔离:
工作温度: -40°C ~ 125°C
封装/外壳: 20-VFQFN 裸露焊盘
包装: 管件
IR3640MPBF
V o = V ref ? ? ? 1 + 8 ? ?
Application Information
Design Example:
The following example is a typical application for
IR3640. The application circuit is shown on page
23.
V in = 12 V,( 13 . 2 V, max )
V o = 1 . 8 V
I o = 25 A
Δ V o ≤ 54 mV
F s = 600 kHz
Enabling the IR3640
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 0.7V. The divider is
ratioed to provide 0.7V at the Fb pin when the
output is at its desired value. The output voltage
is defined by using the following equation:
? R ?
- -(7)
? R 9 ?
When an external resistor divider is connected to
the output as shown in figure 11.
As explained earlier, the precise threshold of
the Enable lends itself well to implementation of
a UVLO for the Bus Voltage.
V in
IR3640
R 1
Enable
IR3640
IR3624
Fb
V OU T
R 8
R 9
= V EN = 1.2
V in (min) *
R 2
R 9 = R 8 ? ?
? V ref ?
? V ? V
?
R 2
Fig. 12: Typical application of the IR3640 for
programming the Enable threshold
For a typical Enable threshold of V EN = 1.2 V
- -(5)
R 1 + R 2
Fig. 13: Typical application of the IR3640 for
programming the output voltage
Equation (7) can be rewritten as:
? - -(8)
? O ref ?
For the calculated values of R 8 and R 9 see
feedback compensation section.
R 2 = R 1
V EN
V in( min ) ? V EN
- -(6)
Soft-Start Programming
The soft-start timing can be programmed by
For a V in (min) =10.1V, R 1 =4.99K and R 2 =681 ohm
is a good choice.
selecting the soft-start capacitance value. The
start-up time of the converter can be calculated
by using:
Programming the frequency
C SS =
Tstart * 20uA
( 1.4 ? 0.7 ) V
- -(9)
For F s = 600 kHz, select R t = 23.7 k ? , using
Table. 1.
06/15/2009
Where T start is the desired start-up time (ms).
For a start-up time of 3.5ms, the soft-start
capacitor will be 0.099uF. Choose a ceramic
capacitor at 0.1uF.
15
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