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參數(shù)資料
| 型號(hào)： | IRU3138 |
| 廠商： | International Rectifier |
| 英文描述： | SYNCHRONOUS PWM CONTROLLER FOR TERMINATION POWER SUPPLY APPLICATIONS |
| 中文描述： | 同步PWM控制器終止電源應(yīng)用 |
| 文件頁(yè)數(shù)： | 7/18頁(yè) |
| 文件大?。?/td> | 281K |
| 代理商： | IRU3138 |
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IRU3138
7
Rev. 1.0
01/29/04
www.irf.com
APPLICATION INFORMATION
Design Example:
The following example is a typical application for IRU3138,
the schematic is Figure 13 on page 15.
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 referenced to the voltage
on non-inverting pin of error amplifier. The output voltage
is defined by using the following equation:
R
6
R
5
( )
When an external resistor divider is connected to the
output as shown in Figure 5.
Figure 5 - Typical application of the IRU3138 for
programming the output voltage.
Equation (7) can be rewritten as:
( )
Choose R
5
= 1K
This will result to
R
6
= 1K
If the high value feedback resistors are used, the input
bias current of the Fb pin could cause a slight increase
in output voltage. The output voltage set point can be
more accurate by using precision resistor.
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
START
is the desired start-up time (ms)
For a start-up time of 5ms, the soft-start capacitor will
be 0.1
μ
F. Choose a ceramic capacitor at 0.1
μ
F.
Boost Supply Vc
To drive the high side switch, it is necessary to supply a
gate voltage at least 4V grater than the bus voltage. For
single supply applications, this is achieved by using a
charge pump configuration as shown in Figure 6. This
method is simple and inexpensive. The operation of the
circuit is as follows: when the lower MOSFET is turned
on, the capacitor (C1) is pulled down to ground and
charges, up to V
BUS
value, through the diode (D1). The
bus voltage will be added to this voltage when upper
MOSFET turns on in next cycle, and providing supply
voltage (Vc) through diode (D2). Vc is approximately:
Capacitors in the range of 0.1
μ
F and 1
μ
F are generally
adequate for most applications. The diode must be a
fast recovery device to minimize the amount of charge
fed back from the charge pump capacitor into Vc. The
diodes need to be able to block the full power rail volt-
age, which is seen when the high side MOSFET is
switched on. For low voltage application, schottky di-
odes can be used to minimize forward drop across the
diodes at start up. For this application, Vc is biased by
an external 12V supply.
Figure 6 - Charge pump circuit.
Input Capacitor Selection
The input filter capacitor should be based on how much
ripple the supply can tolerate on the DC input line. The
ripple current generated during the on time of upper
MOSFET should be provided by input capacitor. The RMS
value of this ripple is expressed by:
V
C
2
×
V
BUS
- (V
D1
+ V
D2
)
Css = 20
×
t
START
(
μ
F) ---(8)
V
IN
= V
CC
= 5V
V
OUT
= 1.6V
I
OUT
= 12A
V
OUT
= 50mV
(output voltage ripple
3% of V
OUT
)
f
S
= 400KHz
Supply Voltage
V
C
= 12V
L2
IRU3138
C1
Vc
HDrv
Q1
Q2
C2
V
BUS
D2
D1
R
6
= R
5
×
- 1
V
OUT
P
V
OUT
= V
P
×
1 +
---(7)
V
P
= V
REF
= 0.8V
Fb
IRU3138
V
P
V
OUT
R
5
R
6
V
REF
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| IRU3138CS | 制造商:IRF 制造商全稱:International Rectifier 功能描述:SYNCHRONOUS PWM CONTROLLER FOR TERMINATION POWER SUPPLY APPLICATIONS |
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| IRU3138CSTRPBF | 功能描述:電壓模式 PWM 控制器 SYNC PWM CTRLLER 1A .8V 200 to 400kHz RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
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