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參數(shù)資料
| 型號： | IR3651SPBF |
| 廠商： | International Rectifier |
| 英文描述： | HIGH VOLTAGE SYNCHRONOUS PWM BUCK CONTROLLER |
| 中文描述： | 高壓同步PWM降壓控制器 |
| 文件頁數(shù)： | 9/19頁 |
| 文件大?。?/td> | 397K |
| 代理商： | IR3651SPBF |
IR3651SP
b
F
10/11/2006
Circuit Description
9
THEORY OF OPERATION
Introduction
The
IR3651
synchronous controller. The output voltage is set
by feedback pin (Fb) and the internal reference
voltage (1.25V). These are two inputs to error
amplifier. The error signal between these two
inputs is compared to a fixed frequency linear
sawtooth ramp and generates fixed frequency
pulses of variable duty-cycle (D) which drivers N-
channel external MOSFETs.
The timing of the IC is controlled by an internal
oscillator
circuit
that
programmed up to 400kHz.
The IR3651 operates with a wide input voltage
from 36V to 75V allowing an extended operating
input voltage range.
The current limit is programmable and uses on-
resistance of the low-side MOSFET, eliminating
the need for an external current sense resistor
.
is
a
voltage
mode
PWM
can
be
externally
Under-Voltage Lockout
The under-voltage lockout circuit monitors the
Vcc supply and assures that the IC doesn’t starts
until the Vcc reaches the set threshold. Lockout
occurs if Vcc falls below 4.1V. Normal operation
resumes once Vcc rises above the set value.
Shutdown
The output can be shutdown by pulling the soft-
start pin below 0.3V. This can be easily done by
using an external small signal transistor. During
shutdown both MOSFET drivers will be turned
off. Normal operation will resume by cycling soft
start pin.
Error Amplifier
The IR3651 is a voltage mode controller. The
error amplifier is of transconductance type. The
amplifier is capable of operating with Type III
compensation control scheme using low ESR
output capacitance.
Operating Frequency Selection
The switching frequency is determined by
connecting an external resistor (Rt) to ground.
Figure 3 provides a graph of oscillator frequency
versus Rt.
Frequency Synchronization
The IR3651 is capable of accepting an external
digital synchronization signal. Synchronization
will be enabled by the rising edge at an external
clock. Switching frequency is set by external
resistor (Rt). During synchronization, Rt is
selected such that the free running frequency is
20% below the synchronization frequency.
When unused, the sync pin will remain floating
and is noise immune.
Pre-Bias Startup
IR3651 is able to start up into pre-charged
output,
which
prevents
disturbances of the output voltage.
The output starts in asynchronous fashion and
keeps the synchronous MOSFET off until the
first gate signal for control MOSFET is
generated. Below figure shows a typical Pre-
Bias condition at start up.
Depends on system configuration, specific
amount of output capacitors may be required to
prevent discharging the output voltage
oscillation
and
Fig. 3: Switching Frequency vs. Rt
Switching Frequency vs. Rt
0
50
100
150
200
250
300
350
400
450
0
50
100
150
200
250
300
Rt (Kohm)
S
Vo
Time
Volt
Pre-Bias Voltage
(Output Voltage before startup)
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| IR3651STRPBF | 功能描述:電壓模式 PWM 控制器 High Volt Sych PWM 100V 400Mhz 1.25 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(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 |
| IR3651STRPBF-CUT TAPE | 制造商:IR 功能描述:IR3651SPbF Series 13.2 V 7 mA High Voltage Synchronous PWM Buck Controller |
| IR367319 | 制造商:Thomas & Betts 功能描述:CONNECTOR |
| IR3702 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog IC |
| IR3702N | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog IC |
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