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| 型号： | IR3621FTR |
| 厂商： | International Rectifier |
| 文件页数： | 9/29页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 28TSSOP |
| 产品变化通告： | (EP) Parts Discontinuation 25/May/2012 |
| 标准包装： | 0 |
| PWM 型： | 电压模式 |
| 输出数： | 2 |
| 频率 - 最大： | 345kHz |
| 占空比： | 86.5% |
| 电源电压： | 5.5 V ~ 14.5 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 28-TSSOP（0.173"，4.40mm 宽） |
| 包装： | 标准包装 |
| 产品目录页面： | 1383 (CN2011-ZH PDF) |
| 配用： | IRDC3621-ND - BOARD EVAL DUAL SYNC BUCK CTRLR |
| 其它名称： | IR3621FDKR |
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IR3621 & (PbF)
For a given start up time, the soft-start capacitor can be
The internal current source develops a voltage across
calculated by:
C SS ? 28 μ A × T START /0.8V
R SET . When the low side switch is turned on, the induc-
tor current flows through the Q2 and results a voltage
The soft-start is part of the Over Current Protection
which is given by:
scheme, during the overload or short circuit condition
the external soft start capacitors will be charged and
discharged in certain slope rate to achieve the hiccup
V OCSET = I OCSET × R SET -R DS(ON) × i L
---(2)
mode function.
28uA
I OCSET
Hiccup
IR3621
Q1
OCSet R SET
L1
V OUT
SS1 / SD
20
3uA
Hiccup
Control
Q2
Figure 9 - Diagram of the over current sensing.
Figure 8 - 3uA current source for discharging soft
start-capacitor during Hiccup mode
The critical inductor current can be calculated by set-
Out-of-Phase Operation
The IR3621 drives its two output stages 180 out-of-phase.
ting:
V OCSET = I OCSET × R SET - R DS(ON) × I L = 0
In 2-phase configuration, the two inductor ripple currents
cancel each other and result in a reduction of the output
current ripple and yield a smaller output capacitor for the
I SET = I L(CRITICAL) =
R SET × I OCSET
R DS(ON)
---(3)
same ripple voltage requirement.
In single input voltage applications, the input ripple current The value of R SET should be checked in an actual
reduces. This results in much smaller input capacitor's circuit to ensure that the Over Current Protection
RMS current and reduces the input capacitor quantity.
Over-Current Protection
The IR3621 can provide two different schemes for Over-
Current Protection (OCP). When the Hiccup pin is pulled
high, the OCP will operate in hiccup mode. In this mode,
during overload or short circuit, the outputs enter hiccup
mode and stay in that mode until the overload or short
circuit is removed. The converter will automatically re-
cover.
When the Hiccup pin is pulled low, the OCP scheme
will be changed to the latch up type, in this mode the
converter will be turned off during Overcurrent or short
circuit. The power needs to be recycled for normal
operation.
Each phase has its own independent OCP circuitry.
The OCP is performed by sensing current through the
R DS(ON) of low side MOSFET. As shown in Figure 9, an
external resistor (R SET ) is connected between OCSet pin
and the drain of low side MOSFET (Q2) which sets the
current limit set point.
If using one soft start capacitor in dual configuration for a
precise power up the OCP needs to be set to latch mode.
circuit activates as expected. The IR3621 current limit
is designed primarily as disaster preventing, "no blow
up" circuit, and is not useful as a precision current
regulator.
In two independent mode, the output of each channel
is protected independently which means if one output
is under overload or short circuit condition, the other
output will remain functional. The OCP set limit can be
programmed to different levels by using the external
resistors. This is valid for both hiccup mode and latch
up mode.
In 2-phase configuration, the OCP's output depends on
any one channel, which means as soon as one
channel goes to overload or short circuit condition the
output will enter either hiccup or latch-up, dependes on
status of Hiccup pin.
Pre-bias Startup
The IR3621 allows pre-bias startup without discharging
the output capacitors. The output starts in asynchro-
nous fashion and keeps the synchronous MOSFET off
until the first gate signal for control MOSFET is gener-
ated.
www.irf.com
9
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| IR3621FTRPBF | 功能描述:DC/DC 开关控制器 2-PHASE DUAL SYNC PWM CTRLLER RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
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