参数资料
| 型号： | MAX5944ESE+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 10/15页 |
| 文件大小： | 0K |
| 描述： | IC FW CURR LIMITER DUAL 16-SOIC |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | FireWire? 应用程序 |
| FET 型： | N 沟道 |
| 输出数： | 2 |
| 内部开关： | 无 |
| 延迟时间 - 关闭： | 100ns |
| 电源电压： | 7.5 V ~ 37 V |
| 电流 - 电源： | 1.3mA |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 16-SOIC N |
| 包装： | 带卷 (TR) |
Dual FireWire Current Limiter and Low-Drop
ORing Switch Controller
Detailed Description
The MAX5944 dual-channel controller IC performs hot-
swapping, power-supply ORing, and current limiting for
FireWire power-supply applications. The MAX5944
incorporates four MOSFET drivers (GATE1_ and
GATE2_) to control external n-channel power MOSFETs
to perform low-voltage-drop power-supply ORing
(GATE1_), hot-swapping, and current limiting (GATE2_)
from the input power supply to the load. A sense resis-
tor provides accurate current limiting. GATE1_ and
GATE2_ provide true load disconnect to prevent current
flowing from either direction between IN_ and OUT_.
The MAX5944 independent channels remain in low-cur-
rent shutdown mode when V ON_ is below the 0.4V
threshold. Low-current shutdown mode disables the
MAX5944 channels resulting in less than 10μA supply
current per channel. Shutdown places all logic inputs in
a high-impedance state, which allows the inputs to be
connected to IN_ without drawing additional current
from the supply.
When either input supply voltage (V IN_ ) is above 7.5V
and V ON_ is above the V ON_REF threshold, the
MAX5944 channel turns on, sourcing 50μA current from
GATE2_ (current regulation), to enhance Q2_ slowly. If
the voltage across the current-sense resistor, V IS , is
greater than the current-limit threshold, the MAX5944
regulates the GATE2_ voltage to limit the load current at
the current-limit level so that V IS is equal to V TH . In nor-
mal operation, V IS drops below V TH and GATE2_ rises
to approximately 5.5V above OUT.
GATE1_ controls the MAX5944 ORing function. Initially,
GATE1_ is off (ONQ1 = low) and the load current con-
ducts through the body diode of Q1_. GATE1_ rises to
5.5V above IN_ when V IS exceeds V OR , thereby
enhancing Q1_ and reducing the voltage drop, power
dissipation, and heat generation in the power-supply
pathway. When a voltage greater than V IN_ is connect-
ed at OUT_, the higher voltage source commences pro-
viding current to the load. The MAX5944 turns off
GATE1_ rapidly upon V IS falling below the V OR hystere-
sis, thus blocking the higher voltage from backdriving
V IN_ . GATE1_ also turns off when the load current
drops, causing V IS to fall below V OR_ hysteresis.
Current Limiting
The MAX5944 limits the load current by monitoring the
voltage across R SENSE_ at all times and regulating the
current to the load as necessary to keep V IS to its cur-
rent-limit threshold voltage (V TH ). Set the maximum cur-
rent limit (I LIMIT ) by placing the appropriate sense
resistor between IN_ and SENSE_, where I LIMIT_ = V TH /
R SENSE_ . When the load current is less than I LIMIT ,
GATE2_ rises to V G2 (5.5V) to fully enhance MOSFET
Q2_ (see the Typical Operating Circuit ).
When the load attempts to draw more current than
I LIMIT , the MAX5944’s GATE2_ pulldown current (I G2D )
regulates the current through Q2_, causing OUT_ to act
as a constant current source. The output current is limit-
ed to I LIMIT . If the current-limit condition persists after
the 2ms current-limit timeout period (t ILIM ) has expired,
the GATE2_ strong pulldown current (I G2_OFF ) quickly
turns off GATE2_ to disconnect the load from the power
supply and FAULT_ asserts low (Figure 2a). If the cur-
rent-limit duration is less than t ILIM , GATE2_ pulls to
V GS2 (Figure 2b). During an output short circuit or a
gross overload, the load current overshoots and causes
V IS to exceed the fast pulldown current-limit threshold
voltage (V THF ). The MAX5944 responds with much
stronger GATE2_ pulldown currents (I G2DP and/or
I G2DF ) to quickly bring the load current back down to
the programmed current limit.
Current-Limit Threshold
The MAX5944 current limit has internal 50mV trip
threshold voltages (V TH ). Use the following formula to
calculate the maximum current:
I LIMIT = V TH / R SENSE_
where V TH is the 50mV (typ) threshold voltage across
R SENSE_ , and R SENSE_ is the sense resistor connected
between IN_ and SENSE_.
Power-Supply ORing, GATE1_
GATE1_ controls the MAX5944 ORing function. The
MAX5944 accomplishes a very low voltage-drop diode
ORing function using n-channel power MOSFETs.
Initially, GATE1_ is off (ONQ1 = low) and the load cur-
rent conducts through the body diode of Q1_, Figure 3.
GATE1_ rises to 5.5V above SENSE_ when V IS exceeds
the 5mV V OR threshold, enhancing Q1_. Q1_ ’s low
R DS(ON) provides a very low voltage drop across its
source to drain, which results in less power dissipation
and heat generation in the power-supply path than a
traditional diode.
The MAX5944 continuously monitors the load currents
through the voltage drops, V IS , across the current-sens-
ing resistors. Q1_ turns off rapidly when V IS decreases
below the V OR minus its hysteresis.
Connect ONQ1 to GND for a normal ORing function.
Drive ONQ1 high to force Q1 on, regardless of the
load-current condition, as long as voltages at IN_ and
ON_ exceed V UVLO and V ON-REF , repectively, and the
device is not in a current-fault shutdown.
10
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参数描述 |
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| MAX5944EVKIT | 功能描述:DC/DC 开关控制器 Evaluation Kit for the MAX5944 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 |
| MAX5945CAX | 功能描述:热插拔功率分布 RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| MAX5945CAX+ | 功能描述:热插拔功率分布 IEEE 802.3af Quad Net Pwr Controller RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| MAX5945CAX+T | 功能描述:热插拔功率分布 IEEE 802.3af Quad Net Pwr Controller RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| MAX5945CAX-T | 功能描述:热插拔功率分布 RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
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