参数资料
| 型号： | MAX5944ESE+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 13/15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
MOSFET Selection
V IN
IN_
Select external MOSFETs according to the application
current level. The MOSFETs’ on-resistance (R DS(ON) )
should be chosen low enough to have minimum voltage
R1
R2
ON_
GND
MAX5944
drop at full load to limit the MOSFET power dissipation.
High R DS(ON) also causes large output ripple if there is
a pulsating load. Determine the device power rating to
accommodate a short-circuit condition on the board, at
startup, and when the device is in autoretry mode.
During normal operation, the external MOSFETs dissipate
little power. The power dissipated in normal operation is:
P = I LOAD2 x R DS(ON)
The most power dissipation will occur during a short-
Figure 7. Setting the MAX5944 Turn-On Voltage
to 1/129 under continuous fault conditions. FAULT_
deasserts every time a restart attempt is made.
Applications Information
Startup Considerations
Set the appropriate current-limit threshold for a suc-
cessful MAX5944 startup. A successful startup is
dependent on the MAX5944 current-limit threshold and
timeout period. A large capacitor at OUT will result in a
charging current equivalent to the current-limit thresh-
old and may cause the MAX5944 to exceed its 2ms
timeout period, if the current-limit threshold is set too
low. Use the following formula to compute the minimum
current-limit setting:
circuit event, resulting in high power dissipated in Q2
(Figure 8) during the timeout period for the MAX5944,
where the power dissipated across Q2 is:
P Q2 = (V IN - V IS - V Q1 ) x I LIMIT
Transient Protection
If IN_ or OUT_ experiences a fast transient rise in volt-
age, the drain-to-gate overlap capacitance of GATE1_
and/or GATE2_ FETs may be sufficient to enhance one
of the transistors, allowing current to flow. If the circuit is
subjected to large transients, connect capacitors from
the gate to source across the appropriate MOSFET to
prevent the overlap capacitance from turning on the
device. This results in the turn-off time of the FETs to
increase due to the additional discharge of the capaci-
tor. Use the minimum capacitor value that will prevent
reverse currents from flowing in hot-plug situations.
I LIMIT >
C OUT × V IN
t ILIM
+ I LOAD
FireWire Power Management
The MAX5944 serves to regulate and protect FireWire
power over a system interface. The MAX5944 program-
where I LIMIT is the programmed current limit, C OUT is
the capacitor at OUT, V IN is the supply voltage, t ILIM is
the 2ms current-limit timeout period, and I LOAD is the
load current during startup. With V IN = 12V, C OUT =
220μF, and I LOAD = 0, set the MAX5944 current limit
greater than 1.3A. This calculation does not include tol-
mable features that make it suitable for both power-
provider and power-receiver applications. Figure 9
shows a high-end two-port FireWire power-manage-
ment system using two MAX5944 dual-channel FireWire
current-limiting ICs.
erances.
Choosing RSENSE
V IN
+
V IS
-
+ V Q1 -
+ V Q2 -
I LIMIT
Select a sense resistor that causes the current-limit
voltage drop at a current-limit level above the maximum
Q1
Q2
normal operating current. Typically, set the current limit
IN_
SENSE_ GATE1_
GATE2_ OUT_
at 1.2 to 1.5 times the nominal load current.
Choose the sense-resistor power rating to accommo-
date a current-limit condition:
P SENSE = (V TH ) 2 / R SENSE
where P SENSE is the power dissipated across R SENSE
during a current-limit fault.
MAX5944
Figure 8. Power Dissipated Across MOSFET Q2 During a
Short-Circuit Fault
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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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