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参数资料
| 型号： | LM3543MX-L/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 电源管理 |
| 英文描述： | 3-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO16 |
| 封装： | SOIC-16 |
| 文件页数： | 13/14页 |
| 文件大小： | 396K |
| 代理商： | LM3543MX-L/NOPB |
Functional Descriptions
POWER SWITCHES
The power switches that comprise the three ports of the
LM3543 are N-Channel MOSFETs. They have a typical on-
state drain-to-source resistance of 90 m
when the input
voltage is 5 V. When enabled, each switch will supply a 500
mA minimum current to its load. In the unlikely event that a
switch is enabled and the output voltage of that switch is
pulled above the input voltage, the bi-directional nature of the
switch results in current to flow from the output to the input.
When a switch is disabled, current flow through the switch is
prevented in both directions.
CHARGE PUMP AND DRIVER
The gate voltages of the high-side NFET power switches are
supplied by an internal charge-pump and driver circuit com-
bination. The charge pump is a low-current switched-capaci-
tor circuit that efficiently generates voltages above the
LM3543 input supply. The charge pump output is used to
supply a transconductance amplifier driver circuit that con-
trols the gate voltages of the power switches. Rise and fall
times on the gates are typically kept between 2 ms and 4 ms
to limit large current surges and associated electromagnetic
interference (EMI).
ENABLE (EN
x or ENx)
The LM3543 comes in two versions: an active-high enable
version, LM3543-H, and an active-low enable version,
LM3543-L. In the LM3543-H, the EN
x pins are active-high
logic inputs that, when asserted, turn on the associated power
supply switch(es). Power supply switches are controlled by
the EN
x active-low logic inputs in the LM3543-L. With all three
ports disabled on either version of the LM3543, less than 5
A of supply current is consumed. Both types of enable in-
puts, active-high and active-low, are TTL and CMOS logic
compatible.
INPUT AND OUTPUT
The power supply to the control circuitry and the drains of the
power-switch MOSFETs are connected to the two input pins,
IN1 and IN2. These two pins are connected externally in most
standard applications. The two ground nodes GND1 and
GND2 must be connected externally in all applications.
Pins OUT1, OUT2, and OUT3 are connections to the source
nodes of the power-switch MOSFETs. In a typical application
circuit, current flows through the switches from IN1 and IN2
to OUT
x toward the load.
UNDERVOLTAGE LOCKOUT (UVLO)
Undervoltage Lockout (UVLO) prevents the MOSFET switch-
es from turning on until the input voltage exceeds a typical
value of 1.8V.
If the input voltage drops below the UVLO threshold, the
MOSFET switches are opened and fault flags are activated.
UVLO flags function only when one or more of the ports is
enabled. Due to the paired nature of the design, both FLAG1
and FLAG2 will assert if either port1 or port2 is enabled in a
UVLO condition.
CURRENT LIMIT AND FOLDBACK
The current limit circuit is designed to protect the system sup-
ply, the LM3543 switches, and the load from potential damage
resulting from excessive currents. If a direct short occurs on
an output of the LM3543, the input capacitor(s) rapidly dis-
charge through the part, activating current limit circuitry. The
threshold for activating current limiting is 2.0A (typ.). Protec-
tion is achieved by momentarily opening the MOSFET switch
and then gradually turning it on. Turn-on is halted when the
current through the switch reaches the current-limit level of
1.0A (typ.) The current is held at this level until either the ex-
cessive load/short is removed or the part overheats and ther-
mal shutdown occurs (see Thermal Shutdown section,
below). The fault flag of a switch is asserted whenever the
switch is current limiting.
If a port on the LM3543 is enabled into a short condition, the
output current of that port will rise to the current-limit level and
hold there.
When a port is in a current-limit condition, the LM3543 senses
the output voltage on that port and, if it is less than 1.0V (typ.),
will reduce the output current through that port. This operation
is shown in Figure 2, below. The current reduction, or fold-
back, reduces power dissipation through the overloaded
MOSFET switch. An additional advantage of the foldback
feature is the reduction of power required from the source
supply when one or more output ports are shorted.
10125817
FIGURE 2. Short-Circuit Output Current (with Foldback)
vs. Output Voltage
THERMAL SHUTDOWN
The LM3543 is internally protected against excessive power
dissipation by a two-stage thermal protection circuit. If the
device temperature rises to approximately 145°C, the thermal
shutdown circuitry turns off any switch that is current limited.
Non-overloaded switches continue to function normally. If the
die temperature rises above 160°C, all switches are turned
off and all three fault flag outputs are activated. Hysteresis
ensures that a switch turned off by thermal shutdown will not
be turned on again until the die temperature is reduced to
135°C. Shorted switches will continue to cycle off and on, due
to the rising and falling die temperature, until the short is re-
moved.
The thermal shutdown function is shown graphically in Figure
www.national.com
8
101258 Version 5 Revision 6
Print Date/Time: 2010/02/04 15:48:33
LM3543
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相关代理商/技术参数 |
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| LM3544 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Quad Port USB Power Distribution Switch and Over-Current Protection |
| LM3544B-H E WAF | 制造商:Texas Instruments 功能描述: |
| LM3544M-H | 制造商:Texas Instruments 功能描述:2-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO16 |
| LM3544M-H/NOPB | 功能描述:IC USB QUAD PORT SWITCH 16-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 电源分配开关 系列:- 特色产品:XRP252 Switches 标准包装:1 系列:- 类型:高端开关 输出数:2 Rds（开）:140 毫欧 内部开关:是 电流限制:1.15A 输入电压:1.75 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:10-WFDFN 裸露焊盘 供应商设备封装:10-TDFN（3x3） 包装:Digi-Reel® 其它名称:1016-1691-6 |
| LM3544M-L | 功能描述:电源开关 IC - USB RoHS:否 制造商:Micrel 电源电压-最小:2.7 V 电源电压-最大:5.5 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:SOIC-8 封装:Tube |
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