- 您现在的位置：买卖IC网 > PDF目录44546 > LM25066PSQ (NATIONAL SEMICONDUCTOR CORP) POWER SUPPLY SUPPORT CKT, QCC24 PDF资料下载
参数资料
| 型号： | LM25066PSQ |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 电源管理 |
| 英文描述： | POWER SUPPLY SUPPORT CKT, QCC24 |
| 封装： | LLP-24 |
| 文件页数： | 11/48页 |
| 文件大小： | 1456K |
| 代理商： | LM25066PSQ |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页当前第11页第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页第33页第34页第35页第36页第37页第38页第39页第40页第41页第42页第43页第44页第45页第46页第47页第48页
cycles). The MOSFET manufacturer should be consulted for
guidelines.
- R
DS(on) should be sufficiently low such that the power dissi-
pation at maximum load current (I
LIM
2
x R
DS(on)) does not raise
its junction temperature above the manufacturer’s recom-
mendation.
- The gate-to-source voltage provided by the LM25066 can
be as high as 18.8V at turn-on when the output voltage is zero.
At turn-off, the reverse gate-to-source voltage will be equal to
the output voltage at the instant the GATE pin is pulled low.
If the device chosen for Q
1 is not rated for these voltages, an
external zener diode must be added from its gate to source,
with the zener voltage less than the device maximum V
GS
rating. The zener diode’s working voltage protects the MOS-
FET during turn-on, and its forward voltage protects the MOS-
FET during shutoff. The zener diode’s forward current rating
must be at least 190 mA to conduct the GATE pull-down cur-
rent when a circuit breaker condition is detected.
CURRENT LIMIT (R
S)
The LM25066 monitors the current in the external MOSFET
Q
1 by measuring the voltage across the sense resistor (RS),
connected from VIN to SENSE. The required resistor value is
calculated from:
(1)
where I
LIM is the desired current limit threshold. If the voltage
across R
S reaches VCL, the current limit circuit modulates the
gate of Q
1 to regulate the current at ILIM. While the current
limiting circuit is active, the fault timer is active as described
in the Fault Timer & Restart section. For proper operation,
R
S must be less than 200 m.
V
CL can be set to either 25mV or 46mV via hardware and/or
software. This setting defaults to use of CL pin which when
grounded is 25mV or high is 46mV. The value when powered
can
be
set
via
PMBus
with
the
MFR_SPECIFIC_DEVICE_SETUP command, which de-
faults to the 25mV setting.
Once the desired setting is known, calculate the shunt based
on that input voltage and maximum current. While the maxi-
mum load current in normal operation can be used to deter-
mine the required power rating for resistor R
S, basing it on the
current limit value provides a more reliable design since the
circuit can operate near the current limit threshold continu-
ously. The resistor’s surge capability must also be considered
since the circuit breaker threshold is 1.8 or 3.6 times the cur-
rent limit threshold.
Connections from R
S to the LM25066 should be made using
Kelvin techniques. In the suggested layout of Figure 7, the
small pads at the lower corners of the sense resistor connect
only to the sense resistor terminals and not to the traces car-
rying the high current. With this technique, only the voltage
across the sense resistor is applied to VIN and SENSE, elim-
inating the voltage drop across the high current solder con-
nections.
30115819
FIGURE 7. Sense Resistor Connections
POWER LIMIT THRESHOLD
The LM25066 determines the power dissipation in the exter-
nal MOSFET (Q
1) by monitoring the drain current (the current
in R
S), and the VDS of Q1 (SENSE to OUT pins). The resistor
at the PWR pin (R
PWR) sets the maximum power dissipation
for Q
1 and is calculated from the following equation:
R
PWR = 1.71 x 10
5
x R
S x PMOSFET(LIM)
(2)
where P
MOSFET(LIM) is the desired power limit threshold for
Q
1 and RS is the current sense resistor described in the Cur-
rent Limit section. For example, if R
S is 10 m and the desired
power limit threshold is 20W, R
PWR calculates to 34.2 k. If
Q
1’s power dissipation reaches the threshold, Q1’s gate is
controlled to regulate the load current, keeping Q
1’s power
from exceeding the threshold. For proper operation of the
power limiting feature, R
PWR must be ≤150 k. While the
power limiting circuit is active, the fault timer is active as de-
scribed in the Fault Timer & Restart section. Typically, power
limit is reached during startup, or if the output voltage falls
because of a severe overload or short circuit. The pro-
grammed maximum power dissipation should have a reason-
able margin from the maximum power defined by the SOA
chart, especially if retry is enabled since the MOSFET will be
repeatedly stressed during fault restart cycles. The MOSFET
manufacturer should be consulted for guidelines. If the appli-
cation does not require use of the power limit function, the
PWR pin can be left open. The accuracy of the power limit
function at turn-on may degrade if a very low value power
dissipation limit is set. The reason for this caution is that the
voltage across the sense resistor, which is monitored and
regulated by the power limit circuit, is lowest at turn-on when
19
www.national.com
LM25066
相关PDF资料 |
PDF描述 |
|---|---|
| LM25574Q0MT | SWITCHING REGULATOR, PDSO16 |
| LM25574Q0MTX | SWITCHING REGULATOR, PDSO16 |
| LM25576Q0MH | SWITCHING REGULATOR, PDSO20 |
| LM2574HVADJMWC | 1.8 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, UUC |
| LM2574HVN-3.3/NOPB | 1.8 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, PDIP8 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM25066PSQ/NOPB | 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 |
| LM25066PSQE/NOPB | 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 |
| LM25066PSQX/NOPB | 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 |
| LM25069 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Positive Low Voltage Power Limiting Hot Swap Controller |
| LM25069MM-2EVAL | 功能描述:BOARD EVALUATION LM25069 RoHS:是 类别:编程器，开发系统 >> 评估演示板和套件 系列:- 标准包装:1 系列:PCI Express® (PCIe) 主要目的:接口，收发器，PCI Express 嵌入式:- 已用 IC / 零件:DS80PCI800 主要属性:- 次要属性:- 已供物品:板 |
发布紧急采购，3分钟左右您将得到回复。