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参数资料
| 型号： | LM3151MHE-2.5 |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 250 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封装： | TSSOP-14 |
| 文件页数： | 2/20页 |
| 文件大小： | 479K |
| 代理商： | LM3151MHE-2.5 |
The valley current limit feature prevents current runaway con-
ditions due to propagation delays or inductor saturation since
the inductor current is forced to decay following any overload
conditions.
30053212
FIGURE 1. Inductor Current - Current Limit Operation
Short-Circuit Protection
The LM3151/2/3 will sense a short-circuit on the output by
monitoring the output voltage. When the attenuated feedback
voltage has fallen below 60% of the reference voltage, V
ref x
0.6 (
≈ 0.36V), short-circuit mode of operation will start. During
short-circuit operation, the SS pin is discharged and the out-
put voltage will fall to 0V. The SS pin voltage, V
SS, is then
ramped back up at the rate determined by the SS capacitor
and I
SS until VSS reaches 0.7V. During this re-ramp phase, if
the short-circuit fault is still present the output current will be
equal to the set current limit. Once the soft-start voltage
reaches 0.7V the output voltage is sensed again and if the
attenuated V
FB is still below Vref x 0.6 then the SS pin is dis-
charged again and the cycle repeats until the short-circuit fault
is removed.
Soft-Start
The soft-start (SS) feature allows the regulator to gradually
reach a steady-state operating point, which reduces start-up
stresses and current surges. At turn-on, while VCC is below
the under-voltage threshold, the SS pin is internally grounded
and V
OUT is held at 0V. The SS capacitor is used to slowly
ramp V
FB from 0V to it's final output voltage as programmed
by the internal resistor divider. By changing the soft-start ca-
pacitor value, the duration of start-up can be changed ac-
cordingly. The start-up time can be calculated using the
following equation:
Where t
SS is measured in seconds, Vref = 0.6V and ISS is the
soft-start pin source current, which is typically 7.7 A (refer to
electrical characteristics table).
An internal switch grounds the SS pin if VCC is below the
under-voltage lockout threshold, if a thermal shutdown oc-
curs, or if the EN pin is grounded. By using an externally
controlled switch, the output voltage can be shut off by
grounding the SS pin.
During startup the LM3151/2/3 will operate in diode emulation
mode, where the low-side gate LG will turn off and remain off
when the inductor current falls to zero. Diode emulation mode
allows for start up into a pre-biased output voltage. When soft-
start is greater than 0.7V, the LM3151/2/3 will remain in
continuous conduction mode. During diode emulation mode
at current limit the low-gate will remain off when the inductor
current is off.
The soft start time should be greater than the rise time spec-
ified by,
t
SS ≥ (VOUT x COUT) / (IOCL - IOUT)
Enable/Shutdown
The EN pin can be activated by either leaving the pin floating
due to an internal pull up resistor to VIN or by applying a logic
high signal to the EN pin of 1.26V or greater. The LM3151/2/3
can be remotely shut down by taking the EN pin below 1.02V.
Low quiescent shutdown is achieved when V
EN is less than
0.4V. During low quiescent shutdown the internal bias circuit-
ry is turned off.
The LM3151/2/3 has certain fault conditions that can trigger
shutdown, such as over-voltage protection, current limit, un-
der-voltage lockout, or thermal shutdown. During shutdown,
the soft-start capacitor is discharged. Once the fault condition
is removed, the soft-start capacitor begins charging, allowing
the part to start up in a controlled fashion. In conditions where
there may be an open drain connection to the EN pin, it may
be necessary to add a 1000 pF bypass capacitor to this pin.
This will help decouple noise from the EN pin and prevent
false disabling.
www.national.com
10
LM3151/LM3152/LM3153
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3151MHE-3.3 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述:SIMPLE SWITCHER 6~42V 14TSSOP 制造商:Texas Instruments 功能描述:SIMPLE SWITCHER, 6~42V, 14TSSOP 制造商:Texas Instruments 功能描述:SIMPLE SWITCHER, 6~42V, 14TSSOP, Primary Input Voltage:18V, No. of Outputs:1, Output Voltage:3.3V, Output Current:12A, Voltage Regulator Case Style:TSSOP, No. of Pins:14, Operating Temperature Min:-40C, Operating Temperature , RoHS Compliant: Yes |
| LM3151MHE-3.3/NOPB | 功能描述:DC/DC 开关控制器 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 |
| LM3151MHX-3.3 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:SIMPLE SWITCHER? CONTROLLER, High Input Voltage Synchronous Step-Down |
| LM3151MHX-3.3/NOPB | 功能描述:DC/DC 开关控制器 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 |
| LM3152 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:SIMPLE SWITCHER? CONTROLLER, High Input Voltage Synchronous Step-Down |
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