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參數(shù)資料
| 型號(hào)： | LM5010AHMHX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類(lèi)： | 穩(wěn)壓器 |
| 英文描述： | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| 中文描述： | 1.5 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封裝： | TSSOP-14 |
| 文件頁(yè)數(shù)： | 18/18頁(yè) |
| 文件大?。?/td> | 399K |
| 代理商： | LM5010AHMHX |
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capacitor’s ESR is insufficient additional series resistance
may be required (R3 in the Block Diagram).
The LM5010A operates in continuous conduction mode at
heavy load currents, and discontinuous conduction mode at
light load currents. In continuous conduction mode current al-
ways flows through the inductor, never decaying to zero
during the off-time. In this mode the operating frequency re-
mains relatively constant with load and line variations. The
minimum load current for continuous conduction mode is one-
half the inductor’s ripple current amplitude. The operating
frequency in the continuous conduction mode is calculated as
follows:
(2)
The buck switch duty cycle is equal to:
(3)
Under light load conditions, the LM5010A operates in discon-
tinuous conduction mode, with zero current flowing through
the inductor for a portion of the off-time. The operating fre-
quency is always lower than that of the continuous conduction
mode, and the switching frequency varies with load current.
Conversion efficiency is maintained at a relatively high level
at light loads since the switching losses diminish as the power
delivered to the load is reduced. The discontinuous mode op-
erating frequency is approximately:
(4)
where R
L = the load resistance.
Start-Up Bias Regulator (V
CC)
A high voltage bias regulator is integrated within the
LM5010A. The input pin (VIN) can be connected directly to
line voltages between 6V and 75V. Referring to the block di-
agram and the graph of V
CC vs. VIN, when VIN is between 6V
and the bypass threshold (nominally 8.9V), the bypass switch
(Q2) is on, and V
CC tracks VIN within 100 mV to 150 mV. The
bypass switch on-resistance is approximately 50
, with in-
herent current limiting at approximately 100 mA. When VIN is
above the bypass threshold, Q2 is turned off, and V
CC is reg-
ulated at 7V. The V
CC regulator output current is limited at
approximately 15 mA. When the LM5010A is shutdown using
the RON/SD pin, the V
CC bypass switch is shut off, regardless
of the voltage at VIN.
When V
IN exceeds the bypass threshold, the time required for
Q2 to shut off is approximately 2 - 3 s. The capacitor at VCC
(C3) must be a minimum of 0.47 F to prevent the voltage at
VCC from rising above its absolute maximum rating in re-
sponse to a step input applied at VIN. C3 must be located as
close as possible to the LM5010A pins.
In applications with a relatively high input voltage, power dis-
sipation in the bias regulator is a concern. An auxiliary voltage
of between 7.5V and 14V can be diode connected to the VCC
pin (D2 in Figure 2) to shut off the VCC regulator, reducing
internal power dissipation. The current required into the VCC
pin is shown in the Typical Performance Characteristics. In-
ternally a diode connects VCC to VIN requiring that the aux-
iliary voltage be less than V
IN.
The turn-on sequence is shown in Figure 1. When VCC ex-
ceeds the under-voltage lock-out threshold (UVLO) of 5.25V
(t1 in Figure 1), the buck switch is enabled, and the SS pin is
released to allow the soft-start capacitor (C6) to charge up.
The output voltage V
OUT is regulated at a reduced level which
increases to the desired value as the soft-start voltage in-
creases (t2 in Figure 1).
20153816
FIGURE 2. Self Biased Configuration
Regulation Comparator
The feedback voltage at the FB pin is compared to the voltage
at the SS pin (2.5V, ±2%). In normal operation an on-time
period is initiated when the voltage at FB falls below 2.5V. The
buck switch conducts for the on-time programmed by R
ON,
causing the FB voltage to rise above 2.5V. After the on-time
period the buck switch remains off until the FB voltage falls
below 2.5V. Input bias current at the FB pin is less than 5 nA
over temperature.
Over-Voltage Comparator
The feedback voltage at FB is compared to an internal 2.9V
reference. If the voltage at FB rises above 2.9V the on-time
is immediately terminated. This condition can occur if the in-
9
www.national.com
LM5010A
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM5010AMH | 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM5010AMH/NOPB | 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 Hi Volt 1A Step Down Switching Reg RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM5010AMHE | 制造商:Texas Instruments 功能描述:Conv DC-DC Single Step Down 6V to 75V 14-Pin TSSOP EP T/R |
| LM5010AMHE/NOPB | 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM5010AMHX | 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
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