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參數(shù)資料
| 型號： | LM5010AHMHX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 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 |
| 文件頁數(shù)： | 3/18頁 |
| 文件大?。?/td> | 399K |
| 代理商： | LM5010AHMHX |
20153820
FIGURE 4. Inductor Current - Current Limit Operation
N - Channel Buck Switch and Driver
The LM5010A integrates an N-Channel buck switch and as-
sociated floating high voltage gate driver. The peak current
through the buck switch should not exceed 2A, and the load
current should not exceed 1.5A. The gate driver circuit is
powered by the external bootstrap capacitor between BST
and SW (C4), which is recharged each off-time from V
CC
through the internal high voltage diode. The minimum off-
time, nominally 260 ns, ensures sufficient time during each
cycle to recharge the bootstrap capacitor. A 0.022 F ceramic
capacitor is recommended for C4.
Soft-start
The soft-start feature allows the regulator to gradually reach
a steady state operating point, thereby reducing startup
stresses and current surges. At turn-on, while V
CC is below
the under-voltage threshold (t1 in Figure 1), the SS pin is in-
ternally grounded, and V
OUT is held at 0V. When VCC exceeds
the under-voltage threshold (UVLO) an internal 11.5 A cur-
rent source charges the external capacitor (C6) at the SS pin
to 2.5V (t2 in Figure 1). The increasing SS voltage at the non-
inverting input of the regulation comparator gradually increas-
es the output voltage from zero to the desired value. The soft-
start feature keeps the load inductor current from reaching the
current limit threshold during start-up, thereby reducing inrush
currents.
An internal switch grounds the SS pin if V
CC is below the un-
der-voltage lock-out threshold, if a thermal shutdown occurs,
or if the circuit is shutdown using the RON/SD pin.
Thermal Shutdown
The LM5010A should be operated below the Maximum Op-
erating Junction Temperature rating. If the junction tempera-
ture increases during a fault or abnormal operating condition,
the internal Thermal Shutdown circuit activates typically at
175°C. The Thermal Shutdown circuit reduces power dissi-
pation by disabling the buck switch and the on-timer, and
grounding the SS pin. This feature helps prevent catastrophic
failures from accidental device overheating. When the junc-
tion temperature reduces below approximately 155°C (20°C
typical hysteresis), the SS pin is released and normal opera-
tion resumes.
Applications Information
EXTERNAL COMPONENTS
The procedure for calculating the external components is il-
lustrated with a design example. Referring to the Block Dia-
gram, the circuit is to be configured for the following
specifications:
V
OUT = 5V
V
IN = 6V to 60V
F
S = 175 kHz
Minimum load current = 200 mA
Maximum load current = 1.0A
Softstart time = 5 ms.
R1 and R2:
These resistors set the output voltage, and their
ratio is calculated from:
R1/R2 = (V
OUT/2.5V) - 1
(10)
R1/R2 calculates to 1.0. The resistors should be chosen from
standard value resistors in the range of 1.0 k
- 10 k. A value
of 1.0 k
will be used for R1 and for R2.
R
ON, FS: R
ON can be chosen using Equation 7 to set the nom-
inal frequency, or from Equation 6 if the on-time at a particular
V
IN is important. A higher frequency generally means a small-
er inductor and capacitors (value, size and cost), but higher
switching losses. A lower frequency means a higher efficien-
cy, but with larger components. Generally, if PC board space
is tight, a higher frequency is better. The resulting on-time and
frequency have a ±25% tolerance. Using equation 7 at a
nominal V
IN of 8V,
A value of 200 k
will be used for R
ON, yielding a nominal
frequency of 161 kHz at V
IN = 6V, and 205 kHz at VIN = 60V.
L1:
The guideline for choosing the inductor value in this ex-
ample is that it must keep the circuit’s operation in continuous
conduction mode at minimum load current. This is not a strict
requirement since the LM5010A regulates correctly when in
discontinuous conduction mode, although at a lower frequen-
cy. However, to provide an initial value for L1 the above
guideline will be used.
11
www.national.com
LM5010A
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| LM5010AMH | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(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/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(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/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(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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