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參數(shù)資料
| 型號(hào)： | LM3100MH |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類(lèi)： | 穩(wěn)壓器 |
| 英文描述： | SIMPLE SWITCHER㈢ Synchronous 1MHz 1.5A Step-Down Voltage Regulator |
| 中文描述： | 1.9 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | PLASTIC, TSSOP-20 |
| 文件頁(yè)數(shù)： | 12/15頁(yè) |
| 文件大?。?/td> | 1073K |
| 代理商： | LM3100MH |
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N - Channel Buck Switch and
Driver
The LM3100 integrates an N-Channel buck (high-side)
switch and associated floating high voltage gate driver. The
gate drive circuit works in conjunction with an external boot-
strap capacitor and an internal high voltage diode. A 33 nF
capacitor (C
) connected between BST and SW pins pro-
vides voltage to the high-side driver during the buck switch
on-time. During each off-time, the SW pin falls to approxi-
mately -1V and C
charges from the V
supply through
the internal diode. The minimum off-time of 260ns ensures
adequate time each cycle to recharge the bootstrap capaci-
tor.
Softstart
The soft-start feature allows the converter to gradually reach
a steady state operating point, thereby reducing start-up
stresses and current surges. Upon turn-on, after V
CC
reaches the under-voltage threshold, an internal 8μA current
source charges up the external capacitor at the SS pin. The
ramping voltage at SS (and the non-inverting input of the
regulation comparator) ramps up the output voltage in a
controlled manner.
An internal switch grounds the SS pin if V
is below the
under-voltage lockout threshold, if a thermal shutdown oc-
curs, or if the EN pin is grounded. Using an externally
controlled switch, the output voltage can be shut off by taking
the SS pin to ground. Releasing the switch allows the SS pin
to ramp up, and the output voltage to return to normal. The
shut-down configuration is shown in Figure 3.
Thermal Protection
The LM3100 should be operated so the junction temperature
does not exceed the maximum limit. An internal Thermal
Shutdown circuit, which activates (typically) at 165C, takes
the controller to a low power reset state by disabling the buck
switch and the on-timer, and grounding the Softstart pin. This
feature helps prevent catastrophic failures from accidental
device overheating. When the junction temperature falls
back below 145C (typical hysteresis = 20C), the Softstart
pin is released and normal operation resumes.
Applications Information
EXTERNAL COMPONENTS
The following guidelines can be used to select the external
components.
R
FB1
and R
FB2
: The ratio of these resistors is calculated
from:
R
FB1
/R
FB2
= (V
OUT
/0.8V) - 1
R
and R
should be chosen from standard value resis-
tors in the range of 1.0 k
- 10 k
which satisfy the above
ratio.
For V
= 0.8V, the FB pin can be connected to the output
directly. However, the converter operation needs a minimum
inductor current ripple to maintain good regulation when no
load is connected. This minimum load is about 10 μA and
can be implemented by adding a pre-load resistor to the
output.
R
ON
:
The minimum value for RON is calculated from:
Equation 1 can be used to select R
ON
if a specific frequency
is desired as long as the above limitation is met.
L:
The main parameter effected by the inductor is the output
current ripple amplitude (I
OR
). The maximum allowable (I
OR
must be determined at both the minimum and maximum
nominal load currents. At minimum load current, the lower
peak must not reach 0 mA. At maximum load current, the
upper peak must not exceed the current limit threshold
(1.9A). The allowable ripple current is calculated from the
following equations:
I
OR(MAX1)
= 2 x I
O(min)
or
I
OR(MAX2)
= 2 x (1.9A - I
O(max)
)
The lesser of the two ripple amplitudes calculated above is
then used in the following equation:
(7)
where V
is the maximum input voltage and Fs is deter-
mined from equation 1. This provides a value for L. The next
larger standard value should be used. L should be rated for
the I
PK
current level shown in Figure 2.
Inductor Selector for V
OUT
= 3.3V
20174736
20174706
FIGURE 3. Alternate Shutdown Implementation
L
www.national.com
12
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3100MH/NOPB | 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 SYNC 1MHZ 1.5A STEP- DOWN VLTG 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 |
| LM3100MHX | 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 |
| LM3100MHX/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 |
| LM3101 | 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:Secondary-Side PWM Controller |
| LM3101M | 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:Secondary-Side PWM Controller |
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