- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄384601 > LM5008 (National Semiconductor Corporation) High Voltage (100V) Step Down Switching Regulator PDF資料下載
參數(shù)資料
| 型號： | LM5008 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | High Voltage (100V) Step Down Switching Regulator |
| 中文描述： | 高電壓（100V的）降壓開關(guān)穩(wěn)壓器 |
| 文件頁數(shù)： | 12/15頁 |
| 文件大?。?/td> | 278K |
| 代理商： | LM5008 |
Applications Information
(Continued)
supply this average load current during the maximum on-
time. To keep the input voltage ripple to less than 2V (for this
exercise), C1 calculates to:
Quality ceramic capacitors in this value have a low ESR
which adds only a few millivolts to the ripple. It is the capaci-
tance which is dominant in this case. To allow for the capaci-
tor’s tolerance, temperature effects, and voltage effects, a
1.0 μF, 100V, X7R capacitor will be used.
C4:
The recommended value is 0.01μF for C4, as this is
appropriate in the majority of applications. A high quality
ceramic capacitor, with low ESR is recommended as C4
supplies the surge current to charge the buck switch gate at
turn-on. A low ESR also ensures a quick recharge during
each off-time. At minimum Vin, when the on-time is at maxi-
mum, it is possible during start-up that C4 will not fully
recharge during each 300 ns off-time. The circuit will not be
able to complete the start-up, and achieve output regulation.
This can occur when the frequency is intended to be low
(e.g., R
= 500K). In this case C4 should be increased so
it can maintain sufficient voltage across the buck switch
driver during each on-time.
C5:
This capacitor helps avoid supply voltage transients and
ringing due to long lead inductance at V
. A low ESR, 0.1μF
ceramic chip capacitor is recommended, located close to the
LM5008.
FINAL CIRCUIT
The final circuit is shown in
Figure 13
. The circuit was tested,
and the resulting performance is shown in
Figure 6
through
Figure 8
.
PC BOARD LAYOUT
The LM5008 regulation and over-voltage comparators are
very fast, and as such will respond to short duration noise
pulses. Layout considerations are therefore critical for opti-
mum performance. The components at pins 1, 2, 3, 5, and 6
should be as physically close as possible to the IC, thereby
minimizing noise pickup in the PC tracks. The current loop
formed by D1, L1, and C2 should be as small as possible.
The ground connection from C2 to C1 should be as short
and direct as possible.
If the internal dissipation of the LM5008 produces excessive
junction temperatures during normal operation, good use of
the pc board’s ground plane can help considerably to dissi-
pate heat. The exposed pad on the bottom of the LLP-8
package can be soldered to a ground plane on the PC board,
and that plane should extend out from beneath the IC to help
dissipate the heat. Additionally, the use of wide PC board
traces, where possible, can also help conduct heat away
from the IC. Judicious positioning of the PC board within the
end product, along with use of any available air flow (forced
or natural convection) can help reduce the junction
temperatures.
20097922
FIGURE 13. LM5008 Example Circuit
L
www.national.com
12
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM5008MM | High Voltage (100V) Step Down Switching Regulator |
| LM5008SD | High Voltage (100V) Step Down Switching Regulator |
| LM6118 | Fast Settling Dual Operational Amplifiers |
| LM6218AN | Fast Settling Dual Operational Amplifiers |
| LM6218N | Fast Settling Dual Operational Amplifiers |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM5008_09 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:High Voltage (100V) Step Down Switching Regulator |
| LM5008A | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:100V, 350 mA Constant On-Time Buck Switching Regulator |
| LM5008AEVAL/NOPB | 功能描述:電源管理IC開發(fā)工具 LM5008A EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| LM5008AMM | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:100V, 350 mA Constant On-Time Buck Switching Regulator |
| LM5008AMM/NOPB | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 100V,350Ma Buck 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 安裝風格:SMD/SMT |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。