- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄358828 > LM2717MTX (NATIONAL SEMICONDUCTOR CORP) Dual Step-down DC/DC Converter PDF資料下載
參數(shù)資料
| 型號(hào)： | LM2717MTX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Dual Step-down DC/DC Converter |
| 中文描述： | 3.2 A SWITCHING REGULATOR, 600 kHz SWITCHING FREQ-MAX, PDSO24 |
| 封裝： | TSSOP-24 |
| 文件頁數(shù)： | 10/12頁 |
| 文件大?。?/td> | 673K |
| 代理商： | LM2717MTX |
Buck Operation
(Continued)
BOOTSTRAP CAPACITOR
A 4.7nF ceramic capacitor or larger is recommended for the
bootstrap capacitor. For applications where the input voltage
is less than twice the output voltage a larger capacitor is
recommended, generally 0.1μF to 1μF to ensure plenty of
gate drive for the internal switches and a consistently low
R
DS(ON)
.
SOFT-START CAPACITOR (BOTH REGULATORS)
The LM2717 does not contain internal soft-start which allows
for fast startup time but also causes high inrush current.
Therefore for applications that need reduced inrush current
the LM2717 has circuitry that is used to limit the inrush
current on start-up of the DC/DC switching regulators. This
inrush current limiting circuitry serves as a soft-start. The
external SS pins are used to tailor the soft-start for a specific
application. A current (I
) charges the external soft-start
capacitor, C
SS
. The soft-start time can be estimated as:
T
SS
= C
SS
*0.6V/I
SS
When programming the softstart time simply use the equa-
tion given in the
Soft-Start Capacitor
section above.
SCHOTTKY DIODE
The breakdown voltage rating of D
1
and D
2
is preferred to be
25% higher than the maximum input voltage. The current
rating for the diode should be equal to the maximum output
current for best reliability in most applications. In cases
where the input voltage is much greater than the output
voltage the average diode current is lower. In this case it is
possible to use a diode with a lower average current rating,
approximately (1-D)*I
OUT
however the peak current rating
should be higher than the maximum load current.
Application Information
LAYOUT CONSIDERATIONS
The LM2717 uses two separate ground connections, PGND
for the drivers and boost NMOS power device and AGND for
the sensitive analog control circuitry. The AGND and PGND
pins should be tied directly together at the package. The
feedback and compensation networks should be connected
directly to a dedicated analog ground plane and this ground
plane must connect to the AGND pin. If no analog ground
plane is available then the ground connections of the feed-
back and compensation networks must tie directly to the
AGND pin. Connecting these networks to the PGND can
inject noise into the system and effect performance.
The input bypass capacitor C
IN
, as shown in
Figure 1
, must
be placed close to the IC. This will reduce copper trace
resistance which effects input voltage ripple of the IC. For
additional input voltage filtering, a 0.1μF to 4.7μF bypass
capacitors can be placed in parallel with C
, close to the V
IN
pins to shunt any high frequency noise to ground. The output
capacitors, C
and C
, should also be placed close to
the IC. Any copper trace connections for the C
capaci-
tors can increase the series resistance, which directly effects
output voltage ripple. The feedback network, resistors R
and R
, should be kept close to the FB pin, and away from
the inductor to minimize copper trace connections that can
inject noise into the system. Trace connections made to the
inductors and schottky diodes should be minimized to re-
duce power dissipation and increase overall efficiency. For
more detail on switching power supply layout considerations
seeApplication NoteAN-1149:
Layout Guidelines for Switch-
ing Power Supplies
.
Some recommended Inductors (others may be used)
Manufacturer
Coilcraft
Coiltronics
Pulse
Sumida
Inductor
Contact Information
www.coilcraft.com
www.cooperet.com
www.pulseeng.com
www.sumida.com
DO3316 and DO5022 series
DRQ73 and CD1 series
P0751 and P0762 series
Some recommended Input and Output Capacitors (others may be used)
Manufacturer
Vishay Sprague
Taiyo Yuden
Capacitor
Contact Information
www.vishay.com
www.t-yuden.com
293D, 592D, and 595D series tantalum
High capacitance MLCC ceramic
ESRD seriec Polymer Aluminum Electrolytic
SPV and AFK series V-chip series
High capacitance MLCC ceramic
EEJ-L series tantalum
Cornell Dubilier
www.cde.com
Panasonic
www.panasonic.com
L
www.national.com
10
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM2731XMF | 0.6/1.6 MHz Boost Converters With 22V Internal FET Switch in SOT-23 |
| LM2731XMFX | 0.6/1.6 MHz Boost Converters With 22V Internal FET Switch in SOT-23 |
| LM2731YMF | 0.6/1.6 MHz Boost Converters With 22V Internal FET Switch in SOT-23 |
| LM2731YMFX | 0.6/1.6 MHz Boost Converters With 22V Internal FET Switch in SOT-23 |
| LM2731 | 0.6/1.6 MHz Boost Converters With 22V Internal FET Switch in SOT-23 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM2717MTX/NOPB | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| LM2717MTX-ADJ | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| LM2717MTX-ADJ/NOPB | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| LM272 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:DUAL POWER OPERATIONAL AMPLIFIER |
| LM2720 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:5-Bit Programmable, High Frequency Multi-phase PWM Controller |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。