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參數(shù)資料
| 型號： | LM3207TLX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers with Integrated Vref LDO |
| 中文描述： | 1.2 A SWITCHING REGULATOR, 2300 kHz SWITCHING FREQ-MAX, BGA9 |
| 封裝： | MICRO SMD, 9 PIN |
| 文件頁數(shù)： | 16/19頁 |
| 文件大?。?/td> | 1335K |
| 代理商： | LM3207TLX |
Application Information
(Continued)
LDO CAPACITOR SELECTION
The output capacitor should be connected between the LDO
output and a good ground connection. This capacitor must
be selected within specified capacitance range and have
sufficiently low ESR. The ESR of the capacitor is generally a
major factor in LDO stability. Refer to manufacturer ESR
curves for more detail.
Table 1
suggests acceptable capaci-
tors and their suppliers.
TABLE 1. Suggested capacitors and their suppliers
Model
Vendor
TDK
TDK
C1005X5R1A104KT, 100nF, 10V
C1005X5R0J224KT, 220nF, 6.3V
INDUCTOR SELECTION
A 3.3μH inductor with saturation current rating over 1200mA
and low inductance drop at the full DC bias condition is
recommended for almost all applications. The inductor’s DC
resistance should be less than 0.2
for good efficiency. For
low dropout voltage, lower DCR inductors are advanta-
geous. The lower limit of acceptable inductance is 1.7μH at
1200mAover the operating temperature range. Full attention
should be paid to this limit, because some small inductors
show large inductance drops at high DC bias. These can not
be used with the LM3207.
Table 2
suggests some inductors
and suppliers.
TABLE 2. Suggested inductors and their suppliers
Model
Size (WxLxH)
[mm]
3.0 x 3.0 x 1.5
3.3 x 3.3 x 1.4
3.2 x 2.6 x 1.0
Vendor
NR3015T3R3M
DO3314-332MXC
MIPW3226D3R0M
Taiyo-Yuden
Coilcraft
FDK
If a smaller inductance inductor is used in the application, the
LM3207 may become unstable during line and load tran-
sients and V
transient response times may be affected.
For low-cost applications, an unshielded bobbin inductor is
suggested. For noise critical applications, a toroidal or
shielded-bobbin inductor is recommended. A good practice
is to layout the board with footprints accommodating both
types for design flexibility. This allows substitution of a low-
noise toroidal inductor, in the event that noise from low-cost
bobbin models is unacceptable. Saturation occurs when the
magnetic flux density from current through the windings of
the inductor exceeds what the inductor’s core material can
support with a corresponding magnetic field. This can result
in poor efficiency, regulation errors or stress to DC-DC con-
verter like the LM3207.
DC-DC CONVERTER CAPACITOR SELECTION
The LM3207 is designed with a ceramic capacitor for its
input and output filters. Use a 10μF ceramic capacitor for
input and a 4.7μF ceramic capacitor for output. They should
maintain at least 50% capacitance at DC bias and tempera-
ture conditions. Ceramic capacitors types such as X5R, X7R
are recommended for both filters. These provide an optimal
balance between small size, cost, reliability and performance
for cell phones and similar applications.
Table 3
lists sug-
gests acceptable part numbers and their suppliers. DC bias
characteristics of the capacitors must be considered when
selecting the voltage rating and case size of the capacitor. If
it is necessary to choose a 0603-size capacitor for V
, the
operation of the LM3207should be carefully evaluated on the
system board. Output capacitors with smaller case sizes
mitigate piezo electric vibrations when the output voltage is
stepped up and down at fast rates. However, they have a
larger percentage drop in value with dc bias. Use of multiple
2.2μF or 1μF capacitors in parallel may also be considered.
TABLE 3. Suggested capacitors and their suppliers
Model
Vendor
Taiyo-Yuden
TDK
TDK
TDK
TDK
0805ZD475KA, 4.7μF, 10V
C1608X5R0J475M, 4.7uF, 6.3V
C1608X5R0J106M, 10μF, 6.3V
C2012X5R0J106M, 10uF, 6.3V
C2012X5R1A475M, 4.7uF, 6.3V
The input filter capacitor supplies AC current drawn by the
PFET switch of the LM3207 in the first part of each cycle and
reduces the voltage ripple imposed on the input power
source. The output filter capacitor absorbs the AC inductor
current, helps maintain a steady output voltage during tran-
sient load changes and reduces output voltage ripple. These
capacitors must be selected with sufficient capacitance and
sufficiently low ESR (Equivalent Series Resistance) to per-
form these functions. The ESR of the filter capacitors is
generally a factor in voltage ripple.
EN PIN CONTROL
Drive the EN and EN
LDO
pins using the system controller to
turn the LM3207 ON and OFF. Use a comparator, Schmidt
trigger or logic gate to drive the EN and EN
pins. Set EN
high (
>
1.2V) for normal operation and low (
<
0.5V) for a
0.01μA (typ.) shutdown mode.
Set EN low to turn off the LM3207 during power-up and
under voltage conditions when the power supply is less than
the 2.7V minimum operating voltage. The part is out of
regulation when the input voltage is less than 2.7V. The
LM3207 is designed for mobile phones where the system
controller controls operation mode for maximizing battery life
and requirements for small package size outweigh the addi-
tional size required for inclusion of UVLO (Under Voltage
Lock-Out) circuitry.
Micro SMD PACKAGE ASSEMBLY AND USE
Use of the Micro SMD package requires specialized board
layout, precision mounting and careful re-flow techniques, as
detailed in National Semiconductor Application Note 1112.
Refer to the section Surface Mount Technology (SMD) As-
sembly Considerations. For best results in assembly, align-
ment ordinals on the PC board should be used to facilitate
placement of the device. The pad style used with Micro SMD
package must be the NSMD (non-solder mask defined) type.
This means that the solder-mask opening is larger than the
pad size. This prevents a lip that otherwise forms if the
solder-mask and pad overlap, from holding the device off the
surface of the board and interfering with mounting. See
Application Note 1112 for specific instructions.
The 9-Bump package used for LM3207 has 300 micron
solder balls and requires 10.82mil pads for mounting the
circuit board. The trace to each pad should enter with a 90
entry angle to prevent debris from being caught in deep
corners. Initially, the trace to each pad should be 6-7mil
L
www.national.com
16
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3207TLX/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 |
| LM3207TLX-2.53 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers with Integrated Vref LDO |
| LM3207TLX-2.53/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 |
| LM3208 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers |
| LM3208TL | 制造商:Texas Instruments 功能描述:Conv DC-DC Single Step Down 2.7V to 5.5V 8-Pin uSMD T/R 制造商:Texas Instruments 功能描述:IC, BUCK, 650MA, RF PWR AMP, 8USMD |
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