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參數(shù)資料
| 型號： | LM3202 |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | DC/DC變換器 |
| 英文描述： | 650mA Miniature, Adjustable, Step-Down DC-DC Converter for RF Power Amplifiers |
| 中文描述： | 六百五十零毫安微型，可調(diào)，降壓型DC - DC轉(zhuǎn)換器的射頻功率放大器 |
| 文件頁數(shù)： | 12/15頁 |
| 文件大?。?/td> | 1507K |
| 代理商： | LM3202 |
Current Limiting
(Continued)
down to approximately 0.375V, then the device switches to a
timed current limit mode. In timed current limit mode the
internal PFET switch is turned off after the current compara-
tor trips and the beginning of the next cycle is inhibited for
3.5us to force the instantaneous inductor current to ramp
down to a safe value. The synchronous rectifier is off in
timed current limit mode. Timed current limit prevents the
loss of current control seen in some products when the
output voltage is pulled low in serious overload conditions.
Dynamically Adjustable Output
Voltage
The LM3202 features dynamically adjustable output voltage
to eliminate the need for external feedback resistors. The
output can be set from V
FB,MIN
to V
FB,MAX
by changing the
voltage on the analog V
applications where peak power is needed only when the
handset is far away from the base station or when data is
being transmitted. In other instances the transmitting power
can be reduced. Hence the supply voltage to the PA can be
reduced, promoting longer battery life. See
Setting the Out-
put Voltage
in the
Application Information section
for further
details.
Thermal Overload Protection
The LM3202 has a thermal overload protection function that
operates to protect itself from short-term misuse and over-
load conditions. When the junction temperature exceeds
around 150C, the device inhibits operation. Both the PFET
and the NFET are turned off in PWM mode. When the
temperature drops below 125C, normal operation resumes.
Prolonged operation in thermal overload conditions may
damage the device and is considered bad practice.
Application Information
SETTING THE OUTPUT VOLTAGE
The LM3202 features a pin-controlled variable output volt-
age to eliminate the need for external feedback resistors. It
can be programmed for an output voltage from 1.3V (typ) to
3.16V (typ) by setting the voltage on the V
CON
pin, as in
Table 1
.
TABLE 1. Output Voltage Selection
V
CON
(V)
V
CON
≤
0.484
0.556
<
V
CON
<
1.208
V
CON
≥
1.312
V
OUT
(V)
V
FB,MIN
V
OUT
= 2.5 x V
CON
V
FB,MAX
Refer to
Figure 4
for the relation between V
OUT
and V
CON
.
When the control pin voltage is between 0.556V and 1.208V,
the output voltage will vary in a monotonic fashion with
respect to the voltage on the control pin as per the above
Table 1
equation.
Internally the control pin is clamped before it is fed to the
error amplifier inputs. If voltage on the control pin is less than
0.484V, the output voltage is regulated at V
FB,MIN
and if the
voltage is greater than 1.312V, the output is regulated at
V
FB,MAX
.
INDUCTOR SELECTION
A 3.3μH inductor with saturation current rating over 1200mA
is recommended for almost all applications. The inductor’s
resistance should be less than 0.2
for good efficiency. For
low dropout voltage, lower DCR inductors are advanta-
geous. Using inductors that drop by 20% in value at 1200mA
over the operating temp range is acceptable if needed to
select smallest inductor.
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 3.3x 1.4
Vendor
Taiyo-Yuden
Coilcraft
NR3015T3R3M
DO3314-332MXC
If smaller inductance inductor is used in the application, the
LM3202 may become unstable during line and load tran-
sients and V
CON
transient response times may get affected.
For low-cost applications, an unshielded bobbin inductor is
suggested. For noise critical applications, a toroidal or
shielded-bobbin inductor should be used. 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 cause
poor efficiency, regulation errors or stress to DC-DC con-
verter like the LM3202.
20141562
FIGURE 4. V
CON
Voltage vs Output Voltage
L
www.national.com
12
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| LM3202_06 | 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 |
| LM3202TL | 制造商:Texas Instruments 功能描述:Adj. Step-Down DC-DC Converter,LM3202TL |
| LM3202TL/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 |
| LM3202TLEV | 功能描述:電源管理IC開發(fā)工具 LM3202 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 |
| LM3202TLX | 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 |
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