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參數(shù)資料
| 型號： | LT1432 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | 5V High Efficiency Step-Down Switching Regulator Controller |
| 中文描述： | 5V的高效率降壓型開關(guān)穩(wěn)壓控制器 |
| 文件頁數(shù)： | 20/28頁 |
| 文件大?。?/td> | 611K |
| 代理商： | LT1432 |
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LT1432
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boards, their maximum rated current must also be consid-
ered. For currents greater than 1A, multiple vias may have
to be used.
4. The catch diode has large square wave currents
flowing in it. Connect the anode directly to the ground
plane and the cathode directly to the IC ground pin.
5. The ground pin of the LT1432 is the reference point
for output voltage. It should be routed separately to power
ground as near to the load as is reasonable.
Transient Response
Load transient response may be important in portable
applications where parts of the system are switched on
and off to save power. There are two types of problems
that differ by time scale. The first occurs very rapidly and
is caused by the surge current created in charging the
supply bypass capacitors on the switched load. This can
be a very serious problem if large (>0.1
μ
F) capacitors
must be charged. No regulator can respond fast enough to
handle the surge if the load switch on-resistance is low and
it is driven quickly. The solution here is to limit the rise time
of the switch drive so that the load rise time is limited to
approximately 25
×
C
LOAD
. A 1
μ
F load capacitor would
require a 25
μ
s load rise time, etc. This limits surge to
about 200mA. This time frame is still too quick for a
switching regulator to adjust to, but the surge is limited to
a low enough value that the output capacitor will attenuate
the surge voltage to an acceptable level.
A second problem is the change in DC load current.
Switching regulators take many switching cycles to re-
spond to sudden output load changes. During this time,
the output shifts by an amount equal to
load (ESR + t/C),
where ESR is the series resistance of the output capacitor,
t is the time for the regulator to shift output current, and C
is the output capacitor value. For example, if the load
change is 0.5A, ESR is 0.1
, t is 30
μ
s, and C = 390
μ
F, the
shift in output voltage would be:
V
= 0.5A
30 s
390 F
0.088V
OUT
0 1
+
=
100mV output ripple on the main capacitor will be reduced
to (0.083)(100) = 8.3mV at the output of the filter.
Layout Considerations
Although buck converters are fairly tolerant with regard to
layout issues, there are still several important things to
keep in mind. Most of these revolve around spikes created
by switching high currents at high speeds. If 3A of current
is switched in 30ns, the rate of change of current is 10E8
A/S. Voltage generated across wires will be equal to this
rate multiplied by the approximate 20nH per inch of wire.
This calculates to 2V per inch of wire or trace!! Needless
to say, connections should be kept short if the circuitry
connected to these lines is sensitive to narrow spikes.
1. The input bypass capacitor must be kept as close to
the switcher IC as possible, and its ground return must go
directly to the ground plane with no other component
grounds tied to it. The output capacitor should also
connect directly to the ground plane.
2. The frequency compensation components shown in
Figure 1 (R1 + C4, and C5) and the feedback pin bypass
capacitor (C6) are shown connected to the floating ground
pin of the IC switcher. This ground pin is also the high
current path for the switch. To avoid differential spikes
being coupled into the V
C
and FB pins, these components
must tie together and then be connected through a direct
trace to the IC switcher ground pin. No other components
should be connected anywhere on this trace and the trace
area should be minimized. A separate wide trace must be
used to connect the IC ground pin to the catch diode and
inductor. Smaller traces can be used to connect the
floating supply capacitor (C3) and the diode pin of the
LT1432 to the wide trace reasonably close to the IC ground
pin.
3. Traces which carry high current must be sized
correctly. To limit temperature rise to 20
°
C, using 1oz
copper, the trace width must be 20 mils for each ampere
of current. 1/2oz copper requires 30 mils/A. These high
current paths include the IC switcher ground pin and
switch pin, the inductor, the catch diode, the current limit
sense resistor, and the input bypass capacitor. If vias are
used to connect these components on multiple layer
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LT1432-3.3 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LT1432CN8 | 5V High Efficiency Step-Down Switching Regulator Controller |
| LT1432CN8-3.3 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LT1432CS8 | 5V High Efficiency Step-Down Switching Regulator Controller |
| LT1432CS8-3.3 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT1432-3.3 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:3.3V High Efficiency Step-Down Switching Regulator Controller |
| LT1432CN8 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:5V High Efficiency Step-Down Switching Regulator Controller |
| LT1432CN8-3.3 | 功能描述:IC REG CTRLR BUCK PWM 8-DIP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| LT1432CS8 | 制造商:Linear Technology 功能描述: |
| LT1432CS8-3.3 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:3.3V High Efficiency Step-Down Switching Regulator Controller |
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