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參數(shù)資料
| 型號： | LT1432CN8-3.3 |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| 中文描述： | SWITCHING CONTROLLER, PDIP8 |
| 封裝： | 0.300 INCH, PLASTIC, DIP-8 |
| 文件頁數(shù)： | 23/28頁 |
| 文件大?。?/td> | 611K |
| 代理商： | LT1432CN8-3.3 |
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LT1432
U
S
A
O
PPLICATI
U
U
+
–
AUXILIARY
WINDING
AUXILIARY
OUTPUT
+5V OUTPUT
D1
+
+
L1
MAIN
WINDING
+
+
+
+
POSITIVE
REGULATED
OUTPUT
NEGATIVE
REGULATED
OUTPUT
POSITIVE
REGULATOR
POSITIVE
REGULATOR
LT1432 F20
Figure 20
Figure 20 shows how to connect the auxiliary windings.
Dots indicate winding polarity. Pay attention here -- his-
tory shows that with a 50% chance of connecting up the
auxiliary correctly when you ignore the dots, in actual
practice you will be wrong 90% of the time.
The floating output can have either end grounded, depend-
ing on the need for a positive or negative output. Also
shown are the connections for both positive and negative
outputs using a linear regulator. Note that the two circuits
are identical! The floating auxiliary winding allows the use
of a positive low-dropout regulator for negative outputs.
These positive regulators are more readily available, espe-
cially at lower current levels.
There is a way to “cheat” somewhat on auxiliary power for
positive outputs higher than the 5V main output. The
auxiliary winding return can be connected to the 5V
output. This reduces the winding voltage so that more
current is available, and at the same time it actually adds
a load to the 5V output to bootstrap itself. Figure 21 shows
maximum current out of a 14V auxiliary (used to power a
12V linear regulator) connected in this fashion. The aux-
iliary winding voltage is actually 9V. Note that for lighter 5V
loads, there is an inflection point in the curves at about
11V. That is because theoretically the bootstrapping effect
should allow one to draw unlimited power from the
auxiliary winding when duty cycle exceeds 50%. The
actual available current above 50% duty cycle is limited by
parasitic losses. At high 5V loads, the inflection disap-
pears for the same reason. The curves asymptotically
approach 1 amp at high input voltage because the criteria
used to generate the curves was a drop in auxiliary output
voltage to 13.5V, and again parasitic resistance limits
output current.
Auxiliary windings deliver current in triangular or quasi-
square waves only during switch off time. Therefore the
amplitude of these pulses will be somewhat higher than
the DC auxiliary load current, especially at low input
voltage. This means that in the “stacked” connection,
ripple voltage on the 5V output will increase with auxiliary
load current.
INPUT VOLTAGE (V)
8
0
1
0.2
0.4
0.6
0.8
1.0
10
12
14
16
LT1432 F21
18
20
14V LOAD INCREASED
UNTIL V = 13.5V
I(+5) = 1A
I(+5) = 400mA
I(+5) = 200mA
I(+5) = 200mA
I(+5) = 50mA
Figure 21
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
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| LT1436 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:4.5A, 500kHz Step-Down Switching Regulator |
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