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參數(shù)資料
| 型號： | LT1432CN8 |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 5V High Efficiency Step-Down Switching Regulator Controller |
| 中文描述： | SWITCHING CONTROLLER, PDIP8 |
| 封裝： | PLASTIC, DIP-8 |
| 文件頁數(shù)： | 21/28頁 |
| 文件大?。?/td> | 611K |
| 代理商： | LT1432CN8 |
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21
LT1432
Figure 17 shows the effect of a 500mA transient load (0.3A
to 0.8A) on the LT1432, both with and without an output
filter. The top trace with no filter shows about a 60mV
deviation with a settling time of 300
μ
s. Astute switching
regulator designers may notice the lack of switching ripple
in this trace. To make a clean display the actual trace was
fed through a one pole filter with 16
μ
s time constant to
eliminate most of the switching ripple. This had very little
effect on the shape or amplitude of the response waveform
(you’ll have to trust me on this one). In the middle trace,
an output filter of 10
μ
H and 200
μ
F was added to the
regulator to achieve very low output ripple. The load
transient response is obviously degraded because the
second filter capacitor, following normal design practice,
is somewhat smaller than the main output capacitor, and
therefore also has higher ESR. Note the slight ringing
caused by the “Q” of the output filter. Calculated ringing
frequency is 1/(2
π
√
LC) = 3.4kHz. Also note the small step
in DC level between the two load conditions on the filtered
output. To maintain good loop stability, the added filter is
left “outside” the feedback loop. Therefore, the DC resis-
tance of the 10
μ
H inductor will add to load regulation. The
10mV step implies a resistance of 10mV/0.5A = 0.02
.
The message in all this is to be careful when adding output
filters if transient load response or load regulation is
critical. The second filter capacitor may have to be as large
as the main filter capacitor.
U
S
A
O
PPLICATI
U
U
Mode Pin Drive
The mode pin defines operating conditions for the LT1432.
A low state programs the IC to operate in “normal” mode
as a constant frequency, current mode, buck converter.
Floating the pin converts the internal error amplifier to a
comparator which puts the LT1432 into a low-power
“burst” mode. In this mode, the pin assumes an open
circuit voltage of approximately 1V. To ensure stable
operation, current into or out of the pin must be limited to
2
μ
A. If the pin is routed near any switching or logic signals
it should be bypassed with a 200pF capacitor to avoid
pickup.
Driving the mode pin high causes the LT1432 to go into
complete shutdown. An internal resistor limits mode pin
current to about 15
μ
A at 5V. A 7V zener diode is also in
parallel with the pin, so input voltages higher than 6.5V
must be externally limited with a resistor. The current/
voltage characteristics of the mode pin are shown in
Typical Performance Characteristics. Note that the drive
signal must sink about 30
μ
A when pulling the mode pin to
its worst case low threshold of 0.6V. This should not be a
problem for any standard open drain or three-state output.
If all three states are desired and a three-state drive is not
available, the circuit shown in Figure 18 can be used. Two
separate logic inputs are used. Both low will allow the
mode pin to float for burst mode. “A” high, “B” low will
generate shutdown, and “B” high, “A” low forces normal
mode operation. Both high will also force normal mode
operation, but this is not an intended state and R1 is
included to limit overload of “A” if this occurs. C1 is
suggested if the mode pin line can pick up capacitively
coupled stray switching or logic signals.
100mV/DIV
100mV/DIV
0.5A/DIV
0.5ms/DIV
TO
MODE PIN
C1
200pF
VN2222L
R1
10k
D1
1N914
LT1432 F18
A
B
Figure 18. Two Input Mode Drive
Figure 17
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| LT1432CS8 | 5V High Efficiency Step-Down Switching Regulator Controller |
| LT1432CS8-3.3 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 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 |
| LT1435 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:4.5A, 500kHz Step-Down Switching Regulator |
| 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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