參數(shù)資料
型號(hào)： LT1376I
廠商： Linear Technology Corporation
英文描述： Octal D-Type Edge-Triggered Flip-Flops with 3-State Outputs 20-SOIC 0 to 70
中文描述： 1.5A的，500kHz降壓型開關(guān)穩(wěn)壓器
文件頁(yè)數(shù)： 17/28頁(yè)
文件大?。?/td> 232K
代理商： LT1376I
17
LT1375/LT1376
APPLICATIO
S I
FOR
ATIO
U
PARASITIC RESONANCE
W
U
U
Resonance or “ringing” may sometimes be seen on the
switch node (see Figure 7). Very high frequency ringing
following switch rise time is caused by switch/diode/input
capacitor lead inductance and diode capacitance. Schot-
tky diodes have very high “Q” junction capacitance that
can ring for many cycles when excited at high frequency.
If total lead length for the input capacitor, diode and switch
path is 1 inch, the inductance will be approximately 25nH.
Schottky diode capacitance of 100pF will create a reso-
nance at 100MHz. This ringing is not harmful to the
LT1376 and can normally be ignored.
Overshoot or ringing following switch fall time is created
by switch capacitance rather than diode capacitance. This
ringing per se is not harmful, but the overshoot can cause
problems if the amplitude becomes too high. The negative
voltage can forward bias parasitic junctions on the IC chip
and cause erratic switching. The LT1376 has special
circuitry inside which mitigates this problem, but negative
voltages over 1V lasting longer than 10ns should be
avoided. Note that 100MHz oscilloscopes are barely fast
enough to see the details of the falling edge overshoot in
Figure 7.
A second, much lower frequency ringing is seen during
switch off time if load current is low enough to allow the
inductor current to fall to zero during part of the switch off
time (see Figure 8). Switch and diode capacitance reso-
nate with the inductor to form damped ringing at 1MHz to
10 MHz. Again, this ringing is not harmful to the regulator
and it has not been shown to contribute significantly to
EMI. Any attempt to damp it with a resistive snubber will
degrade efficiency.
INPUT BYPASSING AND VOLTAGE RANGE
Input Bypass Capacitor
Step-down converters draw current from the input supply
in pulses. The average height of these pulses is equal to
load current, and the duty cycle is equal to V
OUT
/V
IN
. Rise
and fall time of the current is very fast. A local bypass
capacitor across the input supply is necessary to ensure
proper operation of the regulator and minimize the ripple
current fed back into the input supply. The capacitor also
forces switching current to flow in a tight local loop,
mnimzing EMI
Do not cheat on the ripple current rating of the Input
bypass capacitor, but also dont get hung up on the value
in mcrofarads The input capacitor is intended to absorb
all the switching current ripple, which can have an RMS
value as high as one half of load current. Ripple current
ratings on the capacitor must be observed to ensure
reliable operation. The actual value of the capacitor in
microfarads is not particularly important because at
500kHz, any value above 5
μ
F is essentially resistive. RMS
ripple current rating is the critical parameter. Actual RMS
current can be calculated from:
I
I
V
V
V
V
RIPPLE RMS
OUT
OUT
IN
OUT
IN
)
=
(
)
/
2
The term inside the radical has a maximum value of 0.5
when input voltage is twice output, and stays near 0.5 for
a relatively wide range of input voltages. It is common
5V/DIV
Figure 7. Switch Node Resonance
20ns/DIV
1375/76 F07
20ns/DIV
1375/76 F11
0.5
μ
s/DIV
1375/76 F08
Figure 8. Discontinuous Mode Ringing
5V/DIV
100mA/DIV
RISE AND FALL
WAVEFORMS ARE
SUPERIMPOSED
(PULSE WIDTH IS
NOT 120ns)
SWITCH NODE
VOLTAGE
INDUCTOR
CURRENT
相關(guān)PDF資料
PDF描述
LT1376IS8-5 RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
LT1375HVIS8 RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
LT1376HVIS8 RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
LT1375IN8 RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
LT1375IN8-5 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
LT1376IN8 功能描述:IC REG BUCK ADJ 1.5A 8DIP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 設(shè)計(jì)資源:Design Support Tool 標(biāo)準(zhǔn)包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細(xì)型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT
LT1376IN8#PBF 功能描述:IC REG BUCK ADJ 1.5A 8DIP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 設(shè)計(jì)資源:Design Support Tool 標(biāo)準(zhǔn)包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細(xì)型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT
LT1376IN8-5 功能描述:IC REG BUCK 5V 1.5A 8DIP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 設(shè)計(jì)資源:Design Support Tool 標(biāo)準(zhǔn)包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細(xì)型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT
LT1376IN8-5#PBF 功能描述:IC REG BUCK 5V 1.5A 8DIP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:20 系列:SIMPLE SWITCHER® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:12V 輸入電壓:4 V ~ 60 V PWM 型:電壓模式 頻率 - 開關(guān):52kHz 電流 - 輸出:1A 同步整流器:無(wú) 工作溫度:-40°C ~ 125°C 安裝類型:通孔 封裝/外殼:16-DIP（0.300"，7.62mm） 包裝:管件 供應(yīng)商設(shè)備封裝:16-DIP 其它名稱:*LM2575HVN-12LM2575HVN-12
LT1376IS 功能描述:IC REG BUCK ADJ 1.5A 16SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 設(shè)計(jì)資源:Design Support Tool 標(biāo)準(zhǔn)包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細(xì)型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT
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