參數(shù)資料
型號(hào)： LT3437EDD
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： 0.9 A SWITCHING REGULATOR, 240 kHz SWITCHING FREQ-MAX, PDSO10
封裝： 3 X 3 MM, 0.75 MM HEIGHT, PLASTIC, MO-229WEED-2, DFN-10
文件頁(yè)數(shù)： 10/24頁(yè)
文件大?。?/td> 523K
代理商： LT3437EDD
LT3437
10
3437f
cause the input voltage to swing above the DC level of input
power source and it may exceed the maximum voltage
rating of the input capacitor and LT3437. All input voltage
transient sequences should be observed at the V
IN
pin of
the LT3437 to ensure that absolute maximum voltage
ratings are not violated.
The easiest way to suppress input voltage transients is to
add a small aluminum electrolytic capacitor in parallel with
the low ESR input capacitor. The selected capacitor needs
to have the right amount of ESR to critically damp the
resonant circuit formed by the input lead inductance and
the input capacitor. The typical values of ESR will fall in the
range of 0.5
to 2
and capacitance will fall in the range
of 5
μ
F to 50
μ
F.
If tantalum capacitors are used, values in the 22
μ
F to
470
μ
F range are generally needed to minimize ESR and
meet ripple current and surge ratings. Care should be
taken to ensure the ripple and surge ratings are not
exceeded. The AVX TPS and Kemet T495 series are surge
rated. AVX recommends derating capacitor operating
voltage by 2:1 for high surge applications.
OUTPUT CAPACITOR
The output capacitor is normally chosen by its effective
series resistance (ESR) because this is what determines
output ripple voltage. To get low ESR takes volume, so
physically smaller capacitors have higher ESR. The ESR
range for typical LT3437 applications is 0.05
to 0.2
. A
typical output capacitor is an AVX type TPS, 100
μ
F at 10V,
with a guaranteed ESR less than 0.1
. This is a “D” size
surface mount solid tantalum capacitor. TPS capacitors
are specially constructed and tested for low ESR, so they
give the lowest ESR for a given volume. The value in
microfarads is not particularly critical, and values from
22
μ
F to greater than 500
μ
F work well, but you cannot
cheat Mother Nature on ESR. If you find a tiny 22
μ
F solid
tantalum capacitor, it will have high ESR and output ripple
voltage could be unacceptable. Table 2 shows some
typical solid tantalum surface mount capacitors.
function reduces input current surge by regulating switch
current via the V
C
pin to maintain a constant voltage ramp
rate (dV/dt) at the output. A capacitor (C1 in Figure 2) from
the C
SS
pin to the output determines the maximum output
dV/dt. When the feedback voltage is below 0.4V, the V
C
pin
will rise, resulting in an increase in switch current and
output voltage. If the dV/dt of the output causes the current
through the C
SS
capacitor to exceed I
CSS
, the V
C
voltage is
reduced resulting in a constant dV/dt at the output. As the
feedback voltage increases, I
CSS
increases, resulting in an
increased dV/dt until the soft-start function is defeated
with 0.9V present at the FB pin. The soft-start function
does not affect operation during normal load conditions.
However, if a momentary short (brown out condition) is
present at the output which causes the FB voltage to drop
below 0.9V, the soft-start circuitry will become active.
INPUT CAPACITOR
Step-down regulators draw current from the input supply
in pulses. The rise and fall times of these pulses are very
fast. The input capacitor is required to reduce the voltage
ripple this causes at the input of LT3437 and force the
switching current into a tight local loop, thereby minimiz-
ing EMI. The RMS ripple current can be calculated from:
I
I
V
V
V
V
RIPPLE RMS
OUT
IN
OUT
IN
OUT
(
)
–
=
(
)
Ceramic capacitors are ideal for input bypassing. At 200kHz
switching frequency input capacitor values in the range of
2.2
μ
F to 10
μ
F are suitable for most applications. If opera-
tion is required close to the minimum input required by the
LT3437, a larger value may be required. This is to prevent
excessive ripple causing dips below the minimum operat-
ing voltage resulting in erratic operation.
Input voltage transients caused by input voltage steps, or
by hot plugging the LT3437 to a pre-powered source such
as a wall adapter, can exceed maximum V
IN
ratings. The
sudden application of input voltage will cause a large
surge of current in the input leads that will store energy in
the parasitic inductance of the leads. This energy will
APPLICATIOU
W
U
U
相關(guān)PDF資料
PDF描述
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LT3437EDD#PBF 功能描述:IC REG BUCK ADJ 0.5A 10DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)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(kāi)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
LT3437EDD#TRPBF 功能描述:IC REG BUCK ADJ 0.5A 10DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開(kāi)關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無(wú) 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC
LT3437EFE 制造商:Linear Technology 功能描述:Conv DC-DC Single Step Down 3.3V to 60V 16-Pin TSSOP EP
LT3437EFE#PBF 功能描述:IC REG BUCK ADJ 0.5A 16TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:250 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V 輸入電壓:2.05 V ~ 6 V PWM 型:電壓模式 頻率 - 開(kāi)關(guān):2MHz 電流 - 輸出:500mA 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:6-UFDFN 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:6-SON（1.45x1） 產(chǎn)品目錄頁(yè)面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2
LT3437EFE#TR 制造商:Linear Technology 功能描述:Conv DC-DC Single Step Down 3.3V to 60V 16-Pin TSSOP EP T/R
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