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| 型号： | LT3437EDD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 12/28页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.5A 10DFN |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.25 V ~ 54 V |
| 输入电压： | 3.3 V ~ 60 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 200kHz |
| 电流 - 输出： | 500mA |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-DFN（3x3） |
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LT3437
APPLICATIO S I FOR ATIO
high input current surge during start-up. The soft-start
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 minimizing EMI. The RMS ripple current can be
calculated from:
surge of current in the input leads that will store energy in
the parasitic inductance of the leads. This energy will
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
V OUT ( IN OUT
I RIPPLE ( RMS ) =
I OUT
V IN
V – V
)
The output capacitor is normally chosen by its effective
series resistance (ESR) because this is what deter-
mines output ripple voltage. To get low ESR takes
volume, so physically smaller capacitors have higher
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
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 con-
structed 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
3437fc
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相关代理商/技术参数 |
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| 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 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称: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 |
| LT3437EFE#TRPBF | 功能描述:IC REG BUCK ADJ 0.5A 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LT3437EFEPBF | 制造商:Linear Technology 功能描述:Sw. Regulator 500mA 200kHz 60V TSSOP16EP |
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