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| 型号： | LT3434IFE |
| 厂商： | Linear Technology |
| 文件页数： | 11/24页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 3A 16TSSOP |
| 标准包装： | 95 |
| 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： | 3A |
| 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： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 16-TSSOP-EP |
LT3434
APPLICATIO S I FOR ATIO
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 volt-
age by 2:1 for high surge applications.
OUTPUT CAPACITOR
Unlike the input capacitor RMS, ripple current in the
output capacitor is normally low enough that ripple cur-
rent rating is not an issue. The current waveform is
triangular with a typical value of 200mA RMS . The formula
to calculate this is:
Output capacitor ripple current (RMS)
= P-P
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
I RIPPLE ( RMS ) =
0. 29 ( V OUT )( V IN – V OUT )
( L )( f )( V IN )
I
12
physically smaller capacitors have higher ESR. The ESR
range for typical LT3434 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.
Table 2. Surface Mount Solid Tantalum Capacitor ESR
and Ripple Current
E CASE SIZE ESR MAX ( ? ) RIPPLE CURRENT (A)
AVX TPS 0.1 to 0.3 0.7 to 1.1
D CASE SIZE
AVX TPS 0.1 to 0.3 0.7 to 1.1
C CASE SIZE
AVX TPS 0.2 0.5
Many engineers have heard that solid tantalum capacitors
are prone to failure if they undergo high surge currents.
This is historically true and type TPS capacitors are
specially tested for surge capability but surge ruggedness
is not a critical issue with the output capacitor. Solid
tantalum capacitors fail during very high turn-on surges
which do not occur at the output of regulators. High
CERAMIC CAPACITORS
Higher value, lower cost ceramic capacitors are now
becoming available. They are generally chosen for their
good high frequency operation, small size and very low
ESR (effective series resistance). Low ESR reduces output
ripple voltage but also removes a useful zero in the loop
frequency response, common to tantalum capacitors. To
compensate for this a resistor R C can be placed in series
with the V C compensation capacitor C C (Figure 10). Care
must be taken however since this resistor sets the high
frequency gain of the error amplifier including the gain at
the switching frequency. If the gain of the error amplifier
is high enough at the switching frequency output ripple
voltage (although smaller for a ceramic output capacitor)
may still affect the proper operation of the regulator. A
filter capacitor C F in parallel with the R C /C C network, along
with a small feedforward capacitor C FB , is suggested to
control possible ripple at the V C pin. The LT3434 can be
stabilized using a 100 μ F ceramic output capacitor and V C
component values of C C = 4700pF, R C = 10k, C F = 470pF
and C FB = 27pF.
OUTPUT RIPPLE VOLTAGE
Figure 3 shows a typical output ripple voltage waveform
for the LT3434. Ripple voltage is determined by the
impedance of the output capacitor and ripple current
through the inductor. Peak-to-peak ripple current through
the inductor into the output capacitor is:
discharge surges, such as when the regulator output is
dead shorted, do not harm the capacitors.
I P-P =
V OUT ( V IN – V OUT )
( V IN )( L )( f )
3434fb
11
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相关代理商/技术参数 |
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|---|---|
| LT3434IFE#PBF | 功能描述:IC REG BUCK ADJ 3A 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 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:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT3434IFE#PBF | 制造商:Linear Technology 功能描述:IC, STEP-DOWN REGULATOR, 16-TSSOP |
| LT3434IFE#TR | 功能描述:IC REG BUCK ADJ 3A 16TSSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 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:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT3434IFE#TRPBF | 功能描述:IC REG BUCK ADJ 3A 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 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:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT3434IFEPBF | 制造商:Linear Technology 功能描述:DC-DC Converter Step-Down 60V TSSOP16EP |
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