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| 型号： | LT3431IFE |
| 厂商： | Linear Technology |
| 文件页数： | 13/28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： | 1.2 V ~ 48 V |
| 输入电压： | 5.5 V ~ 60 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 500kHz |
| 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 |
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LT3431
APPLICATIO S I FOR ATIO
f ? t ON ≤
time involved in both the current comparator and turnoff
of the output switch. These result in a minimum on time
t ON(MIN) . When combined with the large ratio of V IN to
(V F + I ? R), the diode forward voltage plus inductor I ? R
voltage drop, the potential exists for a loss of control.
Expressed mathematically the requirement to maintain
control is:
V F + I ? R
V IN
where:
f = switching frequency
t ON = switch minimum on time
V F = diode forward voltage
V IN = Input voltage
I ? R = inductor I ? R voltage drop
If this condition is not observed, the current will not be
limited at I PK , but will cycle-by-cycle ratchet up to some
higher value. Using the nominal LT3431 clock frequency
of 500KHz, a V IN of 12V and a (V F + I ? R) of say 0.6V, the
maximum t ON to maintain control would be approximately
100ns, an unacceptably short time.
The solution to this dilemma is to slow down the oscilla-
tor when the FB pin voltage is abnormally low thereby
indicating some sort of short-circuit condition. Oscillator
frequency is unaffected until FB voltage drops to about 2/3
of its normal value. Below this point the oscillator fre-
quency decreases roughly linearly down to a limit of about
100kHz. This lower oscillator frequency during short-
circuit conditions can then maintain control with the
effective minimum on time. Even with frequency foldback,
however, the LT3431 will not survive a permanent output
short at the absolute maximum voltage rating of V IN = 60V;
this is defined solely by internal semiconductor junction
breakdown effects.
For the maximum input voltage allowed during an output
short to ground, the previous equation defining minimum
maximum allowable input voltage during an output short
to ground is typically:
V IN = (0.52V + 0.068V)/(100kHz ? 275ns)
V IN(MAX) = 21V
Increasing the DCR of the inductor will increase the
maximum V IN allowed during an output short to ground
but will also drop overall efficiency during normal opera-
tion.
It is recommended that for [V IN /(V OUT + V F )] ratios > 4, a
soft-start circuit should be used to control the output
capacitor charge rate during start-up or during recovery
from an output short circuit, thereby adding additional
control over peak inductor current. See Buck Converter
with Adjustable Soft-Start later in this data sheet.
OUTPUT CAPACITOR
The LT3431 will operate with either ceramic or tantalum
output capacitors. The output capacitor is normally cho-
sen by its effective series resistance (ESR), because this
is what determines output ripple voltage. The ESR range
for typical LT3431 applications using a tantalum output
capacitor 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 criti-
cal, 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 will be terrible. Table 3 shows
some typical solid tantalum surface mount capacitors.
Table 3. Surface Mount Solid Tantalum Capacitor ESR
and Ripple Current
ESR (Max., ? ) Ripple Current (A)
E Case Size
on-time can be used. Assuming V F (D1 catch diode) =
0.52V at 2.5A (short-circuit current is folded back to
typical switch current limit ? 0.5), I (inductor) ? DCR = 2.5A
? 0.027 = 0.068V (L = UP2B-100), typical f = 100kHz
(folded back) and typical minimum on-time = 275ns, the
AVX TPS, Sprague 593D
D Case Size
AVX TPS, Sprague 593D
C Case Size
AVX TPS
0.1 to 0.3
0.1 to 0.3
0.2 (typ)
0.7 to 1.1
0.7 to 1.1
0.5 (typ)
sn3431 3431fs
13
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相关代理商/技术参数 |
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| LT3431IFE#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:- 产品培训模块:MIC23xxx HyperLight Load™ Regulators 标准包装:5,000 系列:HyperLight Load® 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.8V 输入电压:2.7 V ~ 5.5 V PWM 型:混合物 频率 - 开关:4MHz 电流 - 输出:2A 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘，8-MLF? 包装:带卷 (TR) 供应商设备封装:8-MLF?（2x2） 产品目录页面:1094 (CN2011-ZH PDF) 其它名称:576-3303-2 |
| LT3431IFE#PBF | 制造商:Linear Technology 功能描述:IC STEP-DOWN REGULATOR 16-TSSOP 制造商:Linear Technology 功能描述:IC, STEP-DOWN REGULATOR, 16-TSSOP |
| LT3431IFE#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 |
| LT3431IFE#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 |
| LT3433 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Voltage Step-Up/Step-Down DC/DC Converter |
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