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| 型号： | LT3431IFE |
| 厂商： | Linear Technology |
| 文件页数： | 12/28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
To calculate actual peak switch current with a given set of
conditions, use:
Example: For V IN = 12V, V OUT = 5V, V F = 0.52V, f = 500kHz
and L = 2.2 μ H.
I SW ( ) = I OUT +
(
2 ( )( )( V IN )
3 2 ? ( 500 ? 10 3 )( 4 . 7 ? 10 – 6 )( 12 )
2 ( 5 + 0 . 52 )( 12 – 5 – 0 . 52 )
PEAK
= I OUT +
I L P -P
2
( V OUT + V F ) V IN ? V OUT – V F
L f
)
I OUT(MAX)
Discontinuous =
Mode
I OUT(MAX) = 1.66A
Discontinuous Mode
What has been shown here is that if high inductor ripple
Reduced Inductor Value and Discontinuous Mode
If the smallest inductor value is of most importance to a
converter design, in order to reduce inductor size/cost,
discontinuous mode may yield the smallest inductor solu-
tion. The maximum output load current in discontinuous
mode, however, must be calculated and is defined later in
this section.
Discontinuous mode is entered when the output load
current is less than one-half of the inductor ripple
current (I LP-P ). In this mode, inductor current falls to
zero before the next switch turn on (see Figure 8). Buck
converters will be in discontinuous mode for output
load current given by:
current and discontinuous mode operation can be toler-
ated, small inductor values can be used. If a higher output
load current is required, the inductor value must be
increased. If I OUT(MAX) no longer meets the discontinuous
mode criteria, use the I OUT(MAX) equation for continuous
mode; the LT3431 is designed to operate well in both
modes of operation, allowing a large range of inductor
values to be used.
Short-Circuit Considerations
For a ground short-circuit fault on the regulated output,
the maximum input voltage for the LT3431 is typically
limited to 21V. If a greater input voltage is required,
increasing the resistance in series with the inductor may
suffice (see short-circuit calculations at the end of this
I OUT
Discontinuous Mode
<
( V OUT + V F )( V IN – V OUT – V F )
( 2 )( V IN )( f )( L )
section). Alternatively, the LT3430 can be used since it is
identical to the LT3431 but runs at a lower frequency of
200kHz, allowing higher sustained input voltage capability
=
( 2 )( I LP-P )
( )
The inductor value in a buck converter is usually chosen
large enough to keep inductor ripple current (I LP-P ) low;
this is done to minimize output ripple voltage and maxi-
mize output load current. In the case of large inductor
values, as seen in the equation above, discontinuous
mode will be associated with “light loads.”
When choosing small inductor values, however, discon-
tinuous mode will occur at much higher output load
currents. The limit to the smallest inductor value that can
be chosen is set by the LT3431 peak switch current (I P )
and the maximum output load current required, given by:
2
I OUT(MAX) I P
Discontinuous Mode
2
I P f ? L ? V IN
=
2 ( V OUT + V F )( V IN – V OUT – V F )
during output short-circuit.
The LT3431 is a current mode controller. It uses the V C
node voltage as an input to a current comparator which
turns off the output switch on a cycle-by-cycle basis as
peak current is reached. The internal clamp on the V C
node, nominally 2V, then acts as an output switch peak
current limit. This action becomes the switch current limit
specification. The maximum available output power is
then determined by the switch current limit.
A potential controllability problem could occur under
short-circuit conditions. If the power supply output is
short circuited, the feedback amplifier responds to the low
output voltage by raising the control voltage, V C , to its
peak current limit value. Ideally, the output switch would
be turned on, and then turned off as its current exceeded
the value indicated by V C . However, there is finite response
sn3431 3431fs
12
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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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