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| 型号： | LT3431IFE#TR |
| 厂商： | Linear Technology |
| 文件页数： | 10/28页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 3A 16TSSOP |
| 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： | 1.2 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： | 带卷 (TR) |
| 供应商设备封装： | 16-TSSOP-EP |
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LT3431
APPLICATIO S I FOR ATIO
importance, the subsequent suggestions in Peak Induc-
tor and Fault Current and EMI will additionally help in the
selection of the inductor value.
Peak-to-peak output ripple voltage is the sum of a triwave
(created by peak-to-peak ripple current (I LP-P ) times ESR)
and a square wave (created by parasitic inductance (ESL)
and ripple current slew rate). Capacitive reactance is
assumed to be small compared to ESR or ESL.
physically larger inductor with the possibility of increased
component height and cost.
Ceramic Output Capacitor
An alternative way to further reduce output ripple voltage
is to reduce the ESR of the output capacitor by using a
ceramic capacitor. Although this reduction of ESR re-
moves a useful zero in the overall loop response, this zero
can be replaced by inserting a resistor (R C ) in series with
V RIPPLE = ( I LP - P )( ESR ) + ( ESL ) Σ
dI
dt
the V C pin and the compensation capacitor C C . (See
Ceramic Capacitors in Applications Information.)
where:
ESR = equivalent series resistance of the output
capacitor
ESL = equivalent series inductance of the output
capacitor
dI/dt = slew rate of inductor ripple current = V IN /L
Peak-to-peak ripple current (I LP-P ) through the inductor
and into the output capacitor is typically chosen to be
between 20% and 40% of the maximum load current. It is
approximated by:
Peak Inductor Current and Fault Current
To ensure that the inductor will not saturate, the peak
inductor current should be calculated knowing the maxi-
mum load current. An appropriate inductor should then
be chosen. In addition, a decision should be made whether
or not the inductor must withstand continuous fault
conditions.
If maximum load current is 1A, for instance, a 1A inductor
may not survive a continuous 4A overload condition. Dead
shorts will actually be more gentle on the inductor because
the LT3431 has frequency and current limit foldback.
V OUT )( IN OUT
I LP - P =
(
V – V
( V IN )( f )( L )
)
Peak inductor and switch current can be significantly
higher than output current, especially with smaller induc-
tors and lighter loads, so don’t omit this step. Powdered
iron cores are forgiving because they saturate softly,
( 5 ) ( 12 ? 5 )
( 12 ) ( )( ) 3
I P- P = = 0 . 58 A
? 6
Σ
= = 10 6 ? 1 . 2
)( ) (
)( ) ( 1 . 2 )
(
( I LP - P ) ( V OUT )( V IN – V OUT )
( )( )( )( )
2 V IN f L
Example: with V IN = 12V, V OUT = 5V, L = 10μH, ESR =
0.080 ? and ESL = 10nH, output ripple voltage can be
approximated as follows:
10 ? 10 500 ? 10
dI 12
dt 10 ? 10 ? 6
V RIPPLE = 0 . 58 A 0 . 08 + 10 ? 10 ? 9 10 6
= 0 . 046 + 0 . 012 = 58 mV P- P
To reduce output ripple voltage further requires an in-
crease in the inductor value with the trade-off being a
whereas ferrite cores saturate abruptly. Other core mate-
rials fall somewhere in between. The following formula
assumes continuous mode of operation, but errs only
slightly on the high side for discontinuous mode, so it can
be used for all conditions.
I PEAK = I OUT + = I OUT +
2
EMI
Decide if the design can tolerate an “open” core geometry
like a rod or barrel, which have high magnetic field
radiation, or whether it needs a closed core like a toroid to
prevent EMI problems. This is a tough decision because
the rods or barrels are temptingly cheap and small and
sn3431 3431fs
10
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| LT3433EFE | 功能描述:IC REG BUCK BST ADJ 0.5A 16TSSOP RoHS:否 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 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:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3433EFE#PBF | 功能描述:IC REG BUCK BST 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 |
| LT3433EFE#TR | 功能描述:IC REG BUCK BST ADJ 0.5A 16TSSOP RoHS:否 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 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:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
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