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| 型号： | LT3431IFE |
| 厂商： | Linear Technology |
| 文件页数： | 25/28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
POSITIVE-TO-NEGATIVE CONVERTER
The circuit in Figure 15 is a positive-to-negative topology
using a grounded inductor. It differs from the standard
approach in the way the IC chip derives its feedback signal
because the LT3431 accepts only positive feedback sig-
nals. The ground pin must be tied to the regulated negative
output. A resistor divider to the FB pin then provides the
proper feedback voltage for the chip.
The following equation can be used to calculate maximum
load current for the positive-to-negative converter:
Inductor Value
The criteria for choosing the inductor is typically based on
ensuring that peak switch current rating is not exceeded.
This gives the lowest value of inductance that can be used,
but in some cases (lower output load currents) it may give
a value that creates unnecessarily high output ripple
voltage.
The difficulty in calculating the minimum inductor size
needed is that you must first decide whether the switcher
will be in continuous or discontinuous mode at the critical
? ( V OUT IN – 0 . 15 )
I MAX
=
?
? I P –
?
( V IN )( V OUT ) ?
2 ( V OUT + V IN )( f )( L ) ?
( V OUT + V IN – 0 . 15 )( V OUT + V F )
)( V
point where switch current reaches 3A. The first step is to
use the following formula to calculate the load current
above which the switcher must use continuous mode. If
your load current is less than this, use the discontinuous
mode formula to calculate minimum inductor needed. If
( V IN ) ( I P ) 2
I P = Maximum rated switch current
V IN = Minimum input voltage
V OUT = Output voltage
V F = Catch diode forward voltage
0.15 = Switch voltage drop at 3A
Example: with V IN(MIN) = 5.5V, V OUT = 12V, L = 3.9 μ H,
V F = 0.52V, I P = 3A: I MAX = 0.6A.
load current is higher, use the continuous mode formula.
Output current where continuous mode is needed:
2
I CONT >
4 ( V IN + V OUT )( V IN + V OUT + V F )
Minimum inductor discontinuous mode:
D2 ?
MMSD914TI
L MIN =
2(V OUT )(I OUT )
( f )( I P ) 2
INPUT
BOOST
C2
0.22 μ F
L1*
3.9 μ H
Minimum inductor continuous mode:
2 ( f )( V IN OUT P OUT ? 1 + OUT F ? ?
? ?
12V
C3
2.2 μ F
25V
CER
V IN
LT3431
GND
SW
FB
V C
C C
D1
30BQ060
R1
36.5k
+
R2
C1
100 μ F
16V TANT
L MIN =
+ V ) ? I – I
( V IN )( V OUT )
? ? ( V + V ) ? ?
?
? V IN ? ?
C F
R C
4.12k
OUTPUT**
For a 12V to –12V converter using the LT3431 with peak
* INCREASE L1 FOR HIGHER CURRENT APPLICATIONS.
SEE APPLICATIONS INFORMATION
–12V, 0.5A
3431 F15
switch current of 3A and a catch diode of 0.52V:
( 12 ) ( 3 ) 2
** MAXIMUM LOAD CURRENT DEPENDS ON MINIMUM INPUT VOLTAGE
AND INDUCTOR SIZE. SEE APPLICATIONS INFORMATION
Figure 15. Positive-to-Negative Converter
I CONT =
2
4 ( 12 + 12 )( 12 + 12 + 0 . 52 )
= 0 . 742 A
sn3431 3431fs
25
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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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