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| 型号： | LT1956IFE-5#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 26/28页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 5V 1.5A 16TSSOP |
| 标准包装： | 95 |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 5V |
| 输入电压： | 5.5 V ~ 60 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 500kHz |
| 电流 - 输出： | 1.5A |
| 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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LT1956/LT1956-5
PACKAGE DESCRIPTIO
L MIN =
2 ( f )( V IN OUT ) ? I P OUT ? 1 + OUT F ? ?
+ V
?
? ?
Minimum inductor continuous mode:
( V IN )( V OUT )
? ? ( V + V ) ? ?
– I
? V IN
For a 12V to –12V converter using the LT1956 with peak
switch current of 1.5A and a catch diode of 0.63V:
The output capacitor ripple current for the positive-to-
negative converter is similar to that for a typical buck
regulator—it is a triangular waveform with peak-to-peak
value equal to the peak-to-peak triangular waveform of the
inductor. The low output ripple design in Figure 14 places
the input capacitor between V IN and the regulated negative
output. This placement of the input capacitor significantly
reduces the size required for the output capacitor (versus
( 12 ) ( 1 . 5 ) 2
I CONT >
2
4 ( 12 + 12 )( 12 + 12 + 0 . 63 )
= 0 . 370 A
placing the input capacitor between V IN and ground).
The peak-to-peak ripple current in both the inductor and
output capacitor (assuming continuous mode) is:
L MIN = = 5 . 3 μ H
I P-P =
V OUT + V F
V OUT + V IN + V F
I COUT ( RMS ) =
I OUT IN OUT +
For a load current of 0.25A, this says that discontinuous
mode can be used and the minimum inductor needed is
found from:
2 ( 12 )( 0 . 25 )
( 500 ? 10 3 )( 1 . 5 ) 2
In practice, the inductor should be increased by about
30% over the calculated minimum to handle losses and
variations in value. This suggests a minimum inductor of
7 μ H for this application.
Ripple Current in the Input and Output Capacitors
Positive-to-negative converters have high ripple current
in the input capacitor. For long capacitor lifetime, the
RMS value of this current must be less than the high
frequency ripple current rating of the capacitor. The
following formula will give an approximate value for RMS
ripple current. This formula assumes continuous mode
and large inductor value. Small inductors will give some-
what higher ripple current, especially in discontinuous
mode. The exact formulas are very complex and appear
in Application Note 44, pages 29 and 30. For our pur-
poses here I have simply added a fudge factor (ff). The
DC ? V IN
f ? L
DC = Duty Cycle =
I P-P
12
The output ripple voltage for this configuration is as low as
the typical buck regulator based predominantly on the
inductor’s triangular peak-to-peak ripple current and the
ESR of the chosen capacitor (see Output Ripple Voltage in
Applications Information).
Diode Current
Average diode current is equal to load current. Peak diode
current will be considerably higher.
Peak diode current:
Continuous Mode =
( V + V ) ( V IN )( V OUT )
V IN 2 ( L )( f )( V IN + V OUT )
value for ff is about 1.2 for higher load currents and L
≥ 15 μ H. It increases to about 2.0 for smaller inductors at
lower load currents.
Discontinuous Mode =
2 ( I OUT )( V OUT )
( L )( f )
Capacitor I RMS = ( ff )( I OUT )
ff = 1.2 to 2.0
V OUT
V IN
Keep in mind that during start-up and output overloads,
average diode current may be much higher than with
normal loads. Care should be used if diodes rated less than
1A are used, especially if continuous overload conditions
must be tolerated.
1956f
26
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1956IGN | 功能描述:IC REG BUCK ADJ 1.5A 16SSOP 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 |
| LT1956IGN#PBF | 功能描述:IC REG BUCK ADJ 1.5A 16SSOP 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 |
| LT1956IGN#PBF | 制造商:Linear Technology 功能描述:IC STEP-DOWN REGULATOR SSOP-16 |
| LT1956IGN#TR | 功能描述:IC REG BUCK ADJ 1.5A 16SSOP 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 |
| LT1956IGN#TRPBF | 功能描述:IC REG BUCK ADJ 1.5A 16SSOP 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 |
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