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| 型号： | LT1959CS8 |
| 厂商： | Linear Technology |
| 文件页数： | 9/24页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 4.5A 8SOIC |
| 标准包装： | 100 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.21 V ~ 38 V |
| 输入电压： | 4.3 V ~ 15 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 500kHz |
| 电流 - 输出： | 4.5A |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 供应商设备封装： | 8-SOIC |
LT1959
APPLICATIO N S I N FOR M ATIO N
I OUT(MAX) = ( V OUT ) ( V IN ? V OUT )
2 ( )( )( )
Continuous Mode L f V
The internal circuitry which forces reduced switching
frequency also causes current to flow out of the feedback
pin when output voltage is low. The equivalent circuitry is
shown in Figure 2. Q1 is completely off during normal
operation. If the FB pin falls below 0.7V, Q1 begins to
conduct current and reduces frequency at the rate of
approximately 2kHz/ μ A. To ensure adequate frequency
foldback (under worst-case short-circuit conditions), the
external divider Thevinin resistance must be low enough
to pull 150 μ A out of the FB pin with 0.3V on the pin (R DIV
≤ 2k). The net result is that reductions in frequency and
finite inductor size, maximum load current is reduced by
one-half peak-to-peak inductor current. The following
formula assumes continuous mode operation, implying
that the term on the right is less than one-half of I P .
I P ?
IN
For the conditions above and L = 3.3 μ H,
2 ? 3 . 3 ? 10 ? ?? 500 ? 10 ? ()
currentlimitareaffectedbyoutputvoltagedividerimped-
ance. Although divider impedance is not critical, caution
should be used if resistors are increased beyond the
suggested values and short-circuit conditions will occur
I OUT ( MAX ) = 4 . 3 ?
( 5 ) ( 8 ? 5 )
? 6 3
2 ? 3 . 3 ? 10 ? ?? 500 ? 10 ? ( 15 )
V OUT ( V IN ? V OUT )
2 ( )( )( )
with high input voltage. High frequency pickup will
increase and the protection accorded by frequency and
current foldback will decrease.
MAXIMUM OUTPUT LOAD CURRENT
Maximum load current for a buck converter is limited by
the maximum switch current rating (I P ) of the LT1959.
This current rating is 4.5A up to 50% duty cycle (DC),
decreasing to 3.7A at 80% duty cycle. This is shown
graphically in Typical Performance Characteristics and as
shown in the formula below:
I P = 4.5A for DC ≤ 50%
I P = 3.21 + 5.95(DC) – 6.75(DC) 2 for 50% < DC < 90%
DC = Duty cycle = V OUT /V IN
Example: with V OUT = 5V, V IN = 8V; DC = 5/8 = 0.625, and;
I SW(MAX) = 3.21 + 5.95(0.625) – 6.75(0.625) 2 = 4.3A
Current rating decreases with duty cycle because the
LT1959 has internal slope compensation to prevent cur-
rent mode subharmonic switching. For more details, read
Application Note 19. The LT1959 is a little unusual in this
regard because it has nonlinear slope compensation which
gives better compensation with less reduction in current
limit.
= 4 . 3 ? 0 . 57 = 3 . 73 A
At V IN = 15V, duty cycle is 33%, so I P is just equal to a fixed
4.5A, and I OUT(MAX) is equal to:
4 . 5 ? ( 5 ) ( 15 ? 5 )
? 6 3
= 4 . 5 ? 1 . 01 = 3 . 49 A
Note that there is less load current available at the higher
input voltage because inductor ripple current increases.
This is not always the case. Certain combinations of
inductor value and input voltage range may yield lower
available load current at the lowest input voltage due to
reduced peak switch current at high duty cycles. If load
current is close to the maximum available, please check
maximum available current at both input voltage ex-
tremes. To calculate actual peak switch current with a
given set of conditions, use:
I SW ( PEAK ) = I OUT + L f V
IN
Maximum load current would be equal to maximum
switch current for an infinitely large inductor, but with
9
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1959CS8#PBF | 功能描述:IC REG BUCK ADJ 4.5A 8SOIC 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 |
| LT1959CS8#TR | 功能描述:IC REG BUCK ADJ 4.5A 8SOIC 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 |
| LT1959CS8#TRPBF | 功能描述:IC REG BUCK ADJ 4.5A 8SOIC 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 |
| LT1959I | 制造商:LINER 制造商全称:Linear Technology 功能描述:4.5A, 500kHz Step-Down Switching Regulator |
| LT1959IR | 功能描述:IC REG BUCK ADJ 4.5A D2PAK 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 |
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