参数资料
型号: LT1172MJ8#PBF
厂商: Linear Technology
文件页数: 5/24页
文件大小: 0K
描述: IC REG MULTI CONFIG ADJ 8CERDIP
标准包装: 50
类型: 降压(降压),升压(升压),反相,Cuk,回扫,正向转换器
输出类型: 可调式
输出数: 1
输出电压: 1.25 V ~ 40 V
输入电压: 3 V ~ 40 V
PWM 型: 电流模式
频率 - 开关: 100kHz
电流 - 输出: 1.25A
同步整流器:
工作温度: -55°C ~ 125°C
安装类型: 通孔
封装/外壳: 8-CDIP(0.300",7.62mm)
包装: 管件
供应商设备封装: 8-CERDIP
LT1170/LT1171/LT1172
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T A = 25°C. V IN = 15V, V C = 0.5V, V FB = V REF , output pin open, unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
DC MAX
Maximum Switch Duty Cycle
Shutdown Mode
3V ≤ V IN ≤ V MAX
l
85
92
100
97
250
%
μA
Supply Current
V C = 0.05V
Shutdown Mode
Threshold Voltage
3V ≤ V IN ≤ V MAX
l
100
50
150
250
300
mV
mV
Flyback Sense Delay Time (Note 5)
1.5
μs
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: Minimum effective switch “on” time for the LT1170/LT1171/
LT1172 (in current limit only) is ≈ 0.6μs. This limits the maximum safe
input voltage during an output shorted condition. Buck mode and inverting
mode input voltage during an output shorted condition is limited to:
V IN (max, output shorted) = 15V + ( R ) ( I L ) + Vf
buck and inverting mode ( t ) ( f )
R = Inductor DC resistance
I L = 10A for LT1170, 5A for LT1171, and 2.5A for LT1172
Transformer designs will tolerate much higher input voltages because
leakage inductance limits rate of rise of current in the switch. These
designs must be evaluated individually to assure that current limit is well
controlled up to maximum input voltage.
Boost mode designs are never protected against output shorts because
the external catch diode and inductor connect input to output.
Note 3: Measured with V C in hi clamp, V FB = 0.8V. I SW = 4A for LT1170,
2A for LT1171, and 1A for LT1172.
Note 4: For duty cycles (DC) between 50% and 80%, minimum guaranteed
switch current is given by I LIM = 3.33 (2 – DC) for the LT1170, I LIM = 1.67
(2 – DC) for the LT1171, and I LIM = 0.833 (2 – DC) for the LT1172.
Note 5: Minimum input voltage for isolated flyback mode is 7V. V MAX = 55V
for HV grade in fully isolated mode to avoid switch breakdown.
Vf = Output catch diode forward voltage at I L
t = 0.6μs, f = 100kHz switching frequency
Maximum input voltage can be increased by increasing R or Vf.
External current limiting such as that shown in AN19, Figure 39, will
provide protection up to the full supply voltage rating. C1 in Figure 39
should be reduced to 200pF.
117012fg
5
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