参数资料
| 型号： | LT1072CSW#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 8/16页 |
| 文件大小： | 0K |
| 描述： | IC REG MULTI CONFIG ADJ 16SOIC |
| 标准包装： | 47 |
| 类型： | 降压（降压），升压（升压），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 ~ 60 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 40kHz |
| 电流 - 输出： | 1.25A |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 100°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SOIC（0.295"，7.50mm 宽） |
| 包装： | 管件 |
| 供应商设备封装： | 16-SOIC |
LT1072
LT1072 OPERATIO
( (
(
(
KT (t S )(f S ) I C + V C
? V OS =
= 26mV at 25 ° C
rough guide to calculate LT1072 power dissipation. For
more details, the reader is referred to Application Note 19
(AN19), “Efficiency Calculations” section.
Average supply current (including driver current) is:
I IN ≈ 6mA + I SW (0.004 + DC/40)
I SW = switch current
DC = switch duty cycle
Switch power dissipation is given by:
P SW = (I SW ) 2 ? R SW ? DC
R SW = LT1072 switch “on” resistance (1 ? maximum)
Total power dissipation is the sum of supply current times
input voltage plus switch power:
P TOT = (l lN )(V IN ) + P SW
In a typical example, using a boost converter to generate
12V @ 0.12A from a 5V input, duty cycle is approximately
60%, and switch current is about 0.65A, yielding:
l lN = 6mA + 0.65(0.004 + DC/40) = 18mA
P SW = (0.65) 2 ? 1 ? ? (0.6) = 0.25W
P TOT = (5V)(0.018A) + 0.25 = 0.34W
Temperature rise in a plastic miniDIP would be 130 ° C/W
times 0.34W, or approximately 44 ° C. The maximum
ambient temperature would be limited to 100 ° C
(commercial temperature limit) minus 44 ° C, or 56 ° C.
In most applications, full load current is used to calculate
die temperature. However, if overload conditions must
also be accounted for, four approaches are possible. First,
if loss of regulated output is acceptable under overload
conditions, the internal thermal limit of the LT1072 will
protect the die in most applications by shutting off switch
current. Thermal limit is not a tested parameter, however,
and should be considered only for non-critical applications
with temporary overloads. A second approach is to use the
larger TO-220 (T) or TO-3 (K) package which, even without
a heat sink, may limit die temperatures to safe levels under
overload conditions. In critical situations, heat sinking
of these packages is required; especially if overload
conditions must be tolerated for extended periods of time.
The third approach for lower current applications is to
leave the second switch emitter open. This increases
switch “on” resistance by 2:1, but reduces switch current
limit by 2:1 also, resulting in a net 2:1 reduction in I 2 R
switch dissipation under current limit conditions.
The fourth approach is to clamp the V C pin to a voltage less
than its internal clamp level of 2V. The LT1072 switch
current limit is zero at approximately 1V on the V C pin and
2A at 2V on the V C pin. Peak switch current can be
externally clamped between these two levels with a diode.
See AN-19 for details.
LT1072 Synchronizing
The LT1072 can be externally synchronized in the frequency
range of 48kHz to 70kHz. This is accomplished as shown
in the accompanying figures. Synchronizing occurs when
the V C pin is pulled to ground with an external transistor.
To avoid disturbing the DC characteristics of the internal
error amplifier, the width of the synchronizing pulse
should be under 1 μ s. C2 sets the pulse width at ≈ 0.35 μ s.
The effect of a synchronizing pulse on the LT1072
amplifier offset can be calculated from:
q R3
I C
K T
q
t S = pulse width
f S = pulse frequency
I C = LT1072 V C source current ( ≈ 200 μ A)
V C = LT1072 operating V C voltage (1V to 2V)
R3 = resistor used to set mid-frequency “zero” in LT1072
frequency compensation network.
With t S = 0.35 μ s, f S = 50kHz, V C = 1.5V, and R3 = 2K ? ,
offset voltage shift is ≈ 2.2mV. This is not particularly
bothersome, but note that high offsets could result
if R3 were reduced to a much lower value. Also, the
synchronizing transistor must sink higher currents with
low values of R3, so larger drives may have to be used. The
transistor must be capable of pulling the V C pin to within
200mV of ground to ensure synchronizing.
1072fc
8
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| LT1072CT | 功能描述:IC REG MULTI CONFIG ADJ TO220 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:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LT1072CT#06 | 功能描述:IC REG MULTI CONFIG ADJ TO220 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:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
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