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参数资料
| 型号： | LT1170CT#PBF06 |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 11 A SWITCHING REGULATOR, 115 kHz SWITCHING FREQ-MAX, PZFM5 |
| 封装： | PLASTIC, TO-220, 5 PIN |
| 文件页数： | 19/20页 |
| 文件大小： | 278K |
| 代理商： | LT1170CT#PBF06 |
8
LT1170/LT1171/LT1172
117012ff
The LT1170/LT1171/LT1172 are current mode switchers.
This means that switch duty cycle is directly controlled by
switch current rather than by output voltage. Referring to
the block diagram, the switch is turned “on” at the start of
each oscillator cycle. It is turned “off” when switch current
reaches a predetermined level. Control of output voltage is
obtained by using the output of a voltage sensing error
amplifier to set current trip level. This technique has
several advantages. First, it has immediate response to
input voltage variations, unlike ordinary switchers which
have notoriously poor line transient response. Second, it
reduces the 90
° phase shift at midfrequencies in the
energy storage inductor. This greatly simplifies closed-
loop frequency compensation under widely varying input
voltage or output load conditions. Finally, it allows simple
pulse-by-pulse current limiting to provide maximum switch
protection under output overload or short conditions. A
low dropout internal regulator provides a 2.3V supply for
all internal circuitry on the LT1170/LT1171/LT1172. This
low dropout design allows input voltage to vary from 3V to
60V with virtually no change in device performance. A
100kHz oscillator is the basic clock for all internal timing.
It turns “on” the output switch via the logic and driver
circuitry. Special adaptive anti-sat circuitry detects onset
of saturation in the power switch and adjusts driver
current instantaneously to limit switch saturation. This
minimizes driver dissipation and provides very rapid turn-
off of the switch.
A 1.2V bandgap reference biases the positive input of the
error amplifier. The negative input is brought out for
output voltage sensing. This feedback pin has a second
function; when pulled low with an external resistor, it
programs the LT1170/LT1171/LT1172 to disconnect the
main error amplifier output and connects the output of the
flyback amplifier to the comparator input. The LT1170/
LT1171/LT1172 will then regulate the value of the flyback
pulse with respect to the supply voltage.* This flyback
pulse is directly proportional to output voltage in the
traditional transformer coupled flyback topology regula-
tor. By regulating the amplitude of the flyback pulse, the
output voltage can be regulated with no direct connection
between input and output. The output is fully floating up to
the breakdown voltage of the transformer windings. Mul-
tiple floating outputs are easily obtained with additional
OPERATIO
U
windings. A special delay network inside the LT1170/
LT1171/LT1172 ignores the leakage inductance spike at
the leading edge of the flyback pulse to improve output
regulation.
The error signal developed at the comparator input is
brought out externally. This pin (VC) has four different
functions. It is used for frequency compensation, current
limit adjustment, soft starting, and total regulator shut-
down. During normal regulator operation this pin sits at a
voltage between 0.9V (low output current) and 2.0V (high
output current). The error amplifiers are current output
(gm) types, so this voltage can be externally clamped for
adjusting current limit. Likewise, a capacitor coupled
external clamp will provide soft start. Switch duty cycle
goes to zero if the VC pin is pulled to ground through a
diode, placing the LT1170/LT1171/LT1172 in an idle mode.
Pulling the VC pin below 0.15V causes total regulator
shutdown, with only 50
A supply current for shutdown
circuitry biasing. See AN19 for full application details.
Extra Pins on the MiniDIP and Surface Mount Packages
The 8- and 16-pin versions of the LT1172 have the
emitters of the power transistor brought out separately
from the ground pin. This eliminates errors due to ground
pin voltage drops and allows the user to reduce switch
current limit 2:1 by leaving the second emitter (E2) discon-
nected. The first emitter (E1) should always be connected
to the ground pin. Note that switch “on” resistance doubles
when E2 is left open, so efficiency will suffer somewhat
when switch currents exceed 300mA. Also, note that chip
dissipation will actually
increase with E2 open during
normal load operation, even though dissipation in current
limit mode will
decrease. See “Thermal Considerations”
next.
Thermal Considerations When Using the MiniDIP and
SW Packages
The low supply current and high switch efficiency of the
LT1172 allow it to be used without a heat sink in most
applications when the TO-220 or TO-3 package is se-
lected. These packages are rated at 50
°C/W and 35°C/W
respectively.The miniDIPs, however,are rated at 100
°C/W
in ceramic (J) and 130
°C/W in plastic (N).
*See note under block diagram.
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PDF描述 |
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| 5962-9207901MPX | 1.25 A SWITCHING REGULATOR, 100 kHz SWITCHING FREQ-MAX, CDIP8 |
| LT1172HVIQ#TRPBF | 3.5 A SWITCHING REGULATOR, 115 kHz SWITCHING FREQ-MAX, PSSO5 |
| LT1171CT#FLOW-06PBF | 5.5 A SWITCHING REGULATOR, 115 kHz SWITCHING FREQ-MAX, PZFM5 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1170HV | 制造商:LINER 制造商全称:Linear Technology 功能描述:100kHz, 5A, 2.5A and 1.25A High Efficiency Switching Regulators |
| LT1170HVC | 制造商:LINER 制造商全称:Linear Technology 功能描述:100kHz, 5A, 2.5A and 1.25A High Efficiency Switching Regulators |
| LT1170HVCQ | 功能描述:IC REG MULTI CONFIG ADJ 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 |
| LT1170HVCQ#PBF | 功能描述:IC REG MULTI CONFIG ADJ 5A D2PAK 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 |
| LT1170HVCQ#PBF | 制造商:Linear Technology 功能描述:IC, SWITCHING REGULATOR, DPAK-5 |
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