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| 型号： | LT1173CN8-12#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK BST INV 12V .4A 8DIP |
| 标准包装： | 50 |
| 类型： | 降压（降压），升压（升压），反相 |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 12V |
| 输入电压： | 2 V ~ 30 V |
| 频率 - 开关： | 23kHz |
| 电流 - 输出： | 400mA |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 通孔 |
| 封装/外壳： | 8-DIP（0.300"，7.62mm） |
| 包装： | 管件 |
| 供应商设备封装： | 8-PDIP |
LT1173
A PPLICATI
S I FOR ATIO
L1
D1
+V OUT
+
C2
V IN
I LIM
SW1
LT1173
+
C1
R1
2N3906
I L
AO
GND
FB
SW2
SWITCH
ON
OFF
R2
V OUT =
R2
( R1 ) 1.245V + 0.6V
LT1173 ? TA14
–V IN
Figure 8. Negative-to-Positive Converter
LT1173 ? TA13
Figure 9. No Current Limit Causes Large Inductor
Current Build-Up
Using the I LIM Pin
The LT1173 switch can be programmed to turn off at a set
switch current, a feature not found on competing devices.
I L
PROGRAMMED CURRENT LIMIT
This enables the input to vary over a wide range without
exceeding the maximum switch rating or saturating the
SWITCH
ON
OFF
( 17 )
? V
1 ? DC
inductor. Consider the case where analysis shows the
LT1173 must operate at an 800mA peak switch current
with a 2.0V input. If V IN rises to 4V, the peak switch current
will rise to 1.6A, exceeding the maximum switch current
rating. With the proper resistor selected (see the “Maxi-
mum Switch Current vs R LIM ” characteristic), the switch
current will be limited to 800mA, even if the input voltage
increases.
Another situation where the I LIM feature is useful occurs
when the device goes into continuous mode operation.
This occurs in step-up mode when
V OUT + V DIODE 1
< .
V IN SW
When the input and output voltages satisfy this relation-
ship, inductor current does not go to zero during the
LT1173 ? TA15
Figure 10. Current Limit Keeps Inductor Current Under Control
Figure 11 details current limit circuitry. Sense transistor
Q1, whose base and emitter are paralleled with power
switch Q2, is ratioed such that approximately 0.5% of Q2’s
collector current flows in Q1’s collector. This current is
passed through internal 80 ? resistor R1 and out through
the I LIM pin. The value of the external resistor connected
between I LIM and V IN sets the current limit. When suffi-
cient switch current flows to develop a V BE across R1 +
R LIM , Q3 turns on and injects current into the oscillator,
turning off the switch. Delay through this circuitry is
approximately 2 μ s. The current trip point becomes less
accurate for switch ON times less than 4 μ s. Resistor
values programming switch ON time for 2 μ s or less will
cause spurious response in the switch circuitry although
the device will still maintain output regulation.
switch OFF time. When the switch turns on again, the
current ramp starts from the non-zero current level in the
R LIM
(EXTERNAL)
I LIM
inductor just prior to switch turn on. As shown in Figure
9, the inductor current increases to a high level before the
comparator turns off the oscillator. This high current can
cause excessive output ripple and requires oversizing the
output capacitor and inductor. With the I LIM feature,
V IN
Q3
OSCILLATOR
DRIVER
R1
80 ?
(INTERNAL)
SW1
Q1
Q2
however, the switch current turns off at a programmed
level as shown in Figure 10, keeping output ripple to a
minimum.
10
SW2
LT1173 ? TA28
Figure 11. LT1173 Current Limit Circuitry
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相关代理商/技术参数 |
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| LT1173CN8-5 | 功能描述:IC REG BUCK BST INV 5V 0.4A 8DIP 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 |
| LT1173CN8-5#PBF | 功能描述:IC REG BUCK BST INV 5V 0.4A 8DIP 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 |
| LT1173CN8-5PBF | 制造商:Linear Technology 功能描述:LT1173CN8-5PBF |
| LT1173CN8PBF | 制造商:Linear Technology 功能描述:LT1173CN8PBF |
| LT1173CS8 | 功能描述:IC REG BUCK BOOST INV ADJ 8SOIC 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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