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参数资料
| 型号： | LT1108CS8-5#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 5/12页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK BST INV 5V .4A 8SOIC |
| 标准包装： | 2,500 |
| 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： | 5V |
| 输入电压： | 2 V ~ 30 V |
| 频率 - 开关： | 19kHz |
| 电流 - 输出： | 400mA |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 70°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 |
LT1108
1 OPER ATI
The LT1108 is a gated oscillator switcher. This type
architecture has very low supply current because the
switch is cycled when the feedback pin voltage drops
below the reference voltage. Circuit operation can best be
understood by referring to the LT1108 block diagram.
Comparator A1 compares the feedback (FB) pin voltage
with the 1.245V reference signal. When FB drops below
1.245V, A1 switches on the 19kHz oscillator. The driver
amplifier boosts the signal level to drive the output NPN
power switch. The switch cycling action raises the output
voltage and FB pin voltage. When the FB voltage is suffi-
cient to trip A1, the oscillator is gated off. A small amount
of hysteresis built into A1 ensures loop stability without
external frequency compensation. When the comparator
output is low, the oscillator and all high current circuitry
is turned off, lowering device quiescent current to just
110 μ A.
The oscillator is set internally for 36 μ s ON-time and 17 μ s
OFF-time, allowing continuous mode operation in many
cases such as 2V to 5V converters. Continuous mode
greatly increases available output power.
Gain block A2 can serve as a low battery detector. The
BLOCK D I AGRA S
LT1108
SET
negative input of A2 is the 1.245V reference. A resistor
divider from V IN to GND, with the mid-point connected to
the SET pin provides the trip voltage in a low battery
detector application. A0 can sink 100 μ A (use a 47k resis-
tor pull-up to 5V).
A resistor connected between the I LIM pin and V IN sets
maximum switch current. When the switch current ex-
ceeds the set value, the switch cycle is prematurely
terminated. If current limit is not used, I LIM should be tied
directly to V IN . Propagation delay through the current-
limit circuitry is approximately 2 μ s.
In step-up mode the switch emitter (SW2) is connected to
ground and the switch collector (SW1) drives the induc-
tor; in step-down mode the collector is connected to V IN
and the emitter drives the inductor.
The LT1108-5 and LT1108-12 are functionally identical to
the LT1108. The -5 and -12 versions have on-chip voltage
setting resistors for fixed 5V or 12V outputs. Pin 8 on the
fixed versions should be connected to the output. No
external resistors are needed.
LT1108-5/LT1108-12
SET
V IN
A2
GAIN BLOCK/
A0
V IN
A2
GAIN BLOCK/
A0
ERROR AMP
I LIM
SW1
ERROR AMP
I LIM
SW1
1.245V
REFERENCE
1.245V
REFERENCE
A1
OSCILLATOR
DRIVER
A1
OSCILLATOR
DRIVER
GND
FB
COMPARATOR
LT1108 ? BD
SW2
R2
COMPARATOR
LT1108-5 ? BD
SW2
GND
R1
753k
SENSE
LT1108-5: R1 = 250k
LT1108-12: R1 = 87.4k
5
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相关代理商/技术参数 |
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|---|---|
| LT1108CS8PBF | 制造商:Linear Technology 功能描述:DC/DC Converter Adj Micropower 2-30V SO8 |
| LT1109 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower Low Cost DC/DC Converter Adjustable and Fixed 5V, 12V |
| LT1109-12 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower Low Cost DC/DC Converter Adjustable and Fixed 5V, 12V |
| LT1109-5 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower Low Cost DC/DC Converter Adjustable and Fixed 5V, 12V |
| LT1109A | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower DC/DC Converter Flash Memory VPP Generator Adjustable and Fixed 5V, 12V |
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