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參數(shù)資料
| 型號： | LTC1701 |
| 廠商： | Linear Technology Corporation |
| 元件分類： | 通用總線功能 |
| 英文描述： | Synchronous 8-Bit Up/Down Binary Counters 24-SOIC 0 to 70 |
| 中文描述： | 1MHz的降壓型DC / DC轉(zhuǎn)換器采用SOT - 23 |
| 文件頁數(shù)： | 4/12頁 |
| 文件大?。?/td> | 138K |
| 代理商： | LTC1701 |
4
LTC 1701
OPERATIOU
The LTC1701 uses a contant off-time, current mode
architecture. The operating frequency is then determined
by the off-time and the difference between V
IN
and V
OUT
.
To optimize efficiency, the LTC1701 automatically switches
between continuous and Burst Mode
operation.
The output voltage is set by an external divider returned to
the V
FB
pin. An error amplfier compares the divided output
voltage with a reference voltage of 1.25V and adjusts the
peak inductor current accordingly.
Main Control Loop
During normal operation, the internal PMOS switch is
turned on when the V
FB
voltage is below the reference
voltage. The current into the inductor and the load in-
creases until the current limit is reached. The switch turns
off and energy stored in the inductor flows through the
external Schottky diode into the load. After the constant
off-time interval, the switch turns on and the cycle repeats.
The peak inductor current is controlled by the voltage on
the I
TH
/RUN pin, which is the output of the error
amplifier.This amplifier compares the V
FB
pin to the 1.25V
reference. When the load current increases, the FB voltage
decreases slightly below the reference. This decrease
causes the error amplifier to increase the I
TH
/RUN voltage
until the average inductor current matches the new load
current.
The main control loop is shut down by pulling the I
TH
/RUN
pin to ground. When the pin is released an external resistor
is used to charge the compensation capacitor. When the
voltage at the I
TH
/RUN pin reaches 0.8V, the main control
loop is enabled and the error amplifier drives the I
TH
/RUN
pin. Soft-start can be implemented by ramping the voltage
on the I
TH
/RUN pin (see Applications Information sec-
tion).
Low Current Operation
When the load is relatively light, the LTC1701 automati-
cally switches to Burst Mode
operation in which the
internal PMOS switch operates intermittently based on
load demand. The main control loop is interrupted when
the output voltage reaches the desired regulated value.
The hysteretic voltage comparator trips when I
TH
/RUN is
below 1.5V, shutting off the switch and reducing the
power consumed. The output capacitor and the inductor
supply the power to the load until the output voltage drops
slightly and the I
TH
/RUN pin exceeds 1.5V, turning on the
switch and the main control loop which starts another
cycle.
Dropout Operation
In dropout, the internal PMOS switch is turned on continu-
ously (100% duty cycle) providing low dropout operation
with V
OUT
at V
IN
. Since the LTC1701 does not incorporate
an under voltage lockout, care should be taken to shut
down the LTC1701 for V
IN
< 2.5V.
APPLICATIO S U
U
W
U
The basic LTC1701 application circuit is shown in
Figure1. External component selection is driven by the
load requirement and begins with the selection of L1. Once
L1 is chosen, the Schottky diode D1 can be selected
followed by C
IN
and C
OUT
.
L Selection and Operating Frequency
The operating frequency is fixed by V
IN
, V
OUT
and the
constant off-time of about 500ns. The complete expres-
sion for operating frequency is given by:
f
O
=
+
V
V
V
V
T
IN
OUT
IN
D
OFF
1
Although the inductor does not influence the operating
frequency, the inductor value has a direct effect on ripple
current. The inductor ripple current
I
L
decreases with
higher inductance and increases with higher V
IN
or V
OUT
:
=
fL
+
+
I
V
V
V
V
V
V
L
IN
OUT
OUT
D
IN
D
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1701BES5 | 制造商:Linear Technology 功能描述:1.1 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO5 |
| LTC1701BES5#PBF | 制造商:Linear Technology 功能描述:Conv DC-DC Single Step Down 2.5V to 5.5V 5-Pin TSOT-23 制造商:Linear Technology 功能描述:DP-SWREG/Monolithic, CUT TAPE 1MHz Step-dn DC/DC Con in SOT-23 |
| LTC1701BES5#TR | 功能描述:IC REG BUCK ADJ 0.5A TSOT23-5 RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 標準包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關:600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應商設備封裝:8-SOIC |
| LTC1701BES5#TRM | 功能描述:IC REG BUCK ADJ 0.5A TSOT23-5 RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 標準包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關:600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應商設備封裝:8-SOIC |
| LTC1701BES5#TRMPBF | 功能描述:IC REG BUCK ADJ 0.5A TSOT23-5 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 標準包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關:600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應商設備封裝:8-SOIC |
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