- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄377761 > LTC1700 (Linear Technology Corporation) Quadruple 2-Input Exclusive-OR Gates 14-SO 0 to 70 PDF資料下載
參數(shù)資料
| 型號(hào)： | LTC1700 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | Quadruple 2-Input Exclusive-OR Gates 14-SO 0 to 70 |
| 中文描述： | 無(wú)檢測(cè)電阻同步升壓型DC / DC控制器 |
| 文件頁(yè)數(shù)： | 12/16頁(yè) |
| 文件大?。?/td> | 194K |
| 代理商： | LTC1700 |
第1頁(yè)第2頁(yè)第3頁(yè)第4頁(yè)第5頁(yè)第6頁(yè)第7頁(yè)第8頁(yè)第9頁(yè)第10頁(yè)第11頁(yè)當(dāng)前第12頁(yè)第13頁(yè)第14頁(yè)第15頁(yè)第16頁(yè)
LTC1700
12
Efficiency Considerations
The efficiency of a switching regulator is equal to the
output power divided by the input power (
×
100%).
Percent efficiency can be expressed as:
% Efficiency = 100%–(L1 + L2 + L3 + ...)
where L1, L2, etc. are the individual losses as a percentage
of input power. It is often useful to analyze individual
losses to determine what is limiting the efficiency and
which change would produce the most improvement.
Although all dissipative elements in the circuit produce
losses, four
main sources usually account for most of the
losses in LTC1700 circuits:
1. LTC1700 supply current. This DC supply current, given
in the electrical characteristics, excludes MOSFET drivers
and control current. This supply current results in a small
loss which increases with V
OUT
.
2. MOSFETs gate charge current results from switching
the gate capacitance of the power MOSFETs. Each time a
MOSFET gate is switched on and then off, a packet of gate
charge Q
g
moves from V
OUT
to ground. The resulting
current out from V
OUT
is typically much larger than the
control circuit current. In continuous mode, I
GATECHG
=
f(Q
g(TOP)
+ Q
g(BOT)
). At high switching frequencies, this
loss becomes increasing important.
3. DC I
2
R Losses. Since there is no sense resistor needed,
DC I
2
R losses arise only from the resistances of the
MOSFETs and inductor. In continuous mode, the average
current flows through the inductor but is “chopped”
between the synchronous P-channel MOSFET and the
main N-channel MOSFET. If the two MOSFETs have ap-
proximately the same R
DS(ON)
, then the resistance of one
MOSFET can simply be summed with the resistance of the
inductor to obtain the DC I
2
R loss. For example, if each
R
DS(ON)
= 0.05
and R
L
= 0.15
, then the total resistance
is 0.2
. This results in losses ranging from 2% to 8% as
the output current increases from 0.5A to 2A for a 5V
output. I
2
R losses cause the efficiency to drop at high
output currents.
4. Transition losses apply to the main external MOSFET
and increase at higher operating frequencies and output
voltages. Transition losses can be estimated from:
Transition Loss = 2.5(V
OUT
)
2
I
O(MAX)
C
RSS
(f)
Other losses including C
IN
and C
OUT
ESR dissipative
losses, and inductor core losses, generally account for
less than 2% total loss.
Run/Soft Start Function
The RUN/SS pin is a dual purpose pin that provides the
soft-start function and a means to shut down the LTC1700.
Soft-start reduces input surge current from V
IN
by gradu-
ally increasing the internal current limit. Power supply
sequencing can also be accomplished using this pin.
An internal 3.8
μ
A current source charges up an external
capacitor C
SS
. When the voltage on the RUN/SS pin
reaches 0.7V, the LTC1700 begins operating. As the
voltage on RUN/SS continues to ramp from 0.7V to 1V, the
internal current limit is also ramped at a proportional linear
rate. The current limit begins near 0A (at V
RUN/SS
= 0.7V)
and ends at 0.078/R
DS(ON)
(V
RUN/SS
≈
2.2V). The output
current thus ramps up slowly, reducing the starting surge
current required from the input power supply. If the RUN/
SS has been pulled all the way to ground, there will be a
delay before the current limit starts increasing and is given
by:
t
DELAY
= 1.13C
SS
/I
CHG
For input voltages less than 2.3V during the start-up
duration, the soft-start function has no effect on the
internal 60mA current limit. Therefore to fully take advan-
tage of this feature, the soft-start capacitor has to be sized
accordingly to account for the time it takes V
OUT
to reach
2.3V. An approximate mathematical representation for the
time it takes V
OUT
to reach 2.3V upon powering up is given
by:
t
C
V
V
L
V
I
POWER UP
OUT
IN
D
IN
OUT
=
( . –
( )
2. –
–
)
–
2 3
260
APPLICATIO
S I
FOR
ATIO
U
W
U
U
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LTC1700EMS | Synchronous 8-Bit Up/Down Binary Counters 24-SOIC 0 to 70 |
| LTC1702CGN | Dual 550kHz Synchronous 2-Phase Switching Regulator Controller |
| LTC1702 | Synchronous 8-Bit Up/Down Binary Counters 24-SOIC 0 to 70 |
| LTC1702C | Synchronous 8-Bit Up/Down Binary Counters 24-SOIC 0 to 70 |
| LTC1702I | Synchronous 8-Bit Up/Down Binary Counters 24-SOIC 0 to 70 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1700EMS | 功能描述:IC REG CTRLR BST PWM CM 10-MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC1700EMS#PBF | 功能描述:IC REG CTRLR BST PWM CM 10-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標(biāo)準(zhǔn)包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁(yè)面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| LTC1700EMS#TR | 功能描述:IC REG CTRLR BST PWM CM 10-MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC1700EMS#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 10-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC1701BES5 | 制造商:Linear Technology 功能描述:1.1 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO5 |
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。