- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄377765 > LTC1871 (Linear Technology Corporation) Quadruple 2-Input Positive-AND Gate 14-TVSOP -40 to 85 PDF資料下載
參數(shù)資料
| 型號： | LTC1871 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | Quadruple 2-Input Positive-AND Gate 14-TVSOP -40 to 85 |
| 中文描述： | 寬輸入范圍，無檢測電阻電流模式升壓，反激和SEPIC控制器 |
| 文件頁數(shù)： | 19/36頁 |
| 文件大?。?/td> | 411K |
| 代理商： | LTC1871 |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁當(dāng)前第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁第29頁第30頁第31頁第32頁第33頁第34頁第35頁第36頁
19
LTC1871
The output voltage ripple can increase during Burst Mode
operation if
I
L
is substantially less than I
BURST
. This can
occur if the input voltage is very low or if a very large
inductor is chosen. At high duty cycles, a skipped cycle
causes the inductor current to quickly decay to zero.
However, because
I
L
is small, it takes multiple cycles for
the current to ramp back up to I
BURST(PEAK)
. During this
inductor charging interval, the output capacitor must
supply the load current and a significant droop in the
output voltage can occur. Generally, it is a good idea to
choose a value of inductor
I
L
between 25% and 40% of
I
IN(MAX)
. The alternative is to either increase the value of
the output capacitor or disable Burst Mode operation
using the MODE/SYNC pin.
Burst Mode operation can be defeated by connecting the
MODE/SYNC pin to a high logic-level voltage (either with
a control input or by connecting this pin to INTV
CC
). In this
mode, the burst clamp is removed, and the chip can
operate at constant frequency from continuous conduc-
tion mode (CCM) at full load, down into deep discontinu-
ous conduction mode (DCM) at light load. Prior to skip-
ping pulses at very light load (i.e., <5% of full load), the
controller will operate with a minimum switch on-time in
DCM. Pulse skipping prevents a loss of control of the
output at very light loads and reduces output voltage
ripple.
Efficiency Considerations: How Much Does V
DS
Sensing Help
The efficiency of a switching regulator is equal to the
output power divided by the input power (
×
100%). Per-
cent efficiency can be expressed as:
% Efficiency = 100% – (L1 + L2 + L3 + …),
where L1, L2, etc. are the individual loss components as
a percentage of the 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 the majority of the losses in LTC1871 application
circuits:
1. The supply current into V
IN
. The V
IN
current is the sum
of the DC supply current I
Q
(given in the Electrical
Characteristics) and the MOSFET driver and control
currents. The DC supply current into the V
IN
pin is
typically about 550
μ
A and represents a small power
loss (much less than 1%) that increases with V
IN
. The
driver current results from switching the gate capaci-
tance of the power MOSFET; this current is typically
much larger than the DC current. Each time the MOSFET
is switched on and then off, a packet of gate charge Q
G
is transferred from INTV
CC
to ground. The resulting
dQ/dt is a current that must be supplied to the INTV
CC
capacitor through the V
IN
pin by an external supply. If
the IC is operating in CCM:
I
Q(TOT)
≈
I
Q
= f Q
G
P
IC
= V
IN
(I
Q
+ f Q
G
)
2. Power MOSFET switching and conduction losses. The
technique of using the voltage drop across the power
MOSFET to close the current feedback loop was chosen
because of the increased efficiency that results from not
having a sense resistor. The losses in the power MOSFET
are equal to:
P
I
D
R
D
k V
I
D
C
f
FET
O MAX
(
–
1
MAX
DS ON
(
MAX
T
O
O MAX
(
–
1
MAX
RSS
=
+
)
)
)
2
1.
ρ
The I
2
R power savings that result from not having a
discrete sense resistor can be calculated almost by
inspection.
P
I
D
R
D
R SENSE
(
O MAX
(
–
1
MAX
SENSE
MAX
)
)
=
2
To understand the magnitude of the improvement with
this V
DS
sensing technique, consider the 3.3V input, 5V
output power supply shown in Figure 1. The maximum
load current is 7A (10A peak) and the duty cycle is 39%.
Assuming a ripple current of 40%, the peak inductor
current is 13.8A and the average is 11.5A. With a
maximum sense voltage of about 140mV, the sense
APPLICATIOU
W
U
U
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LTC1871-7 | Quadruple 2-Input Positive-AND Gate 14-SOIC -40 to 85 |
| LTC1871EMS | Quadruple 2-Input Positive-AND Gate 14-SO -40 to 85 |
| LTC1873EG | Quadruple 2-Input Positive-AND Gate 14-TSSOP -40 to 85 |
| LTC1873 | Dual 550kHz Synchronous 2-Phase Switching Regulator Controller with 5-Bit VID(550kHz,雙 路,同步2相開關(guān)穩(wěn)壓器(帶5位VID)) |
| LTC1874 | Dual Constant Frequency Current Mode Step-Down DC/DC Controller(雙路(3.3V,1.8V輸出）恒定頻率，電流模式，步降DC/DC控制器) |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1871EMS | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC1871EMS#PBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| LTC1871EMS#TR | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC1871EMS#TRPBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC1871EMS-1#PBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。