- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄377763 > LTC1773 (Linear Technology Corporation) Synchronous Step-Down Regulator Controller(同步步降穩(wěn)壓器) PDF資料下載
參數(shù)資料
| 型號(hào)： | LTC1773 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | Synchronous Step-Down Regulator Controller(同步步降穩(wěn)壓器) |
| 中文描述： | 同步降壓穩(wěn)壓控制器（同步步降穩(wěn)壓器） |
| 文件頁(yè)數(shù)： | 8/20頁(yè) |
| 文件大?。?/td> | 274K |
| 代理商： | LTC1773 |
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)當(dāng)前第8頁(yè)第9頁(yè)第10頁(yè)第11頁(yè)第12頁(yè)第13頁(yè)第14頁(yè)第15頁(yè)第16頁(yè)第17頁(yè)第18頁(yè)第19頁(yè)第20頁(yè)
LTC1773
8
inductor ripple current and consequent output voltage
ripple. Do not allow the core to saturate!
Molypermalloy (from Magnetics, Inc.) is a very good, low
loss core material for toroids, but it is more expensive than
ferrite. A reasonable compromise from the same manu-
facturer is Kool M
μ
. Toroids are very space efficient,
especially when you can use several layers of wire. Be-
cause they generally lack a bobbin, mounting is more
difficult. However, new designs for surface mount are
available which do not increase the height significantly.
Power MOSFET and Schottky Diode Selection
Two external power MOSFETs must be selected for use
with the LTC1773: a P-channel MOSFET for the top (main)
switch, and an N-channel MOSFET for the bottom (syn-
chronous) switch.
The peak-to-peak gate drive levels are set by the V
IN
voltage. Therefore, for V
IN
> 5V, logic-level threshold
MOSFETs should be used. But, for V
IN
< 5V, sub-logic
level threshold MOSFETs (V
GS(TH)
< 3V) should be used.
In these applications, make sure that the V
IN
to the
LTC1773 is less than 8V because the absolute maximum
V
GS
rating of the majority of these sub-logic threshold
MOSFETs is 8V.
Selection criteria for the power MOSFETs include the “ON”
resistance R
DS(ON)
, reverse transfer capacitance C
RSS
,
input voltage, maximum output current, and total gate
charge. When the LTC1773 is operating in continuous
mode the duty cycles for the top and bottom MOSFETs are
given by:
Main Switch Duty Cycle = V
OUT
/V
IN
Synchronous Switch Duty Cycle = (V
IN
– V
OUT
)/V
IN
The MOSFET power dissipations at maximum output
current are given by:
P
V
V
I
R
)
K V
I
C
f
MAIN
OUT
IN
MAX
DSON
IN
MAX
RSS
=
(
)
+
(
+
) (
)(
)( )
2
2
1
δ
APPLICATIO
S I
N
FOR
ATIO
U
The operating frequency and inductor selection are inter-
related in that higher operating frequencies allow the use
of smaller inductor and capacitor values. However, oper-
ating at a higher frequency generally results in lower
efficiency because of external MOSFET gate charge losses.
The inductor value has a direct effect on ripple current. The
ripple current,
I
L
, decreases with higher inductance or
frequency and increases with higher V
IN
or V
OUT
.
W
U
Kool M
μ
is a registered trademark of Magnetics, Inc.
I
f L
V
V
V
L
OUT
OUT
IN
=
( )( )
1
1–
(1)
Accepting larger values of
I
L
allows the use of lower
inductances, but results in higher output voltage ripple
and greater core losses. A reasonable starting point for
setting ripple current is 30% to 40% of I
MAX
. Remember,
the maximum
I
L
occurs at the maximum input voltage.
The inductor value also has an effect on Burst Mode
operation. The transition to low current operation begins
when the inductor current peaks fall to approximately 1/3
its original value. Lower inductor values (higher
I
L
) will
cause this to occur at lower load currents, which can cause
a dip in efficiency in the upper range of low current
operation. In Burst Mode operation, lower inductance
values will cause the burst frequency to increase.
Inductor Core Selection
Once the value for L is known, the type of inductor must be
selected. High efficiency converters generally cannot af-
ford the core loss found in low cost powdered iron cores,
forcing the use of more expensive ferrite, molypermalloy,
or Kool M
μ
cores. Actual core loss is independent of core
size for a fixed inductor value, but it is very dependent on
inductance selected. As inductance increases, core losses
go down. Unfortunately, increased inductance requires
more turns of wire and therefore copper losses will in-
crease. Ferrite designs have very low core losses and are
preferred at high switching frequencies, so design goals
can concentrate on copper loss and preventing saturation.
Ferrite core material saturates “hard”, which means that
inductance collapses abruptly when the peak design cur-
rent is exceeded. This results in an abrupt increase in
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LTC1775C | Quadruple 2-Input Positive-NAND Gate 14-TVSOP -40 to 85 |
| LTC1775IGN | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LTC1775CGN | Quadruple 2-Input Positive-NAND Gate 14-TVSOP -40 to 85 |
| LTC1775CS | Quadruple 2-Input Positive-NAND Gate 14-SOIC -40 to 85 |
| LTC1775I | Quadruple 2-Input Positive-NAND Gate 14-SOIC -40 to 85 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1773EMS | 功能描述:IC REG CTRLR BUCK 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) |
| LTC1773EMS#PBF | 功能描述:IC REG CTRLR BUCK 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 |
| LTC1773EMS#TR | 功能描述:IC REG CTRLR BUCK 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) |
| LTC1773EMS#TRPBF | 功能描述:IC REG CTRLR BUCK 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) |
| LTC1775CGN | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 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:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。