參數(shù)資料
型號(hào)： LTC1159-3. 3
廠商： Linear Technology Corporation
元件分類： 基準(zhǔn)電壓源/電流源
英文描述： 500kHz and 1MHz High Efficiency 1.5A Switching Regulators; Package: SO; No of Pins: 8; Temperature Range: -40?°C to 85?°C
中文描述： 射頻放大器
文件頁(yè)數(shù)： 8/20頁(yè)
文件大?。?/td> 323K
代理商： LTC1159-3. 3
8
LTC1159/LTC1159-3.3/LTC1159-5
APPLICATIU
W
U
U
inductance collapses abruptly when the peak design cur-
rent is exceeded. This results in an abrupt increase in
inductor ripple current and consequent output voltage
ripple which can cause Burst Mode operation to be falsely
triggered in the LTC1159. Do not allow the core to saturate!
Molypermalloy (from Magnetics, Inc.) is a low loss core
material for toroids, but it is more expensive than ferrite.
A reasonable compromise from the same manufacturer is
Kool M
μ
. Toroids are very space efficient, especially when
you can use several layers of wire. Because they generally
lack a bobbin, mounting is more difficult. However, new
surface mount designs available from Coiltronics do not
increase the height significantly.
Power MOSFET Selection
Two external power MOSFETs must be selected for use
with the LTC1159: a P-channel MOSFET for the main
switch and an N-channel MOSFET for the synchronous
switch.
The peak-to-peak drive levels are set by the V
CC
voltage on
the LTC1159. This voltage is typically 4.5V during start-up
and 5V to 7V during normal operation (see EXTV
CC
Pin
Connection). Consequently, logic-level threshold
MOSFETs must be used in most LTC1159 family applica-
tions The only exception is applications in which EXTV
CC
is powered from an external supply greater than 8V, in
which standard threshold MOSFETs (V
GS(TH)
< 4V) may be
used. Pay close attention to the BV
DSS
specification for the
MOSFETs as well; many of the logic-level MOSFETs are
limited to 30V.
Selection criteria for the power MOSFETs include the “ON”
resistance R
DS(ON)
, reverse transfer capacitance C
RSS
,
input voltage, and maximum output current. When the
LTC1159 is operating in continuous mode, the duty cycle
for the P-channel MOSFET is given by:
P-Ch Duty Cycle =V
OUT
V
IN
N-Ch Duty Cycle =V
IN
–
V
OUT
V
IN
The MOSFET dissipations at maximum output current are
given by:
f =
1
t
OFF
)
)
1 –V
OUT
V
IN
where t
OFF
= 1.3
×
10
4
×
C
T
Once the frequency has been set by C
T
, the inductor L
must be chosen to provide no more than 0.025V/R
SENSE
of peak-to-peak inductor ripple current. This results in a
minimum required inductor value of:
L
MIN
= 5.1
×
10
5
×
R
SENSE
×
C
T
×
V
REG
As the inductor value is increased from the minimum value,
the ESR requirements for the output capacitor are eased at
the expense of efficiency. If too small an inductor is used,
the LTC1159 may not enter Burst Mode operation and
efficiency will be severely degraded at low currents.
Inductor Core Selection
Once the minimum value for L is known, the type of
inductor must be selected. High efficiency converters
generally cannot afford 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 the inductance selected. As induc-
tance increases, core losses go down but copper (I
2
R)
losses will increase.
Ferrite designs have very low core loss, so design goals can
concentrate on copper loss and preventing saturation.
Ferrite core material saturates “hard,” which means that
FREQUENCY (kHz)
0
0
C
T
200
400
600
1400
1000
50
100
1200
800
150
200
250
V
OUT
= 5V
V
IN
= 48V
V
IN
= 12V
V
IN
= 24V
LTC1159 F03
Figure 3. Timing Capacitor Selection
Kool M
μ
is a registered trademark of Magnetics, Inc.
相關(guān)PDF資料
PDF描述
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC1159-5 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Efficiency Synchronous Step-Down Switching Regulators
LTC1159CG 功能描述:IC REG CTRLR BUCK PWM CM 20-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(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC1159CG#PBF 功能描述:IC REG CTRLR BUCK PWM CM 20-SSOP 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: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(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC1159CG#TR 功能描述:IC REG CTRLR BUCK PWM CM 20-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(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC1159CG#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 20-SSOP 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:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 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 ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
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