參數(shù)資料
型號： LTC1159-5
廠商： Linear Technology Corporation
元件分類： 基準電壓源/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
文件頁數(shù)： 13/20頁
文件大?。?/td> 323K
代理商： LTC1159-5
13
LTC1159/LTC1159-3.3/LTC1159-5
APPLICATIU
low to high to low again, a packet of charge dQ moves
from V
CC
to ground. The resulting dQ/dt is a current out
of V
CC
which is typically much larger than the control
circuit current. In continuous mode, I
GATECHG
≈
f (Q
P
+
Q
N
), where Q
P
and Q
N
are the gate charges of the two
MOSFETs.
By powering EXTV
CC
from an output-derived source, the
additional V
IN
current resulting from the driver and
control currents will be scaled by a factor of
(Duty Cycle)/(Efficiency). For example in a 20V to 5V
application, 10mA of V
CC
current results in approxi-
mately 3mA of V
IN
current. This reduces the mid-current
loss from 10% or more (if the driver was powered
directly from V
IN
) to only a few percent.
3. I
2
R losses are easily predicted from the DC resistances
of the MOSFET, inductor, and current shunt. In con-
tinuous mode all of the output current flows through L
and R
SENSE
, but is “chopped” between the P-channel
and N-channel MOSFETs. If the two MOSFETs have
approximately the same R
DS(ON)
, then the resistance of
one MOSFET can simply be summed with the resis-
tances of L and R
SENSE
to obtain I
2
R losses. For
example, if each R
DS(ON)
= 0.1
, R
L
= 0.15
, and
R
SENSE
= 0.05
, then the total resistance is 0.3
. This
results in losses ranging from 3% to 12% as the output
current increases from 0.5A to 2A. I
2
R losses cause the
efficiency to roll-off at high output currents.
4. Transition losses apply only to the P-channel MOSFET,
and only when operating at high input voltages (typi-
cally 20V or greater). Transition losses can be esti-
mated from:
Transition Loss
≈
5(V
IN
)
2
(I
MAX
)(C
RSS
)(f)
Other losses including C
IN
and C
OUT
ESR dissipative losses,
Schottky conduction losses during dead time, and inductor
core losses, generally account for less than 2% total
additional loss.
W
U
U
LTC1159
SENSE
+
SENSE
–
9
8
1000pF
R1
100
R2
100
L
R
SENSE
+
C
OUT
R3
LTC1159 F07
Figure 7. Suppressing Burst Mode Operation
Auxiliary Windings – Suppressing Burst Mode
Operation
The LTC1159 synchronous switch removes the normal
limitation that power must be drawn from the inductor
primary winding in order to extract power from auxiliary
windings. With synchronous switching, auxiliary out-
puts may be loaded without regard to the primary output
load, providing that the loop remains in continuous
mode operation.
Burst Mode operation can be suppressed at low output
currents with a simple external network which cancels the
0.025V minimum current comparator threshold. This tech-
nique is also useful for eliminating audible noise from
certain types of inductors in high current (I
OUT
> 5A)
applications when they are lightly loaded.
An external offset is put in series with the Sense
–
pin to
subtract from the built-in 0.025V offset. An example of this
technique is shown in Figure 7. Two 100
resistors are
inserted in series with the leads from the sense resistor.
With the addition of R3, a current is generated through R1
causing an offset of:
)
If V
OFFSET
> 0.025V, the minimum threshold will be
cancelled and Burst Mode operation is prevented from
occurring. Since V
OFFSET
is constant, the maximum load
current is also decreased by the same offset. Thus, to get
back to the same I
MAX
, the value of the sense resistor must
be reduced:
75
I
MAX
To prevent noise spikes from erroneously tripping the
current comparator, a 1000pF capacitor is needed across
the Sense
–
and Sense
+
pins.
V
OFFSET
= V
OUT
)
R1
R1 + R3
R
SENSE
≈
m
相關(guān)PDF資料
PDF描述
LTC1159IS RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
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LTC1159IS-5 RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
LTC1174 High Efficiency Step-Down and Inverting DC/DC Converter(高效率,反相DC/DC變換器)
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相關(guān)代理商/技術(shù)參數(shù)
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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:- 標準包裝: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 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:6-WDFN 裸露焊盤 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:- 標準包裝: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 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:6-WDFN 裸露焊盤 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:- 標準包裝: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 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:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
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