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參數(shù)資料
| 型號： | 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 |
| 文件頁數(shù)： | 7/20頁 |
| 文件大?。?/td> | 323K |
| 代理商： | LTC1159-3. 3 |
7
LTC1159/LTC1159-3.3/LTC1159-5
APPLICATIU
The LTC1159 Compared to the LTC1148/LTC1149
Families
The LTC1159 family is closest in operation to the LTC1149
and shares much of the applications information. In addi-
tion to reduced quiescent and shutdown currents, the
LTC1159 adds an internal switch which allows the driver
and control sections to be powered from an external
source for higher efficiency. This change affects Power
MOSFET Selection, EXTV
CC
Pin Connection, Important
Information About LTC1159 Adjustable Applications, and
Efficiency Considerations found in this section.
The basic LTC1159 application circuit shown in Figure 1
is limited to a maximum input voltage of 30V due to
MOSFET breakdown. If the application does not require
greater than 18V operation, then the LTC1148 or
LTC1148HV should be used. For higher input voltages
where quiescent and shutdown current are not critical, the
LTC1149 may be a better choice since it is set up to drive
standard threshold MOSFETs.
W
U
U
both track I
MAX
. Once R
SENSE
has been chosen, I
BURST
and
I
SC(PK)
can be predicted from the following equations:
I
BURST
≈
15mV
R
SENSE
I
SC(PK)
= 150mV
R
SENSE
The LTC1159 automatically extends t
OFF
during a short
circuit to allow sufficient time for the inductor current to
decay between switch cycles. The resulting ripple current
causes the average short-circuit current I
SC(AVG)
to be
reduced to approximately I
MAX
.
R
SENSE
Selection for Output Current
R
SENSE
is chosen based on the required output current. The
LTC1159 current comparator has a threshold range which
extends from a minimum of 0.025V/R
SENSE
to a maximum
of 0.15V/R
SENSE
. The current comparator threshold sets
the peak of the inductor ripple current, yielding a maximum
output current I
MAX
equal to the peak value less half the
peak-to-peak ripple current. For proper Burst Mode opera-
tion,
RIPPLE(P-P)
must be ess han or equal o he minimum
current comparator threshold.
Since efficiency generally increases with ripple current,
the maximum allowable ripple current is assumed, i.e.,
I
RIPPLE(P-P)
= 0.025V/R
SENSE
(see C
T
and L Selection for
Operating Frequency). Solving for R
SENSE
and allowing
a margin for variations in the LTC1159 and external
component values yields:
100
I
MAX
A graph for selecting R
SENSE
versus maximum output
current is given in Figure 2. The LTC1159 series works well
with values of R
SENSE
from 0.02
to 0.2
.
The load current below which Burst Mode operation com-
mences, I
BURST
, and the peak short-circuit current, I
SC(PK)
,
R
SENSE
=
m
L and C
T
Selection for Operating Frequency
The LTC1159 uses a constant off-time architecture with
t
OFF
determined by an external timing capacitor C
T
. The
value of C
T
is calculated from the desired continuous mode
operating frequency, f:
)
1 – V
OUT
A graph for selecting C
T
versus frequency including the
effects of input voltage is given in Figure 3.
As the operating frequency is increased the gate charge
losses will be higher, reducing efficiency (see Efficiency
Considerations). The complete expression for operating
frequency is given by:
C
T
= 7.8
×
10
–5
f
)
V
IN
MAXIMUM OUTPUT CURRENT (A)
0
R
S
)
0.12
0.16
0.20
4
LTC1159 F02
0.08
0.04
0
1
2
3
5
0.10
0.14
0.18
0.06
0.02
Figure 2. R
SENSE
vs Maximum Output Current
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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(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 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(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 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(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 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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