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參數(shù)資料
| 型號： | LTC3714EG |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Intel Compatible, Wide Operating Range, Step-Down Controller with Internal Op Amp |
| 中文描述： | 2 A SWITCHING CONTROLLER, PDSO28 |
| 封裝： | 5.30 MM, PLASTIC, SSOP-28 |
| 文件頁數(shù)： | 22/28頁 |
| 文件大?。?/td> | 345K |
| 代理商： | LTC3714EG |
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LTC3714
22
3714f
APPLICATIOU
Because the top MOSFET is on for such a short time, a
single IRF7811 will be sufficient. Checking its power
dissipation at current limit with
ρ
80
°
C
= 1.2:
W
U
U
P
V
V
A
V
W
A
pF
=
kHz
W
W
TOP
=
(
) (
)
+
(
=
.
) (
+
)(
)(
0 652
.
)
1 15
24
1 7 24
0 299
20
1 2 0 013
.
20
0 353
.
60
300
2
.
.
.
T
J
= 50
°
C + (0.652W)(50
°
C/W) = 82.6
°
C
The junction temperatures will be significantly less at
nominal current, but this analysis shows that careful
attention to heat sinking will be necessary in this circuit.
C
IN
is chosen for an RMS current rating of about 6A at
temperature. The output capacitors are chosen for a low
ESR of 0.005
to minimize output voltage changes due to
inductor ripple current and load steps. The ripple voltage
will be only:
V
OUT(RIPPLE)
=
I
L(MAX)
(ESR) = (5.4A) (0.005
)
= 27mV
However, a 0A to 15A load step will cause an output
change of up to:
V
OUT(STEP)
=
I
LOAD
(ESR) = (15A) (0.005
) =
±
75mV
The complete circuit is shown in Figure 8.
Active Voltage Positioning
Active voltage positioning (also termed load “deregula-
tion” or droop) describes a technique where the output
voltage varies with load in a controlled manner. It is useful
in applications where rapid load steps are the main cause
of error in the output voltage. By positioning the output
voltage at or above the regulation point at zero load, and
below the regulation point at full load, one can use more
of the error budget for the load step. This allows one to
reduce the number of output capacitors by relaxing the
ESR requirement.
In the design example, Figure 8, five 0.025
capacitors
are required in parallel to keep the output voltage within
tolerance. Using active voltage positioning, the same
specification can be met with only
three
capacitors. In this
case, the load step will cause an output voltage change of:
=
(
)
(
)
=
V
A
mV
OUT STEP
(
)
.
15
1
3
0 025
125
By positioning the output voltage 60mV above the regula-
tion point at no load, it will drop 65mV below the regulation
point after the load step. However, when the load disap-
pears or the output is stepped from 15A to 0A, the 65mV
is recovered. This way, a total of 65mV change is observed
on V
OUT
in all conditions, whereas a total of
±
75mV or
150mV is seen on V
OUT
without voltage positioning.
Implementing active voltage positioning requires setting a
precise gain between the sensed current and the output
voltage. Because of the variability of MOSFET on-resis-
tance, it is prudent to use a sense resistor with active
voltage positioning. In order to minimize power lost in this
resistor, a low value of 0.003
is chosen. The nominal
sense voltage will now be:
V
SNS(NOM)
= (0.003
)(15A) = 45mV
To maintain a reasonable current limit, the voltage on the
V
RNG
pin is reduced to 0.5V by connecting it between
INTV
CC
and GND, corresponding to a 50mV nominal sense
voltage.
Next, the gain of the LTC3714 error amplifier must be
determined. The change in I
TH
voltage for a corresponding
change in the output current is:
=
.
=
( )
(
)(
)
=
I
V
V
R
I
A
V
TH
RNG
SENSE
OUT
12
15
1 08
.
The corresponding change in the output voltage is deter-
mined by the gain of the error amplifier and feedback
divider. The LTC3714 error amplifier has a
transconductance g
m
that is constant over both tempera-
ture and a wide
±
40mV input range. Thus, by connecting
a load resistance R
VP
to the I
TH
pin, the error amplifier gain
can be precisely set for accurate voltage positioning.
=
I
g R
V
V
V
TH
OUT
OUT
0 6
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3714EG#PBF | 功能描述:IC STP-DWN CNTRLR W/OPAMP 28SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標準包裝:2,000 系列:- 應用:控制器，DSP 輸入電壓:4.5 V ~ 25 V 輸出數(shù):2 輸出電壓:最低可調至 1.2V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:30-TFSOP（0.173"，4.40mm 寬） 供應商設備封裝:30-TSSOP 包裝:帶卷 (TR) |
| LTC3714EG#PBF | 制造商:Linear Technology 功能描述:DC/DC CONVERTER IC |
| LTC3714EG#TR | 功能描述:IC STP-DWN CNTRLR W/OPAMP 28SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標準包裝:43 系列:- 應用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應商設備封裝:48-QFN（7x7） 包裝:管件 |
| LTC3714EG#TRPBF | 功能描述:IC STP-DWN CNTRLR W/OPAMP 28SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標準包裝:43 系列:- 應用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應商設備封裝:48-QFN（7x7） 包裝:管件 |
| LTC3716EG | 功能描述:IC REG CTRLR BUCK PWM CM 36-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: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) |
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