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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)： | 15/28頁 |
| 文件大?。?/td> | 345K |
| 代理商： | LTC3714EG |
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LTC3714
15
3714f
The selection of C
OUT
is primarily determined by the ESR
required to minimize voltage ripple and load step
transients. The output ripple
V
OUT
is approximately
bounded by:
≤
+
V
I ESR
fC
OUT
OUT
1
8
Since
I
L
increases with input voltage, the output ripple is
highest at maximum input voltage. Typically, once the ESR
requirement is satisfied, the capacitance is adequate for
filtering and has the necessary RMS current rating.
Multiple capacitors placed in parallel may be needed to
meet the ESR and RMS current handling requirements.
Dry tantalum, special polymer, POSCAP aluminum elec-
trolytic and ceramic capacitors are all available in surface
mount packages. Special polymer capacitors offer very
low ESR but have lower capacitance density than other
types. Tantalum capacitors have the highest capacitance
density but it is important to only use types that have been
surge tested for use in switching power supplies. Alumi-
num electrolytic capacitors have significantly higher ESR,
but can be used in cost-sensitive applications providing
that consideration is given to ripple current ratings and
long term reliability. Ceramic capacitors have excellent
low ESR characteristics but can have a high voltage
coefficient and audible piezoelectric effects. The high Q of
ceramic capacitors with trace inductance can also lead to
significant ringing. When used as input capacitors, care
must be taken to ensure that ringing from inrush currents
and switching does not pose an overvoltage hazard to the
power switches and controller. High performance through-
hole capacitors may also be used, but an additional
ceramic capacitor in parallel is recommended to reduce
the effect of their lead inductance.
Top MOSFET Driver Supply (C
B
, D
B
)
An external bootstrap capacitor C
B
connected to the BOOST
pin supplies the gate drive voltage for the topside MOSFET.
This capacitor is charged through diode D
B
from INTV
CC
when the switch node is low. When the top MOSFET turns
on, the switch node rises to V
IN
and the BOOST pin rises
to approximately V
IN
+ INTV
CC
. The boost capacitor needs
APPLICATIOU
W
U
U
to store about 100 times the gate charge required by the
top MOSFET. In most applications 0.1
μ
F to 0.47
μ
F is
adequate.
Discontinuous Mode Operation and FCB Pin
The FCB pin determines whether the bottom MOSFET
remains on when current reverses in the inductor. Tying
this pin above its 0.6V threshold (typically to INTV
CC
)
enables discontinuous operation where the bottom
MOSFET turns off when inductor current reverses. The
load current at which current reverses and discontinuous
operation begins, depends on the amplitude of the induc-
tor ripple current. The ripple current depends on the
choice of inductor value and operating frequency as well
as the input and output voltages.
Tying the FCB pin below the 0.6V threshold forces continu-
ous synchronous operation, allowing current to reverse at
light loads.
In addition to providing a logic input to force continuous
operation, the FCB pin provides a means to maintain a
flyback winding output when the primary is operating in
discontinuous mode. The secondary output V
SEC
is nor-
mally set as shown in Figure 5 by the turns ratio N of the
transformer. However, if the controller goes into discon-
tinuous mode and halts switching due to a light primary
load current, then V
SEC
will droop. An external resistor
divider from V
SEC
to the FCB pin sets a minimum voltage
V
SEC(MIN)
below which continuous operation is forced
until V
SEC
has risen above its minimum.
V
V
R
R
SEC MIN
(
)
.
=
+
0 6
1
4
3
V
IN
SENSE
LTC3714
EXTV
CC
SGND
FCB
TG
SW
OPTIONAL
EXTV
CC
CONNECTION
5V < V
SEC
< 7V
R3
R4
3714 F05
T1
1:N
BG
PGND
+
C
SEC
1
μ
F
V
OUT
V
SEC
V
IN
+
C
IN
1N4148
+
C
OUT
Figure 5. Secondary Output Loop and EXTV
CC
Connection
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相關(guān)代理商/技術(shù)參數(shù) |
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| 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(yīng)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(diào)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(yīng)商設(shè)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(yīng)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(yīng)商設(shè)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(yīng)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(yīng)商設(shè)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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