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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)： | 12/28頁 |
| 文件大?。?/td> | 345K |
| 代理商： | LTC3714EG |
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LTC3714
12
3714f
APPLICATIOU
The basic LTC3714 application circuit is shown in
Figure 1. External component selection is primarily de-
termined by the maximum load current and begins with
the selection of the sense resistance and power MOSFET
switches. The LTC3714 can use either a sense resistor or
the on-resistance of the synchronous power MOSFET for
determining the inductor current. The desired amount of
ripple current and operating frequency largely deter-
mines the inductor value. Finally, C
IN
is selected for its
ability to handle the large RMS current into the converter
and C
OUT
is chosen with low enough ESR to meet the
output voltage ripple and transient specification.
Maximum Sense Voltage and V
RNG
Pin
Inductor current is determined by measuring the voltage
across a sense resistance that appears between the PGND
and SENSE pins. The maximum sense voltage is set by the
voltage applied to the V
RNG
pin and is equal to approxi-
mately (0.133)V
RNG
. The current mode control loop will
not allow the inductor current valleys to exceed
(0.133)V
RNG
/R
SENSE
. In practice, one should allow some
margin for variations in the LTC3714 and external compo-
nent values and a good guide for selecting the sense
resistance is:
W
U
U
R
V
I
OUT MAX
(
SENSE
RNG
=
10
)
An external resistive divider from INTV
CC
can be used to
set the voltage of the V
RNG
pin between 0.5V and 2V
resulting in nominal sense voltages of 50mV to 200mV.
Additionally, the V
RNG
pin can be tied to SGND or INTV
CC
in which case the nominal sense voltage defaults to 70mV
or 140mV, respectively. The maximum allowed sense
voltage is about 1.33 times this nominal value.
Connecting the SENSE Pin
The LTC3714 can be used with or without a sense resistor.
When using a sense resistor, it is placed between the
source of the bottom MOSFET M2 and ground. Connect
the SENSE pin to the source of the bottom MOSFET so that
the resistor appears between the SENSE and PGND pins.
Using a sense resistor provides a well defined current
limit, but adds cost and reduces efficiency. Alternatively,
one can eliminate the sense resistor and use the bottom
MOSFET as the current sense element by simply connect-
ing the SENSE pin to the switch node SW at the drain of the
bottom MOSFET. This improves efficiency, but one must
carefully choose the MOSFET on-resistance as discussed
below.
Power MOSFET Selection
The LTC3714 requires two external N-channel power
MOSFETs, one for the top (main) switch and one for the
bottom (synchronous) switch. Important parameters for
the power MOSFETs are the breakdown voltage V
(BR)DSS
,
threshold voltage V
(GS)TH
, on-resistance R
DS(ON)
, reverse
transfer capacitance C
RSS
and maximum current I
DS(MAX)
.
The gate drive voltage is set by the 5V INTV
CC
supply.
Consequently, logic-level threshold MOSFETs must be
used in LTC3714 applications. If the input voltage is
expected to drop below 5V, then sub-logic level threshold
MOSFETs should be considered.
When the bottom MOSFET is used as the current sense
element, particular attention must be paid to its on-
resistance. MOSFET on-resistance is typically specified
with a maximum value R
DS(ON)(MAX)
at 25
°
C. In this case,
additional margin is required to accommodate the rise in
MOSFET on-resistance with temperature:
R
R
DS ON MAX
(
SENSE
ρ
T
)(
)
=
The
ρ
T
term is a normalization factor (unity at 25
°
C)
accounting for the significant variation in on-resistance
with temperature, typically about 0.4%/
°
C as shown in
Figure 3. Junction-to-case temperature is about 30
°
C in
most applications. For a maximum ambient temperature
of 70
°
C, using a value
ρ
100
°
C
= 1.3 is reasonable.
The power dissipated by the top and bottom MOSFETs
strongly depends upon their respective duty cycles and
the load current. When the LTC3714 is operating in
continuous mode, the duty cycles for the MOSFETs are:
D
V
V
D
V
V
V
TOP
OUT
IN
BOT
IN
OUT
IN
=
=
–
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相關代理商/技術參數(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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