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參數資料
| 型號： | LTC3856EFE#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, PDSO38 |
| 封裝： | 4.4 MM, LEAD FREE, PLASTIC, TSSOP-38 |
| 文件頁數： | 7/40頁 |
| 文件大?。?/td> | 2222K |
| 代理商： | LTC3856EFE#TRPBF |
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LTC3856
3856f
applicaTions inForMaTion
The Typical Application on the first page of this data sheet
is a basic LTC3856 application circuit. LTC3856 can be
configured to use either DCR (inductor resistance) sens-
ing or low value resistor sensing. The choice between the
two current sensing schemes is largely a design trade-off
between cost, power consumption and accuracy. DCR
sensing is becoming popular because it saves expensive
current sensing resistors and is more power efficient,
especially in high current applications. However, current
sensing resistors provide the most accurate current limits
for the controller. Other external component selection is
driven by the load requirement, and begins with the se-
lection of RSENSE (if RSENSE is used) and inductor value.
Next, the power MOSFETs are selected. Finally, input and
output capacitors are selected.
Current Limit Programming
The ILIM pin is a tri-level logic input which sets the maxi-
mum current limit of the controller. When ILIM is either
grounded, floated or tied to INTVCC, the typical value for
the maximum current sense threshold will be 30mV, 50mV
or 75mV, respectively.
Which setting should be used? For the best current limit
accuracy,usethe75mVsetting.The30mVsettingwillallow
for the use of very low DCR inductors or sense resistors,
but at the expense of current limit accuracy. The 50mV
setting is a good balance between the two.
SENSE+ and SENSE– Pins
The SENSE+ and SENSE– pins are the inputs to the current
comparators. The common mode input voltage range of
the current comparators is 0V to 5V. All SENSE+ pins are
high impedance inputs with small currents of less than
1A. The positive high impedance input to the current
comparatorsallowsaccurateDCRsensing.AllSENSE–pins
and DIFFP should be connected directly to VOUTwhenDCR
sensing is used. Care must be taken not to float these pins
during normal operation. Filter components mutual to the
sense lines should be placed close to the LTC3856, and
the sense lines should run close together to a Kelvin con-
nection underneath the current sense element (shown in
Figure 1). Sensing current elsewhere can effectively add
parasitic inductance and capacitance to the current sense
element, degrading the information at the sense terminals
and making the programmed current limit unpredictable.
If DCR sensing is used (Figure 2b), sense resistor R1
should be placed close to the switching node, to prevent
noise from coupling into sensitive small-signal nodes. The
capacitor C1 should be placed close to the IC pins.
Figure 1. Sense Lines Placement with Sense Resistor
COUT
TO SENSE FILTER,
NEXT TO THE CONTROLLER
RSENSE
3856 F01
VIN
INTVCC
BOOST
TG
SW
BG
PGND
FILTER COMPONENTS
PLACED NEAR SENSE PINS
SENSE+
SENSE–
SGND
LTC3856
VOUT
3856 F02a
CF 2RF ≤ ESL/RS
POLE-ZERO
CANCELLATION
SENSE RESISTOR
PLUS PARASITIC
INDUCTANCE
RS
ESL
CF
RF
(2a) Using a Resistor to Sense Current
(2b) Using the Inductor DCR to Sense Current
Figure 2. Two Different Methods of Sensing Current
VIN
INTVCC
BOOST
TG
SW
BG
PGND
*PLACE C1 NEAR SENSE+,
SENSE– PINS
INDUCTOR
DCR
L
SENSE+
SENSE–
SGND
LTC3856
VOUT
3856 F02b
R1
R2
C1*
R1||R2 × C1 =
L
DCR
RSENSE(EQ) = DCR
R2
R1 + R2
ITEMP
OPTIONAL
TEMP COMP
NETWORK
RP
RNTC
RS
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相關代理商/技術參數 |
參數描述 |
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| LTC3856EUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32WFQFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數: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) |
| LTC3856EUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 38-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數: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) |
| LTC3856IFE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 38TFSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數: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 |
| LTC3856IFE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 38TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數: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 |
| LTC3856IUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32WFQFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數: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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