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參數(shù)資料
| 型號： | LT3845AMPFE#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 4.40 MM, LEAD FREE, PLASTIC, TSSOP-16 |
| 文件頁數(shù)： | 13/26頁 |
| 文件大?。?/td> | 284K |
| 代理商： | LT3845AMPFE#PBF |
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LT3845A
20
3845afa
APPLICATIONS INFORMATION
Effective grounding techniques are critical for successful
DC/DC converter layouts. Orient power path components
such that current paths in the ground plane do not cross
through signal ground areas. Signal ground refers to the
Exposed Pad on the backside of the LT3845A IC in the
TSSOP package. SGND is referenced to the (–) terminal of
the VOUTdecouplingcapacitorandisusedastheconverter
voltage feedback reference. Power ground currents are
controlled on the LT3845A via the PGND pin, and this
ground references the high current synchronous switch
drive components, as well as the local VCC supply. It is
important to keep PGND and SGND voltages consistent
with each other, so separating these grounds with thin
traces is not recommended. When the synchronous
FET is turned on, gate drive surge currents return to the
LT3845APGNDpinfromtheFETsource.TheBOOSTsupply
refresh surge currents also return through this same path.
The synchronous FET must be oriented such that these
PGND return currents do not corrupt the SGND reference.
Problems caused by the PGND return path are generally
recognized during heavy load conditions, and are typically
evidenced as multiple switch pulses occurring during a
single switch cycle. This behavior indicates that SGND is
beingcorruptedandgroundingshouldbeimproved.SGND
corruption can often be eliminated, however, by adding a
small capacitor (100pF to 200pF) across the synchronous
switch FET from drain to source.
The high di/dt loop formed by the switch MOSFETs and
the input capacitor (CIN) should have short wide traces
to minimize high frequency noise and voltage stress from
inductiveringing.Surfacemountcomponentsarepreferred
to reduce parasitic inductances from component leads.
Connect the drain of the main switch MOSFET directly to
the (+) plate of CIN, and connect the source of the syn-
chronous switch MOSFET directly to the (–) terminal of
CIN. This capacitor provides the AC current to the switch
MOSFETs. Switch path currents can be controlled by
orienting switch FETs, the switched inductor, and input
and output decoupling capacitors in close proximity to
each other.
Locate the VCC and BOOST decoupling capacitors in close
proximity to the IC. These capacitors carry the MOSFET
drivers’ high peak currents. Locate the small-signal
components away from high frequency switching nodes
(BOOST, SW, TG, VCC and BG). Small-signal nodes are
oriented on the left side of the LT3845A, while high current
switching nodes are oriented on the right side of the IC
to simplify layout. This also helps prevent corruption of
the SGND reference.
Connect the VFB pin directly to the feedback resistors
independent of any other nodes, such as the SENSE– pin.
The feedback resistors should be connected between
the (+) and (–) terminals of the output capacitor (COUT).
Locate the feedback resistors in close proximity to the
LT3845A to minimize the length of the high impedance
VFB node.
TheSENSE–andSENSE+tracesshouldberoutedtogether
and kept as short as possible.
The LT3845A TSSOP package has been designed to
efficiently remove heat from the IC via the Exposed Pad on
the backside of the package. The Exposed Pad is soldered
to a copper footprint on the PCB. This footprint should be
made as large as possible to reduce the thermal resistance
of the IC case to ambient air. See Figure 5 for placement
of power path components.
Figure 5. Orientation of Components Isolates Power Path and
PGND Currents, Preventing Corruption of SGND Reference
BOOST
VCC
SW
PGND
SGND
LT3845A
SGND
REFERRED
COMPONENTS
+
BG
TG
VOUT
3845A AI03
VIN
ISENSE
SW
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相關(guān)代理商/技術(shù)參數(shù) |
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| LT3845EFE | 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Voltage Synchronous Current Mode Step-Down Controller with Adjustable Operating Frequency |
| LT3845EFE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標(biāo)準(zhǔn)包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 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:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| LT3845EFE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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: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) |
| LT3845EFEPBF | 制造商:Linear Technology 功能描述:60V Current-Mode Controller Adj. TSSOP16 |
| LT3845EFE-PBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Voltage Synchronous Current Mode Step-Down Controller with Adjustable Operating Frequency |
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