參數(shù)資料
型號(hào)： LTC3853EUJ
廠商： LINEAR TECHNOLOGY CORP
元件分類： 穩(wěn)壓器
英文描述： 0.15 A DUAL SWITCHING CONTROLLER, 830 kHz SWITCHING FREQ-MAX, PQCC40
封裝： 6 X 6 MM, PLASTIC, QFN-40
文件頁(yè)數(shù)： 13/36頁(yè)
文件大?。?/td> 1780K
代理商： LTC3853EUJ
LTC3853
20
3853fa
ceramic capacitor placed directly adjacent to the INTVCC
and PGND pins is highly recommended. Good bypassing
is needed to supply the high transient currents required
by the MOSFET gate drivers and to prevent interaction
between the channels.
High input voltage applications in which large MOSFETs
are being driven at high frequencies may cause the maxi-
mum junction temperature rating for the LTC3853 to be
exceeded. The INTVCC current, which is dominated by the
gatechargecurrent,maybesuppliedbyeitherthe5Vlinear
regulator or EXTVCC. When the voltage on the EXTVCC pin
is less than 4.7V, the linear regulator is enabled. Power
dissipation for the IC in this case is highest and is equal
to VIN IINTVCC. The gate charge current is dependent
on operating frequency as discussed in the Efficiency
Considerations section. The junction temperature can be
estimated by using the equations given in Note 3 of the
ElectricalCharacteristics.Forexample,theLTC3853INTVCC
current is limited to less than 50mA from a 24V supply in
the UJ package and not using the EXTVCC supply:
TJ = 85°C + (50mA)(24V)(33°C/W) = 125°C
To prevent the maximum junction temperature from being
exceeded, the input supply current must be checked while
operatingincontinuousconductionmode(MODE/PLLIN=
SGND)atmaximumVIN.WhenthevoltageappliedtoEXTVCC
rises above 4.7V, the INTVCC linear regulator is turned off
and the EXTVCC is connected to the INTVCC. The EXTVCC
remainsonaslongasthevoltageappliedtoEXTVCCremains
above 4.5V. Using the EXTVCC allows the MOSFET driver
and control power to be derived from one of the LTC3853’s
switching regulator outputs during normal operation and
from the INTVCC when the output is out of regulation
(e.g., start-up, short-circuit). If more current is required
through the EXTVCCthanisspecified,anexternalSchottky
diode can be added between the EXTVCC and INTVCC pins.
Do not apply more than 6V to the EXTVCC pin and make
sure that EXTVCC < VIN.
Significant efficiency and thermal gains can be realized by
powering INTVCC from the output, since the VIN current
resultingfromthedriverandcontrolcurrentswillbescaled
by a factor of (Duty Cycle)/(Switcher Efficiency).
Tying the EXTVCC pin to a 5V supply reduces the junction
temperature in the previous example from 125°C to:
TJ = 85°C + (50mA)(5V)(33°C/W) = 94°C
However, for 3.3V and other low voltage outputs, addi-
tional circuitry is required to derive INTVCC power from
the output.
The following list summarizes the four possible connec-
tions for EXTVCC:
1. EXTVCC left open (or grounded). This will cause
INTVCC to be powered from the internal 5V regulator
resulting in an efficiency penalty of up to 10% at high
input voltages.
2. EXTVCC connected directly to VOUT. This is the
normal connection for a 5V regulator and provides
the highest efficiency.
3. EXTVCC connected to an external supply. If a 5V
external supply is available, it may be used to power
EXTVCC providing it is compatible with the MOSFET
gate drive requirements.
4. EXTVCC connected to an output-derived boost net-
work. For 3.3V and other low voltage regulators,
efficiency gains can still be realized by connecting
EXTVCC to an output-derived voltage that has been
boosted to greater than 4.7V.
For applications where the main input power is 5V, tie
the VIN and INTVCC pins together and tie the combined
pins to the 5V input with a 1Ω or 2.2Ω resistor as shown
in Figure 8 to minimize the voltage drop caused by the
gate charge current. This will override the INTVCC linear
regulator and will prevent INTVCC from dropping too low
due to the dropout voltage. Make sure the INTVCC voltage
is at or exceeds the RDS(ON) test voltage for the MOSFET
which is typically 4.5V for logic-level devices.
APPLICATIONS INFORMATION
INTVCC
LTC3853
RVIN
1
CIN
3853 F08
5V
CINTVCC
4.7F
+
VIN
Figure 8. Setup for a 5V Input
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LTC3853EUJ#PBF 功能描述:IC REG CTRLR BUCK PWM CM 40-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® 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(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 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(yè)面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR
LTC3853EUJ#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 40-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® 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(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 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(yè)面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR
LTC3853EUJPBF 制造商:Linear Technology 功能描述:DC-DC Controller Triple Buck 24V QFN40
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