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参数资料
| 型号： | LTC3829EUHF#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, PQCC38 |
| 封装： | 5 X 7 MM, LEAD FREE, PLASTIC, M0-220WHKD, QFN-38 |
| 文件页数： | 22/40页 |
| 文件大小： | 478K |
| 代理商： | LTC3829EUHF#PBF |
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LTC3829
3829f
applicaTions inForMaTion
INTVCC (LDO) and EXTVCC
TheLTC3829featuresatruePMOSLDOthatsuppliespower
to INTVCC from the VIN supply. INTVCC powers the gate
drivers and much of the LTC3829’s internal circuitry. The
LDO regulates the voltage at the INTVCCpinto5VwhenVIN
is greater than 5.5V. EXTVCC connects to INTVCC through
a P-channel MOSFET and can supply the needed power
when its voltage is higher than 4.7V. Each of these can
supply a peak current of 100mA and must be bypassed
to ground with a minimum of 4.7F ceramic capacitor or
low ESR electrolytic capacitor. No matter what type of bulk
capacitor is used, an additional 0.1F ceramic capacitor
placed directly adjacent to the INTVCC and PGND pins is
highlyrecommended.Goodbypassingisneededtosupply
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 LTC3829 to be
exceeded. The INTVCC current, which is dominated by the
gate charge current, may be supplied by either the 5V LDO
or EXTVCC. When the voltage on the EXTVCC pin is less
than 4.7V, the LDO 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 Electrical Characteristics
tables. For example, the LTC3829 INTVCCcurrentislimited
to less than 42mA from a 38V supply in the UHF package
and not using the EXTVCC supply:
TJ = 70°C + (42mA)(38V)(34°C/W) = 125°C
To prevent the maximum junction temperature from be-
ing exceeded, the input supply current must be checked
while operating in continuous conduction mode (MODE
= SGND) at maximum VIN. When the voltage applied to
EXTVCC rises above 4.7V, the INTVCC LDO 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 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
EXTVCC than is specified, an external Schottky 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 cur-
rent resulting from the driver and control currents will be
scaled 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 = 70°C + (42mA)(5V)(34°C/W) = 77°C
However, for low voltage outputs, additional circuitry is
required to derive INTVCC power from the output.
The following list summarizes the four possible connec-
tions for EXTVCC:
1. EXTVCCleftopen(orgrounded).ThiswillcauseINTVCC
to be powered from the internal 5V LDO 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. EXTVCCconnectedtoanexternalsupply.Ifa5Vexternal
supply is available, it may be used to power EXTVCC
providing it is compatible with the MOSFET gate drive
requirements.
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相关代理商/技术参数 |
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| LTC3829IFE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 38TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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