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參數(shù)資料
| 型號： | LT3957IUHE#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING REGULATOR, PQCC36 |
| 封裝： | 5 X 6 MM, LEAD FREE, PLASTIC, QFN-36 |
| 文件頁數(shù)： | 2/28頁 |
| 文件大?。?/td> | 359K |
| 代理商： | LT3957IUHE#PBF |
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LT3957
10
3957f
APPLICATIONS INFORMATION
INTVCC Regulator Bypassing and Operation
An internal, low dropout (LDO) voltage regulator produces
the 5.2V INTVCC supply which powers the gate driver, as
shown in Figure 1. The LT3957 contains an undervoltage
lockout comparator A8 for the INTVCC supply. The INTVCC
undervoltage (UV) threshold is 2.7V (typical), with 0.1V
hysteresis, to ensure that the internal MOSFET has suf-
cient gate drive voltage before turning on. When INTVCC
is below the UV threshold, the internal power switch will
be turned off and the soft-start operation will be triggered.
The logic circuitry within the LT3957 is also powered from
the internal INTVCC supply.
The INTVCC regulator must be bypassed to SGND imme-
diately adjacent to the IC pins with a minimum of 4.7μF
ceramic capacitor. Good bypassing is necessary to supply
the high transient currents required by the MOSFET gate
driver.
In an actual application, most of the IC supply current is
used to drive the gate capacitance of the internal power
MOSFET. The on-chip power dissipation can be signicant
when the internal power MOSFET is being driven at a high
frequency and the VIN voltage is high.
An effective approach to reduce the power consumption of
the internal LDO for gate drive and to improve the efciency
is to tie the INTVCC pin to an external voltage source high
enough to turn off the internal LDO regulator.
In SEPIC or yback applications, the INTVCC pin can be
connected to the output voltage VOUT through a blocking
diode, as shown in Figure 2, if VOUT meets the following
conditions:
1. VOUT < VIN (pin voltage)
2. VOUT < 8V
A resistor RVCC can be connected, as shown in Figure 2, to
limit the inrush current from VOUT. Regardless of whether
or not the INTVCC pin is connected to an external voltage
source, it is always necessary to have the driver circuitry
bypassed with a 4.7μF low ESR ceramic capacitor to ground
immediately adjacent to the INTVCC and SGND pins.
If LT3957 operates at a low VIN and high switching fre-
quency, the voltage drop across the drain and the source of
the LDO PMOS (M2 in Figure 1) could push INTVCC to be
below the UV threshold. To prevent this from happening,
the INTVCC pin can be shorted directly to the VIN pin. VIN
must not exceed the INTVCC Absolute Maximum Rating
(8V). In this condition, the internal LDO will be turned off
and the gate driver will be powered directly from VIN. It is
recommended that INTVCC pin be shorted to the VIN pin if
VIN is lower than 3.5V at 1MHz switching frequency, or VIN
is lower than 3.2V at 100kHz switching frequency. With
the INTVCC pin shorted to VIN, however, a small current
(around 16μA) will load the INTVCC in shutdown mode.
Figure 2. Connecting INTVCC to VOUT
CVCC
4.7μF
VOUT
3957 F02
INTVCC
SGND
LT3957
RVCC
DVCC
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LT3958IUHE#PBF | SWITCHING REGULATOR, PQCC36 |
| LT3958EUHE#PBF | SWITCHING REGULATOR, PQCC36 |
| LT3958EUHE#TRPBF | SWITCHING REGULATOR, PQCC36 |
| LT4180MPGN#PBF | POWER SUPPLY SUPPORT CKT, PDSO24 |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT3957IUHETRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch |
| LT3958 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Monolithic High Voltage Isolated Flyback Converter No External Start-Up Resistor |
| LT3958EUHE#PBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:250 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V 輸入電壓:2.05 V ~ 6 V PWM 型:電壓模式 頻率 - 開關(guān):2MHz 電流 - 輸出:500mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:6-UFDFN 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:6-SON（1.45x1） 產(chǎn)品目錄頁面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2 |
| LT3958EUHE#PBF | 制造商:Linear Technology 功能描述:IC BOOST/FLYBACK/SEPIC/INVERT CTRL QFN36 |
| LT3958EUHE#TRPBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
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