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參數(shù)資料
| 型號： | LT3645EMSE#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1.25 A SWITCHING REGULATOR, 825 kHz SWITCHING FREQ-MAX, PDSO12 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-12 |
| 文件頁數(shù)： | 24/24頁 |
| 文件大?。?/td> | 296K |
| 代理商： | LT3645EMSE#TRPBF |
LT3645
9
3645f
OPERATION
The LT3645 includes a constant frequency, current mode
step-down buck switching regulator together with a low-
dropout regulator (LDO).
If EN/UVLO is less than ~0.7V, both the buck and LDO
are off, the output is disconnected and the input current
is less than 2μA. The buck turns on when EN/UVLO is
greater than 1.23V. An undervoltage lockout (UVLO)
turns the buck and LDO off when VIN is less than 3.4V.
An overvoltage lockout (OVLO) turns the buck and LDO
off when VIN is greater than 38.5V. The part will withstand
nonrepetitive one second input voltage transients up to
55V. An internal thermal shutdown circuit monitors the die
temperature and shuts both the buck and LDO off if the
die temperature exceeds ~160°C. The thermal shutdown
has 10 degrees of hysteresis.
An internal regulator provides power to the control circuitry
and produces the 0.8V feedback voltage for the buck and
LDO error ampliers.
An internal, xed-frequency oscillator in the step-down
regulator enables an RS ip-op, turning on the internal
power switch Q1. A comparator monitors the current
owing between the VIN and SW pins, turning the switch
off when this current reaches a level determined by the
voltage at VCandtheinternalslope-compensation.Anerror
amplier servos the VC node. The output of an external
resistor divider between OUT and ground is tied to the
VFB pin and presented to the negative error amp input.
The positive input to the error amp is a 0.8V reference, so
the voltage loop forces the VFB pin to 0.8V. The reference
voltage of the buck error amplier is ramped over 900μs
during the soft-start period. When VC rises, it results in an
increase in output current, and when VC falls, it results in
less output current. Current limit is provided by an active
clamp on the VC node.
The buck power switch (Q1) is driven from the BOOST
pin. An external capacitor and internal diode are used to
generate a voltage at the BOOST pin that is higher than the
input supply, which allows the driver to fully saturate the
internal bipolar NPN power switch for efcient operation.
An external diode can be used to make the BOOST drive
more effective at low output voltages.
The oscillator reduces the LT3645’s operating frequency
during the soft-start period. This frequency foldback helps
to control the output current during startup.
The current in the external catch diode (D1) is sensed
through the DA pin. If the catch diode current exceeds
0.9A, the oscillator frequency is decreased. This prevents
current runaway during startup or overload.
The LDO only operates if EN/UVLO is greater than 1.23V
and EN2 is greater than 1.3V. If EN/UVLO is low and EN2
is high, the LDO will not start. When EN2 > 1.3V and EN/
UVLO > 1.23V, the LDO power transistor will turn on and
regulate the output at the OUT2 pin. An error amplier
driving Q2 has its positive input at the 0.797V reference.
The output of an external resistor divider between OUT2
and ground is tied to the VFB2 pin and presented to the
negative error amp input, forcing the VFB2 pin to 0.797V.
The reference voltage of the LDO error amplier is ramped
over 600μs during the soft-start period. The LDO power
transistor (Q2) is driven from the VIN pin. Q2 is a bipolar
NPN which draws its collector current from the VCC2 pin.
The NPG pin is an open-collector output that indicates
when both buck and LDO outputs are in at least 90% in
regulation. When FB and FB2 rise above 720mV, the NPG
pin is pulled low.
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相關代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT3645EUD#PBF | 功能描述:IC REG DL BUCK/LINEAR 16-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標準包裝:2,500 系列:- 拓撲:降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關:300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應商設備封裝:* 包裝:* |
| LT3645EUD#TRPBF | 功能描述:IC REG DL BUCK/LINEAR 16-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標準包裝:2,500 系列:- 拓撲:降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關:300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應商設備封裝:* 包裝:* |
| LT3645HMSE#PBF | 功能描述:IC REG DL BUCK/LINEAR 12-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標準包裝:2,500 系列:- 拓撲:降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關:300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應商設備封裝:* 包裝:* |
| LT3645HMSE#TRPBF | 功能描述:IC REG DL BUCK/LINEAR 12-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標準包裝:2,500 系列:- 拓撲:降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關:300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應商設備封裝:* 包裝:* |
| LT3645IMSE#PBF | 功能描述:IC REG DL BUCK/LINEAR 12-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標準包裝:2,500 系列:- 拓撲:降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關:300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應商設備封裝:* 包裝:* |
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