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參數(shù)資料
| 型號： | LT3800 |
| 廠商： | Linear Technology Corporation |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| 中文描述： | 抗輻射高效，5安培開關穩(wěn)壓器 |
| 文件頁數(shù)： | 10/24頁 |
| 文件大小： | 240K |
| 代理商： | LT3800 |
LT3724
10
3724f
start of the next cycle or until the bootstrapped capacitor
is fully charged.
MOSFET Driver
The LT3724 contains a high speed boosted driver to turn
on and off an external N-channel MOSFET switch. The
MOSFET driver derives its power from the boost capacitor
which is referenced to the SW pin and the source of the
MOSFET. The driver provides a large pulse of current to
turn on the MOSFET fast to minimize transition times.
Multiple MOSFETs can be paralleled for higher current
operation.
To eliminate the possibility of shoot through between the
MOSFET and the internal SW pull-down switch, an adap-
tive nonoverlap circuit ensures that the internal pull-down
switch does not turn on until the gate of the MOSFET is
below its turn on threshold.
Low Current Operation (Burst Mode Operation)
To increase low current load efficiency, the LT3724 is
capable of operating in Linear Technology’s proprietary
Burst Mode operation where the external MOSFET oper-
ates intermittently based on load current demand. The
Burst Mode function is disabled by connecting the
BURST_EN pin to V
CC
and enabled by connecting the pin
to SGND.
When the required switch current, sensed via the V
C
pin
voltage, is below 15% of maximum, Burst Mode operation
is employed and that level of sense current is latched onto
the IC control path. If the output load requires less than
this latched current level, the converter will overdrive the
output slightly during each switch cycle. This overdrive
condition is sensed internally and forces the voltage on the
V
C
pin to continue to drop. When the voltage on V
C
drops
150mV below the 15% load level, switching is disabled,
and the LT3724 shuts down most of its internal circuitry,
reducing total quiescent current to 100
μ
A. When the
converter output begins to fall, the V
C
pin voltage begins
to climb. When the voltage on the V
C
pin climbs back to the
15% load level, the IC returns to normal operation and
switching resumes. An internal clamp on the V
C
pin is set
at 100mV below the output disable threshold, which limits
the negative excursion of the pin voltage, minimizing the
converter output ripple during Burst Mode operation.
During Burst Mode operation, the V
IN
pin current is 20
μ
A
and the V
CC
current is reduced to 80
μ
A. If no external drive
is provided for V
CC
, all V
CC
bias currents originate from the
V
IN
pin, giving a total V
IN
current of 100
μ
A. Burst current
can be reduced further when V
CC
is driven using an output
derived source, as the V
CC
component of V
current is
then reduced by the converter duty cycle ratio.
Start-Up
The following section describes the start-up of the supply
and operation down to 4V once the step-down supply is up
and running. For the protection of the LT3724 and the
switching supply, there are internal undervoltage lockout
(UVLO) circuits with hysteresis on V
IN
, V
CC
and V
BOOST
, as
shown in the Electrical Characteristics table. Start-up and
continuous operation require that all three of these
undervoltage lockout conditions be satisfied because the
TG MOSFET driver is disabled during any UVLO fault
condition. In startup, for most applications, V
CC
is pow-
ered from V
IN
through the high voltage linear regulator of
the LT3724. This requires V
IN
to be high enough to drive
the V
CC
voltage above its undervoltage lockout threshold.
V
CC
, in turn, has to be high enough to charge the BOOST
capacitor through an external diode so that the BOOST
voltage is above its undervoltage lockout threshold. There
is an NPN switch that pulls the SW node to ground each
cycle during the TG power MOSFET off-time, ensuring the
BOOST capacitor is kept fully charged. Once the supply is
up and running, the output voltage of the supply can
backdrive V
CC
through an external diode. Internal circuitry
disables the high voltage regulator to conserve V
IN
supply
current. Output voltages that are too low or too high to
backdrive V
CC
require additional circuitry such as a voltage
doubler or linear regulator. Once V
CC
is backdriven from a
supply other than V
IN
, V
IN
can be reduced to 4V with
normal operation maintained.
OPERATIOU
(Refer to Functional Diagram)
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LT3800EFE | 制造商:Linear Technology 功能描述:Conv DC-DC Single Step Down 4V to 60V 16-Pin TSSOP EP |
| LT3800EFE#PBF | 功能描述:IC REG CTRLR INV PWM CM 16-TSSOP 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 標準包裝: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 |
| LT3800EFE#TRPBF | 功能描述:IC REG CTRLR INV PWM CM 16-TSSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝: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) |
| LT3800EFEPBF | 制造商:Linear Technology 功能描述:DC-DC Converter Step-Down 4-60V TSSOP16 |
| LT3800EFE-PBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:High-Voltage Synchronous Current Mode Step-Down Controller |
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