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参数资料
| 型号： | LT3751EUFD#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 电源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC20 |
| 封装： | 4 X 5 MM, LEAD FREE, PLASTIC, QFN-20 |
| 文件页数： | 6/34页 |
| 文件大小： | 403K |
| 代理商： | LT3751EUFD#TRPBF |
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LT3751
14
3751fb
OPERATION
Periodic Refresh
When the LT3751 enters regulation, the internal circuitry
deactivates switching when the internal one-shot clock
is high. The clock operates at a 1/20th duty cycle with a
minimum blank time of 1.5μs. This reset pulse is timed to
drastically reduce switching frequency content within the
audio spectrum and is active during all loading conditions.
Each reset pulse guarantees at least one energy cycle. A
minimum load is required to prevent the LT3751 from
entering no-load operation.
Heavy Load Operation
The LT3751 enters peak current mode control at higher
output load conditions. The control loop maximizes the
number of switch cycles between each reset pulse. Since
the control scheme operates in boundary mode, the reso-
nant boundary-mode period changes with varying peak
primary current:
Period
=I
PK LPRI
1
V
TRANS
+
N
V
OUT
and the power output is proportional to the peak primary
current:
P
OUT =
1/ 2 I
PK
1
V
TRANS
+
N
V
OUT
Noise becomes an issue at very low load currents. The
LT3751 remedies this problem by setting the lower peak
current limit to one tenth the maximum level and begins
to employ duty-cycle control.
Light Load Operation
The LT3751 uses duty cycle control to drastically reduce
audible noise in both the transformer (mechanical) and
the ceramic capacitors (piezoelectric effects). Internal
control circuitry forces a one-shot condition at a periodic
rate greater than 20kHz and out of the audio spectrum.
The regulation loop then determines the number of pulses
that are required to maintain the correct output voltage.
Figure 5 shows the use of duty-cycle control.
No-Load Operation
The LT3751 can remain in low noise regulation at very low
loading conditions. Below a certain load current threshold
(Light Load Operation), the output voltage would continue
to increase and a runaway condition could occur. This is
due to the periodic one-shot forced by the periodic refresh
circuitry. By design, the LT3751 has built-in overvoltage
protection associated with the FB pin.
When the FB pin voltage exceeds 1.34V (±20mV), the
LT3751 enters no-load operation. No-load operation does
not reset with the one-shot clock. Instead, the pulse train
is completely load-dependent. These bursts are asynchro-
nous and can contain long periods of inactivity. This allows
regulation at a no-load condition but with the increase of
audible noise and voltage ripple. Note that when operating
with no-load, the output voltage will increase 10% above
the nominal output voltage.
相关PDF资料 |
PDF描述 |
|---|---|
| LT3751EUFD | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC20 |
| LT3751IFE#TRPBF | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO20 |
| LT3782AEFE#TR | SWITCHING CONTROLLER, PDSO28 |
| LT3782AEFE | SWITCHING CONTROLLER, PDSO28 |
| LT3782AEUFD | SWITCHING CONTROLLER, PQCC28 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3751IFE#PBF | 功能描述:IC CTRLR CAP CHARGER 20-TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP（4x4） 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR |
| LT3751IFE#TRPBF | 功能描述:IC CTRLR CAP CHARGER 20-TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP（4x4） 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR |
| LT3751IUFD | 制造商:LINER 制造商全称:Linear Technology 功能描述:Capacitor Charger Controller with Regulation |
| LT3751IUFD#PBF | 功能描述:IC CTRLR CAP CHRGR 4.75V 20-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP（4x4） 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR |
| LT3751IUFD#TRPBF | 功能描述:IC CTRLR CAP CHRGR 4.75V 20-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP（4x4） 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR |
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