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參數(shù)資料
| 型號(hào)： | LM3552 |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | LED驅(qū)動(dòng)器 |
| 英文描述： | 1A White LED Driver with Flash Timeout Protection |
| 中文描述： | 第1A白光LED閃光驅(qū)動(dòng)器超時(shí)保護(hù) |
| 文件頁數(shù)： | 10/15頁 |
| 文件大?。?/td> | 756K |
| 代理商： | LM3552 |
Circuit Description
(Continued)
voltage drops to 10.6V(typ), switching will resume. The
LM3551 and LM3552 will go back into OVP if the failure is
still present resulting in a pulsed output condition.
Note:
To disable OVP, ground to OVP pin.
CAUTION: The LM3551 and
LM3552 may be damaged if an OVP condition occurs and OVP is
disabled.
Under-Voltage Protection (UVP)
Both the LM3551 and LM3552 have under-voltage protec-
tion circuitry (UVP). This protects the NMOS power device
during startup and shutdown by preventing operation at
voltages less than the minimum input voltage. The UVP
protection is enabled at 2.48V(typ.) and will not disable until
the input voltage rises above 2.58V(typ.) .
Torch/Flash Pin (T/F)
The
TORCH/FLASH
LM3551/2 is in continuous torch mode, or in flash mode. A
logic ’0’ places the part into torch mode and a logic ’1’ places
the part into flash mode. There are no pull-ups or pull-downs
internally connected to T/F. When placed into torch mode,
FET-T is enabled allowing the current set by R
to flow. In
torch mode, FET-F is not enabled. Flash mode enables both
FET-T and FET-F allowing the sum total of the current set by
the two external resistors, R
T
and R
F
, to flow.
pin
(T/F)
controls
whether
the
Flash Timeout Protection (FTP)
When SD is low(LM3551) or EN is high(LM3552), and T/F is
high, a current is output to an external capacitor, C
FTO
. This
causes the voltage on the capacitor to rise. If the voltage
reaches Vtrip (1.16V(typ)), the timeout circuit forces the
INTERNAL_EN signal to go low, which in turn shuts-off the
low-side torch and flash FETs in addition to disabling the
main power SW FET.At such time, the LED will be turned off.
The part will remain disabled until SD is pulled high
(LM3551) or EN is pulled low (LM3552) and/or T/F is pulled
low. At that point, the part will return to normal operating
mode. The diagram below shows a first pulse which exceeds
the timeout period and internal_EN being driven low. The
second FLASH pulse is shorter than the timeout period and
therefore the voltage on C
never reaches Vtrip. For in-
formation on component selection, please see the
FLASH
TIMEOUT EQUATIONS
below.
20151204
Flash Timeout Protection Diagram
T
FTO
= C
FTO
x (
V
FTO
÷ I
FTO
)
V
FTO
= 1.16V and I
FTO
= 1.4μA
T
FTO
= Desired Timeout Duration
C
FTO
(μF) = T
FTO
(sec.) x 1.21(μA/V)
To disable the timeout function, ground the FTO pin.
Soft-Start
The LM3551 and LM3552 have a soft-start pin that can be
used to limit the inductor inrush current on start-up. The
external SS pin is used to tailor the soft-start for a specific
application but is not required for all applications and can be
left open when not needed. When used, a current source
charges the external soft-start capacitor, C
SS
, forcing the
internal reference to ramp-up at a user determined rate.
Typical Start-Up Times
V
IN
= 3.6V, T
A
= +25C
C
SS
(μF)
Load (mA)
Start-Up Time
(msec.)
3
0.1
Sharp LED
@
75mA Torch
Sharp LED
@
250mA
Flash
Lumiled LED
@
200mA
Torch
Lumiled LED
@
700mA
Flash
Sharp LED
@
75mA Torch
Sharp LED
@
250mA
Flash
Lumiled LED
@
200mA
Torch
Lumiled LED
@
700mA
Flash
Sharp LED
@
75mA Torch
Sharp LED
@
250mA
Flash
Lumiled LED
@
200mA
Torch
Lumiled LED
@
700mA
Flash
8
1.6
6
0.47
12
35
6
35
1.0
25
75
30
70
Application Information
LM3551 AND LM3552 FUNCTIONALITY TRUTH TABLE
SD (LM3551)
or
EN (LM3552)
1
1
0
0
T/F
LM3551 Result LM3552 Result
0
1
0
1
Shut-down
Shut-down
Torch Mode
Flash Mode
Torch Mode
Flash Mode
Shut-down
Shut-down
The LM3551 has a 1.2M
pull-up to V
on SD and the
LM3552 has a 1.2M
pull-down to GND on EN.
CURRENT SET EQUATIONS
The LM3551/2 utilize inline resistors to set the Torch and
Flash LED currents. The Torch-Mode current (continuous)
and the Flash-Mode current (pulsed) are programmed by
placing the appropriately selected resistors between the
feedback pin (FB) and FET-T (torch FET) and FET-F (flash
FET) pins. Torch-mode is set by utilizes the current through
L
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10
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3552SD | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| LM3552SD/NOPB | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| LM3552SDEV | 功能描述:電源管理IC開發(fā)工具 LM3552SD EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| LM3552SDX | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| LM3552SDX/NOPB | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
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