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參數(shù)資料
| 型號： | LM3402MMX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.5A Constant Current Buck Regulator for Driving High Power LEDs |
| 中文描述： | 0.94 A SWITCHING REGULATOR, PDSO8 |
| 封裝： | PLASTIC, MSOP-8 |
| 文件頁數(shù)： | 10/22頁 |
| 文件大?。?/td> | 840K |
| 代理商： | LM3402MMX |
Application Information
(Continued)
The LM3402/02HV regulators should be operated in continu-
ous conduction mode (CCM), where inductor current stays
positive throughout the switching cycle. During steady-state
operationin the CCM, the converter maintains a constant
switching frequency, which can be selected using the follow-
ing equation:
V
F
= forward voltage of each LED, n = number of LEDs in
series
AVERAGE LED CURRENT ACCURACY
The COT architecture regulates the valley of
V
, the AC
portion of V
. To determine the average LED current
(which is also the average inductor current) the valley induc-
tor current is calculated using the following expression:
In this equation t
represents the propagation delay of the
CS comparator, and is approximately 220 ns. The average
inductor/LED current is equal to I
L-MIN
plus one-half of the
inductor current ripple,
i
L
:
I
F
= I
L
= I
L-MIN
+
i
L
/ 2
Detailed information for the calculation of
i
L
is given in the
Design Considerations section.
MAXIMUM OUTPUT VOLTAGE
The 300 ns minimum off-time limits on the maximum duty
cycle of the converter, D
MAX
, and in turn ,the maximum
output voltage V
O(MAX)
is determined by the following equa-
tions:
The maximum number of LEDs, n
, that can be placed in
a single series string is governed by V
and the maxi-
mum forward voltage of the LEDs used, V
F(MAX)
, using the
expression:
At low switching frequency the maximum duty cycle and
output voltage are higher, allowing the LM3402/02HV to
regulate output voltages that are nearly equal to input volt-
age. The following equation relates switching frequency to
maximum output voltage.
20192105
FIGURE 1. Comparator and One-Shot
L
www.national.com
10
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM3402MMX/NOPB | 功能描述:開關變換器、穩(wěn)壓器與控制器 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| LM3402MR | 制造商:Texas Instruments 功能描述:Conv DC-DC Single Step Down 6V to 42V 8-Pin PSOP EP Rail |
| LM3402MR/NOPB | 功能描述:開關變換器、穩(wěn)壓器與控制器 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| LM3402MRX | 制造商:Texas Instruments 功能描述:Conv DC-DC Single Step Down 6V to 42V 8-Pin HSOP EP T/R |
| LM3402MRX/NOPB | 功能描述:開關變換器、穩(wěn)壓器與控制器 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
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