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參數(shù)資料
| 型號： | LM3402MR |
| 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, TSOP-8 |
| 文件頁數(shù)： | 11/24頁 |
| 文件大?。?/td> | 431K |
| 代理商： | LM3402MR |
20192105
FIGURE 1. Comparator and One-Shot
The LM3402/02HV regulators should be operated in contin-
uous 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
Δ
V
, the AC
portion of V
. To determine the average LED current (which
is also the average inductor current) the valley inductor cur-
rent 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 in-
ductor current ripple,
Δ
i
L
:
I
F
= I
L
= I
L-MIN
+ Δ
i
L
/ 2
Detailed information for the calculation of
Δ
i
L
is given in the
Design Considerations section.
MAXIMUM OUTPUT VOLTAGE
The 300 ns minimum off-time limits on the maximum duty cy-
cle of the converter, D
, and in turn ,the maximum output
voltage V
O(MAX)
is determined by the following equations:
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 out-
put voltage are higher, allowing the LM3402/02HV to regulate
output voltages that are nearly equal to input voltage. The
following equation relates switching frequency to maximum
output voltage.
MINIMUM OUTPUT VOLTAGE
The minimum recommended on-time for the LM3402/02HV is
300 ns. This lower limit for t
ON
determines the minimum duty
cycle and output voltage that can be regulated based on input
voltage and switching frequency. The relationship is deter-
mined by the following equation:
11
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3402MR/NOPB | 功能描述:開關(guān)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(guān)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(guān)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(guān)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 |
| LM3403 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Quad Operational Amplifiers |
| LM3403J | 制造商:National Semiconductor 功能描述:3403 NSC'94 S4A1D |
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