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参数资料
| 型号： | MAX8790AETP+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 18/23页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR WHITE BCKLGT 20-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 拓扑： | PWM，升压（升压） |
| 输出数： | 6 |
| 内部驱动器： | 无 |
| 类型 - 主要： | 背光 |
| 类型 - 次要： | 白色 LED |
| 频率： | 1MHz |
| 电源电压： | 4.5 V ~ 5.5 V，5.5 V ~ 26 V |
| 输出电压： | 5V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-WFQFN 裸露焊盘 |
| 供应商设备封装： | 20-TQFN-EP |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 85°C |
Six-String White LED Driver with Active
Current Balancing for LCD Panel Applications
L DCM ( MAX ) = ? 1 ?
?×
The minimum inductor value should be recalculated
after the R S is determined (see the Sense-Resistor
Selection section).
?
?
7 V ?
28 . 72 V + 0 . 4 V ?
( 7 V ) 2 × 0 . 9
= 5 . 8 μ H
Choose an available inductor value from an appropriate
inductor family. Calculate the maximum DC input cur-
rent at the minimum input voltage V IN(MIN), using con-
servation of energy and the expected efficiency at that
operating point ( η MIN ) taken from an appropriate curve
in the Typical Operating Characteristics:
2 × 0 . 825 MHz × 28 . 72 V × 120 mA
An inductance less than L DCM(MAX) is required, so a
4.7μH inductor is chosen. The peak inductor current at
minimum input voltage is calculated as follows:
,
I IN ( DCMAX ) =
I OUT(MAX ) × V OUT
V IN ( MIN ) × η MIN
I PEAK =
120mA × 2 × 28.72V × ( 28.72V + 0.4V ? 7V )
4 . 7 μ H × 0 . 675 MHz × 0 . 9 × ( 28 . 72 V + 0 . 4 V )
= 1 . 35 A
V IN ( MIN ) × ( V OUT ( MAX ) ? V IN ( MIN ) )
L × V OUT ( MAX ) × f OSC
I PEAK IN ( DCMAX ) + RIPPLE
= I
Calculate the ripple current at that operating point and
the peak current required for the inductor:
I RIPPLE =
I
,
2
When DCM operating mode is chosen to minimize the
Sense-Resistor Selection
The detected signal is fed into the step-up converter
control compensation loop through the CS pin.
The MAX8790A’s current-mode step-up converter sens-
es the switch current from CS to GND with an external
resistor, R S . The current-limit sense voltage is a fixed
100mV. The required resistance is calculated based
upon the peak inductor current at the end of the switch
on-time:
inductor value, the calculations are different from that in
the above CCM mode. The maximum inductor value for
DCM mode is calculated by the following equation:
R S <
V CS _ EC + 25.6mV × ( 0.75 ? D MAX )
I PEAK
V OUT ( MAX ) + V DIODE ?
I OUT (max) × 2 × V OUT ( MAX ) × ( V OUT ( MAX ) + V DIODE ? V IN ( MIN ) )
L × f OSC ( MIN ) × η × ( V OUT ( MAX ) + V DIODE )
D MAX =
4 . 7 μ H × 1 . 35 A × 0 . 75 MHz
? V IN ( MIN ) ?
L DCM ( MAX ) = ? 1 ? ?×
?
V IN ( MIN ) 2 × η
2 × f OSC ( MAX ) × V OUT ( MAX ) × I OUT ( MAX )
The peak inductor current in DCM mode is calculated
using the following equation:
I PEAK =
The inductor’s saturation current rating should exceed
I PEAK and the inductor ’s DC current rating should
where 25.6mV is a scale factor from slope compensa-
tion, V CS_EC is the current-sense voltage listed in the
Electrical Characteristics table (85mV), and the D MAX is
the maximum duty cycle at minimum input voltage and
maximum output voltage. In DCM operating mode, it is
calculated by the following equation:
L × I LIM × f OSC
V IN ( MIN )
For the typical operating circuit as Figure 1:
D MAX = = 0 . 68
7 V
exceed I IN(DC,MAX) . For good efficiency, choose an
inductor with less than 0.1 Ω series resistance.
Considering the typical operating circuit, the maximum
R S <
85mV + 25.6mV × ( 0.75 ? 0.68 )
1 . 35 A
= 64 m Ω
load current (I OUT(MAX) ) is 120mA with a 28.72V output
and a minimal input voltage of 7V. Choosing a DCM
operating mode and estimating efficiency of 90% at this
operating point:
Again, R S is calculated as a maximum, so a 56m Ω cur-
rent-sense resistor is chosen.
18
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相关代理商/技术参数 |
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| MAX8790AEVKIT+ | 功能描述:LED 照明开发工具 MAX8790A Eval Kit RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装: |
| MAX8790ETP+ | 功能描述:LED照明驱动器 Six-String White LED Driver RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| MAX8790ETP+T | 功能描述:LED照明驱动器 Six-String White LED Driver RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| MAX8790EVKIT+ | 功能描述:LED 照明开发工具 RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装: |
| MAX8791AGTA+ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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