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参数资料
| 型号： | MAX8790AETP+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 14/23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
Open-Current Source Protection
The MAX8790A step-up converter output voltage is reg-
ulated according to the minimum value of the enable
Average Error Per LED =
5.150V
N
FB_ voltages. If an individual LED string is open, the
respective FB_ is pulled down to near ground. In this sit-
uation, the step-up converter output voltage increases
but is clamped to a level set with the OV feedback
input. When this elevated output voltage is applied to
the undamaged strings, excessive voltage drop devel-
ops across the FB_ pins. If the resulting HVC signal
exceeds V CC + 0.6V for greater than 65ms, the fault
latch is triggered to protect the circuit.
LED-Short and String Mismatch Protection
Normally, white LEDs have variations in forward-voltage
drop of 3.1V to 3.6V. The MAX8790A can tolerate slight
mismatches between LED strings. When the sum of the
LED forward voltages creates a mismatch in the strings
so the HVC signal exceeds V CC + 0.6V for greater than
65ms, the fault latch is triggered in much the same way
as the circuit responds to open string faults. Similar pro-
tection is activated when an LED is shorted.
The larger the number of series-connected LEDs (N),
the smaller the tolerable mismatch between LEDs:
∑ Error < V CC + 0 . 6 V ? V SAT
N
V SAT ≈ 450mV and V CC = 5V
∑ Error < 5 . 150 V
N
For N = 8, the average error per LED = 644mV.
For N = 10, the average error per LED = 510mV.
The larger the total mismatch, the larger the voltage
drop required across each current source to correct for
the error, and therefore the larger the dissipation within
the MAX8790A.
Dimming Control
The MAX8790A features both analog and digital dim-
ming control. Analog dimming can provide potentially
higher converter efficiency because of low voltage drop
across each WLED when the current is low. Digital dim-
ming (DPWM) provides less WLED color distortion
since the WLED current is held at full scale when the
WLED is on.
The MAX8790A’s dimming control circuit consists of a
PLL, a digital comparator, and a DAC. The controller
provides 100:1 dimming range through either analog or
digital control methods. Both methods translate the
duty cycle of the BRT input into a control signal for the
LED current sources. In analog dimming mode, the cur-
rent-source outputs are DC and the BRT duty cycle
(12.5% < D BRT < 100%) modulates the amplitude of
the currents. For D BRT < 12.5%, the LED current is digi-
tally modulated to reduce the average LED current
down to 1% of full scale. The PLL detects the BRT fre-
quency and phase, and adjusts the current-source
amplitude and duty cycle synchronously (see Figure 4).
D=
t ON
t BRT
ANALOG DIMMING MODE
BRT
D = 50%
t ON
D = 30%
D = 12.5%
D = 6.25%
t BRT
I LEDMAX
I LED
0A
Figure 4. LED Current Control Using Analog Dimming Mode
14
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PDF描述 |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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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