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| 型号： | ISL97678IRZ |
| 厂商： | Intersil |
| 文件页数： | 11/18页 |
| 文件大小： | 0K |
| 描述： | IC LED DVR PWM DIMMING 8CH 32QFN |
| 标准包装： | 60 |
| 拓扑： | 线性（LDO），PWM，升压（升压） |
| 输出数： | 8 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 类型 - 次要： | RGB，白色 LED |
| 频率： | 500kHz ~ 1.5MHz |
| 电源电压： | 4.75 V ~ 26 V |
| 输出电压： | 45V |
| 安装类型： | * |
| 封装/外壳： | * |
| 供应商设备封装： | * |
| 包装： | * |
| 工作温度： | -40°C ~ 85°C |
ISL97678
Typical Performance Curves (Continued)
V O (20V/DIV)
EN (5V/DIV)
I IN (1A/DIV)
I LED (50mA/DIV)
FIGURE 23. DISABLE PROFILE
Theory of Operation
PWM Boost Converter
The current mode PWM boost converter produces the
minimal voltage needed to enable the LED string with the
highest forward voltage drop to run at the programmed
current. The ISL97678 employs current mode control
boost architecture that has a fast current sense loop and
a slow voltage feedback loop. Such architecture achieves
.
a fast transient response that is essential for the
notebook backlight application where the power can be
several Li-ion cell batteries or instantly change to an
AC/DC adapter without rendering a noticeable visual
RSET
+
-
REF
+
-
nuisance. The number of LEDs that can be driven by
ISL97678 depends on the type of LED chosen in the
application. The ISL97678 is capable of boosting up to
45V and drive 8 channels of LEDs at maximum of 45mA
PWM DIMMING
+
-
per channel.
Current Matching and Current Accuracy
Each channel of the LED current is regulated by the
current source circuit, as shown in Figure 24.
The LED peak current is set by translating the R SET
current to the output with a scaling factor of 707.9/R SET .
The source terminals of the current source MOSFETs are
designed to run at 500mV to optimize power loss versus
accuracy requirements. The sources of errors of the
channel-to-channel current matching come from the
op amps offset, internal layout, reference, and current
source resistors. These parameters are optimized for
current matching and absolute current accuracy.
However, the absolute accuracy is additionally
determined by the external R SET . A 0.1% tolerance
resistor is recommended.
11
FIGURE 24. SIMPLIFIED CURRENT SOURCE CIRCUIT
Dynamic Headroom Control
The ISL97678 features a proprietary Dynamic Headroom
Control circuit that detects the highest forward voltage
string or effectively the lowest voltage from any of the
CH pins. When this lowest I IN voltage is lower than the
short circuit threshold, V SC , such voltage will be used as
the feedback signal for the boost regulator. The boost
makes the output to the correct level such that the
lowest CH pin is at the target headroom voltage. Since all
LED strings are connected to the same output voltage,
the other CH pins will have a higher voltage, but the
regulated current source circuit on each channel will
ensure that each channel has the same programmed
current. The output voltage will regulate cycle-by-cycle
and is always referenced to the highest forward voltage
string in the architecture.
FN6998.1
November 5, 2009
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| ISL97678IRZ-T | 功能描述:IC LED DVR PWM DIMMING 8CH 32QFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 恒定电流:- 恒定电压:- 拓扑:升压（升压），切换式电容器（充电泵） 输出数:1 内部驱动器:是 类型 - 主要:背光 类型 - 次要:白色 LED 频率:625kHz ~ 875kHz 电源电压:2.7 V ~ 5.3 V 输出电压:5V 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽） 供应商设备封装:10-µMAX 包装:带卷 (TR) 工作温度:-40°C ~ 85°C |
| ISL97678IRZ-TK | 功能描述:IC LED DVR PWM DIMMING 8CH 32QFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 恒定电流:- 恒定电压:- 拓扑:升压（升压），切换式电容器（充电泵） 输出数:1 内部驱动器:是 类型 - 主要:背光 类型 - 次要:白色 LED 频率:625kHz ~ 875kHz 电源电压:2.7 V ~ 5.3 V 输出电压:5V 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽） 供应商设备封装:10-µMAX 包装:带卷 (TR) 工作温度:-40°C ~ 85°C |
| ISL97682IRTZ | 功能描述:IC LED DVR PWM CTRL 2CH 16TQFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 恒定电流:- 恒定电压:- 拓扑:升压（升压），切换式电容器（充电泵） 输出数:1 内部驱动器:是 类型 - 主要:背光 类型 - 次要:白色 LED 频率:625kHz ~ 875kHz 电源电压:2.7 V ~ 5.3 V 输出电压:5V 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽） 供应商设备封装:10-µMAX 包装:带卷 (TR) 工作温度:-40°C ~ 85°C |
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| ISL97682IRTZR5509 | 功能描述:LED照明驱动器 1 Channel LED Drivers, 16LD TQFN 3X3 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 |
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