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| 型号： | EL7630ICZ-T7A |
| 厂商： | Intersil |
| 文件页数： | 6/7页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR WHITE BCKLGT SC-70-6 |
| 标准包装： | 1 |
| 拓扑： | PWM，升压（升压） |
| 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： | 800kHz ~ 1.8MHz |
| 电源电压： | 2.7 V ~ 5.5 V |
| 输出电压： | 27V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 6-TSSOP，SC-88，SOT-363 |
| 供应商设备封装： | SC-70-6 |
| 包装： | 标准包装 |
| 工作温度： | -40°C ~ 85°C |
| 产品目录页面： | 1242 (CN2011-ZH PDF) |
| 其它名称： | EL7630ICZ-T7ADKR |
EL7630
L1
Components Selection
V IN
2.7V~5.5V
C1
1μF
22μH
VDD LX
EL7630
ENAB FB
D1
R1
LEDs
C2
0.22μF
The input capacitance is normally 0.22μF~4.7μF and the
output capacitor is 0.22μF~1μF. X5R or X7R type of ceramic
capacitor with the correct voltage rating is recommended.
The output capacitor value will affect PWM dimming
performance. For lower output capacitor values, the range of
PWM dimming is wider than for higher values of output
OFF/ON
GND
R2
R SET
4.75 ?
capacitor.
When choosing an inductor, make sure the inductor can
V Dim = V FB + ( V FB – I LED ? R SET ) ? -------
R 1
I LED ? V OUT
0.8 ? V IN
I LPK = I LAVG + --- ? ? I L
2
? I L = ---------------------------------------------------
V IN ? ( V OUT – V IN )
L ? V OUT ? f OSC
DIMMING SIGNAL
FIGURE 9. ANALOG DIMMING CONTROL APPLICATION
CIRCUIT
For a required LED current I LED and chosen values of R 1
and R 2 , the dimming DC voltage V Dim can be expressed as:
R 2
(EQ. 5)
It is clear that as the required LED current I LED is closed to
the rate current V FB /R SET , V Dim is closed to V FB . As the
required LED current is lower than the rate current, the
dimming DC voltage V Dim is increased in R 2 /R 1 factor.
Open-Voltage Protection
In some applications, it is possible that the output is
opened, e.g. when the LEDs are disconnected from the
circuit or the LEDs fail. In this case the feedback voltage
will be zero. The EL7630 will then switch to a high duty
cycle resulting in a high output voltage, which may cause
the LX pin voltage to exceed its maximum 27V rating. To
implement overvoltage protection, a zener diode Dz and a
resistor R 1 can be used at the output and FB pin to limit the
voltage on the LX pin as shown in Figure 10. It is clear that
as the zener is turned on, due to the overvoltage, the zener
diode’s current will set up a voltage on R 1 and R SET and this
voltage is applied on FB pin as the feedback node. This
feedback will prevent the output from reaching the
overvoltage condition. In the overvoltage protection circuit
design, the zener voltage should be larger than the
maximum forward voltage of the LED string.
handle the average and peak currents given by the following
formulas (80% efficiency assumed):
I LAVG = --------------------------------- (EQ. 6)
1
(EQ. 7)
(EQ. 8)
Where:
? ? I L is the peak-to-peak inductor current ripple in Ampere
? L inductance in H.
? f OSC switching frequency, typically 1.2MHz
The boost inductor can be chosen in a wide range of
inductance (10μH~82μH). For 10μH inductor value, the
boost inductor current will be in discontinuous mode. As the
inductor value decreases further, the ripple of the boost
inductor current is increased and can even trigger
overcurrent protection. For high boost inductor value, the
boost inductor current will be in continuous mode. For
general boost converter, as the converter operates in
continuous mode, there is right half plane zero (RHPZ). If
RHPZ frequency is less than or close to the control loop
crossover frequency, there is a stability issue. In EL7630, the
compensation network is well designed and there is no
RHPZ stability issue even if the inductor value is over 82μH.
For the same series of inductors, a lower inductance has
lower DC resistance (DCR), which causes less conducting
loss, but higher peak to peak current variation, which
L1
22μH
D1
generates more RMS current loss. Figure 11 shows the
efficiency of the demo board with different LED load for a
V IN
2.7V~5.5V
VDD
LX
LEDs
specific series of inductor.
The diode used should be a schottky type with minimum
D ? ? 2 ? I LAVG + --- ? ? I L ?
I RMS =
?
?
6
C1
1μF
OFF/ON
EL7630
ENAB FB
GND
Dz
R1
R SET
4.75 ?
C2
0.22μF
reverse voltage of 28V. The diode’s peak current is the same
as the inductor ’s peak current. The schottky RMS current is:
2 1 2
(EQ. 9)
FIGURE 10. LED DRIVER WITH OVERVOLTAGE
PROTECTION CIRCUIT
6
FN7371.1
February 22, 2006
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相关代理商/技术参数 |
参数描述 |
|---|---|
| EL7630IWTZ | 制造商:Intersil Corporation 功能描述:LED DRVR 6SEGMENT 2.7V TO 5.5V 5PIN TSOT - Bulk |
| EL7630IWTZ-EVAL | 功能描述:LED 照明开发工具 EL7630IWTZ-EVAL DEMO BRD 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: |
| EL7630IWTZ-T7 | 功能描述:LED显示驱动器 EL7630IWTZ WHT LED BOOSTG RoHS:否 制造商:Micrel 数位数量:5 片段数量: 安装风格:SMD/SMT 封装 / 箱体:PLCC-44 工作电源电压:4.75 V to 11 V 最大电源电流:10 mA 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装:Tube |
| EL7630IWTZ-T7A | 功能描述:LED显示驱动器 EL7630IWTZ WHT LED BOOSTG RoHS:否 制造商:Micrel 数位数量:5 片段数量: 安装风格:SMD/SMT 封装 / 箱体:PLCC-44 工作电源电压:4.75 V to 11 V 最大电源电流:10 mA 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装:Tube |
| EL7640 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:TFT-LCD DC/DC with Integrated Amplifiers |
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