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| 型号： | MC34848EP |
| 厂商： | Freescale Semiconductor |
| 文件页数： | 32/38页 |
| 文件大小： | 0K |
| 描述： | IC LED DVR BACKLIGHT 8CH 48QFN |
| 产品变化通告： | AMPD Product Discontinuation 12/Dec/2012 |
| 标准包装： | 260 |
| 恒定电流： | 是 |
| 恒定电压： | 是 |
| 拓扑： | PWM，升压（升压） |
| 输出数： | 8 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 频率： | 200kHz ~ 1.2MHz |
| 电源电压： | 2.6 V ~ 3.6 V |
| 输出电压： | 45V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 48-VFQFN 裸露焊盘 |
| 供应商设备封装： | 48-QFN-EP（7x7） |
| 包装： | 托盘 |
| 工作温度： | -40°C ~ 85°C |
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TYPICAL APPLICATIONS
the value of the C COMP2 capacitor, until acquiring an
appropriate stability of the converter. For the previous design
a 56 pF capacitor was used.
G(s) H(s)
Compensated system
G(s)
Boost converter
H(s)
Compensation network
Figure 24. Plotting the Results for the Transconductance Op-amp Based Compensation Example.
SELECTING THE SLEW RATE OF THE SWITCHING
RATE
The SLEW pin is used to limit the slew on the OUT_SW pin
to reduce noise and avoid EMI problems. If the slew rate is
reduced too much, it will reduce the efficiency of the device.
The slew rate can be changed by tying a resistor from the
SLEW pin to GND. The lower the value of this resistor, the
steeper the rising and the falling times of the switching
frequency. The value of this resistor could be within three
different ranges:
? R SLEW < 10 k Ω.
? 10 k Ω ≤ R SLEW < 20 k Ω.
? R SLEW > 20 k Ω.
SELECTING THE CS LOW PASS FILTER TO
REDUCE NOISE.
Since any changes in the PCB layout (track length,
grounding, component connections, etc.) around the
switching FET and the current sense circuitry has an impact
on the PCB parasitics, a low pass RC filter is recommended
to be added at the CS pin for noise reduction.
The selection of this filter should be made based on the
amplitude and frequency of the ringing across the sense
resistor, so the noise can be attenuated properly while the
current sense signal is kept as close as possible to its original
shape (a trapezoid in CCM or a triangle in DCM). The ringing
frequency should be attenuated by 20 dB at least through the
selection of the proper low pass RC filter.
An example: let’s assume that the sense signal (CS)
shows a ringing of 60 MHz, and you want to attenuate it at a
rate of 20 dB per decade. Based on these conditions, the cut-
off frequency (-3.0 dB) of the low pass filter should be set to
6.0 MHz which still allows passing the maximum boost
switching frequency signal of 1.2 MHz. The following formula
is used for calculating the RC components:
f_3 db = 1 / (2 π RC)
It is important to consider that the value of the resistor (R)
should be no higher than 200 ohms, to avoid adding a
significant offset in the CS signal. A resistor of 180 ohms is
selected for this example. The capacitor (C) of the filter is
then selected as follows:
C = 1 / (2 π *180*6E6)
C = 147 pf
Once the filter is added on the CS pin, as shown on figures
20 and 21, measurements should be performed again to
confirm that the noise has been reduced.
34848
Analog Integrated Circuit Device Data
32
Freescale Semiconductor
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MC34848EPR2 | 功能描述:LED照明驱动器 8 CHANNEL 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 |
| MC34849 | 制造商:SPC Multicomp 功能描述:HEADER VERTICAL 16WAY 制造商:SPC Multicomp 功能描述:WIRE-BOARD CONN, RECEPTACLE, 16POS, 3MM; Series:2261(5561); Pitch Spacing:3mm; Contact Termination:Through Hole Vertical; No. of Contacts:16; No. of Rows:2; Connector Mounting:PCB; Gender:Receptacle; Contact Material:Copper Alloy ;RoHS Compliant: Yes |
| MC34851 | 制造商:SPC Multicomp 功能描述:HEADER VERTICAL 18WAY 制造商:SPC Multicomp 功能描述:HEADER, VERTICAL, 18WAY |
| MC34853 | 制造商:SPC Multicomp 功能描述:HEADER R/ANGLE 16WAY 制造商:SPC Multicomp 功能描述:HEADER, R/ANGLE, 16WAY 制造商:SPC Multicomp 功能描述:WIRE-BOARD CONN, RECEPTACLE, 16POS, 3MM; Series:2261(5561); Pitch Spacing:3mm; Contact Termination:Through Hole Right Angle; No. of Contacts:16; No. of Rows:2; Connector Mounting:PCB; Gender:Receptacle; Contact Material:Copper Alloy ;RoHS Compliant: Yes |
| MC34855 | 制造商:SPC Multicomp 功能描述:HEADER R/ANGLE 18WAY 制造商:SPC Multicomp 功能描述:HEADER, R/ANGLE, 18WAY |
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