参数资料
| 型号： | MAX8709BETI+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 13/24页 |
| 文件大小： | 0K |
| 描述： | IC CNTRLR CCFL HI EFF 28-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 类型： | CCFL 控制器 |
| 频率： | 25 ~ 300 kHz |
| 电流 - 电源： | 1.5mA |
| 电流 - 输出： | 500mA |
| 电源电压： | 4.6 V ~ 28 V |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 28-WFQFN 裸露焊盘 |
| 供应商设备封装： | 28-TQFN-EP（5x5） |
| 包装： | 带卷 (TR) |
High-Efficiency CCFL Backlight
Controller with SMBus Interface
C S
1:N
L
4
AC
SOURCE
(a)
C P
CCFL
3
2
R L INCREASING
C' S = S 2
C
N
L
1
0
AC
SOURCE
C P
R L
0
20
40 60
FREQUENCY (kHz)
80
100
(b)
Figure 4. Equivalent Resonant Tank Circuit
Figure 5 shows the frequency response of the resonant
tank’s voltage gain under different load conditions. The
primary series capacitor is 1μF, the secondary parallel
capacitor is 15pF, the transformer turns ratio is 1:93,
and the secondary leakage inductance is 260mH.
Notice there are two peaks, f S and f P , in the frequency
response. The first peak, f S , is the series resonant peak
determined by the reflected series capacitor and the
secondary leakage inductance:
Figure 5. Frequency Response of the Resonant Tank
Once the lamp is ionized, the equivalent load resistance
decreases rapidly and the operating point moves toward
the series resonant peak. The series resonant operation
causes the circuit to behave like a current source.
Current and Voltage Control Loops
(CCI, CCV)
The MAX8709B uses a current loop and a voltage loop
to control the power delivered to the CCFL. The current
loop is the dominant loop in regulating the lamp cur-
f S =
1
2 π LC ' S
rent. The voltage loop limits the transformer secondary
voltage and is active during startup, the DPWM off-
time, and open-lamp fault.
f P =
2 π L
The second peak, f P , is the parallel resonant peak deter-
mined by the reflected series capacitor, the parallel
capacitor, and the secondary leakage inductance:
1
C ' S C P
C ' S + C P
These two frequencies set the lower and upper bound-
aries of resonant operation. When the lamp is off, the
operating point of the resonant tank is close to the paral-
lel resonant peak due to the infinite lamp impedance.
The circuit displays the characteristics of a parallel-
loaded resonant converter, acting like a voltage source
to generate the necessary striking voltage. Theoretically,
the output voltage of the resonant converter keeps
going until the lamp is ionized.
Both the current and the voltage loops use transcon-
ductance error amplifiers for regulation. The AC lamp
current is measured with a sense resistor in series with
the CCFL. The voltage across this resistor is applied to
the IFB input and is internally half-wave rectified. The
current-loop transconductance error amplifier com-
pares the rectified IFB voltage with a 400mV internal
threshold to create an error current. The error current
charges and discharges a capacitor connected
between CCI and ground to generate an error voltage
V CCI . Similarly, the AC voltage across the transformer
secondary winding is measured through a capacitive
voltage-divider. The sense voltage is applied to the
VFB input and is internally half-wave rectified. The volt-
age-loop transconductance error amplifier compares
the rectified VFB voltage with a 500mV internal thresh-
old to create an error current. The error current charges
______________________________________________________________________________________
13
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8709ETI | 功能描述:显示驱动器和控制器 RoHS:否 制造商:Panasonic Electronic Components 工作电源电压:2.7 V to 5.5 V 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:QFN-44 封装:Reel |
| MAX8709ETI+ | 功能描述:显示驱动器和控制器 CCFL Backlight Controller w/SMBus RoHS:否 制造商:Panasonic Electronic Components 工作电源电压:2.7 V to 5.5 V 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:QFN-44 封装:Reel |
| MAX8709ETI+T | 功能描述:显示驱动器和控制器 CCFL Backlight Controller w/SMBus RoHS:否 制造商:Panasonic Electronic Components 工作电源电压:2.7 V to 5.5 V 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:QFN-44 封装:Reel |
| MAX8709ETI-T | 功能描述:显示驱动器和控制器 RoHS:否 制造商:Panasonic Electronic Components 工作电源电压:2.7 V to 5.5 V 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:QFN-44 封装:Reel |
| MAX8709EVKIT | 功能描述:显示开发工具 MAX8709 Eval Kit RoHS:否 制造商:4D Systems 产品:4Display Shields 工具用于评估:?OLED-160-G1, ?OLED-160-G2 接口类型:Serial 工作电源电压:5 V |
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