参数资料
| 型号： | MAX8709BETI+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 21/24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
table. If C3 is 15pF, C4 needs to be 21.2nF to set the
desired maximum RMS secondary voltage to 1600V.
The closest standard value of C4 is 22nF.
The resistor R2 is used to set the VFB DC bias point to
0V. Choose the value of R2 as follows:
range is determined by the transformer secondary leak-
age inductance L, the primary series DC-blocking
capacitor C2, and the secondary parallel resonant
capacitor C3. Since it is difficult to control the trans-
former leakage inductance, the resonant tank design
should be based on the existing secondary leakage
R 2 =
10
2 π × f SW × C 4
inductance of the selected CCFL transformer. The leak-
age inductance values usually have large tolerance
and significant variations among different batches. It is
where f SW is the nominal resonant operating frequency.
Setting the Secondary Current Limit
The MAX8709B limits the secondary current even if the
IFB sense resistor is shorted or transformer secondary
current finds its way to ground without passing through
R1. ISEC monitors the voltage across the sense resistor
best to work directly with transformer vendors on leak-
age inductance requirements. The MAX8709B works
best when the secondary leakage inductance is
between 250mH and 350mH. The series capacitor C2
sets the minimum operating frequency, which is
approximately two times the series resonant peak
frequency. Choose:
R3 connected between the low-voltage terminal of the
transformer secondary winding and ground. Determine
the value of R3 using the following equation:
C 2 ≤
N 2
π 2 × f 2 MIN × L
R 3 =
1 . 25 V
2 × I SEC ( RMS )_ MAX
where f MIN is the minimum operating frequency range.
Parallel capacitor C3 sets the maximum operating fre-
quency, which is also the parallel resonant peak fre-
C 3 ≥
( 4 π × f 2 MAX × L × C 2 ) - N 2
where I SEC(RMS) _ MAX is the desired maximum RMS
transformer secondary current during fault conditions,
and 1.25V is the typical value of the ISEC regulation
point specified in the Electrical Characteristics table.
Transformer Design and Resonant
Component Selection
The transformer is the most important component of the
resonant tank circuit. The first step in designing the
transformer is to determine the transformer turns ratio.
quency. Choose:
C 2
2
The transformer core saturation also needs to be con-
sidered when selecting the operating frequency. The
primary winding should have enough turns to prevent
transformer saturation under all operating conditions.
Use the following expression to calculate the minimum
number of turns (N1) of the primary winding:
The ratio must be high enough to support the CCFL
operating voltage at the minimum supply voltage. The
transformer turns-ratio N can be calculated as follows:
N 1 >
D MAX × V IN ( MAX )
B S × S × f MIN
N =
V LAMP ( RMS )
0 . 9 × V IN ( MIN )
where D MAX is the maximum duty cycle (approximately
0.8) of the high-side switches, V IN(MAX) is the maximum
DC input voltage, B S is the saturation flux density of the
where V LAMP(RMS) is the maximum RMS lamp voltage
in normal operation, and V IN(MIN) is the minimum DC
input voltage.
The next step in the design procedure is to determine
the desired operating frequency range. The MAX8709B
is synchronized to the natural resonant frequency of the
resonant tank. The resonant frequency changes with
operating conditions, such as the input voltage, lamp
impedance, etc. Therefore, the switching frequency
varies over a certain range. To ensure reliable opera-
tion, the resonant frequency range must be within the
operating frequency range specified by the CCFL lamp
transformer manufacturers. As discussed in the
Resonant Operation section, the resonant frequency
core, and S is the minimal cross-section area of the core.
Compensation Design
The CCI capacitor sets the speed of the current loop
that is used during startup, maintaining lamp current
regulation, and during transients caused by changing
the input voltage. The typical CCI value is 0.1μF. Larger
values increase the transient-response delays. Smaller
values speed up transient response, but extremely
small values can cause loop instability.
The CCV capacitor sets the speed of the voltage loop
that affects soft-start and soft-stop during DPWM opera-
tion, and voltage loop stability during startup and open-
lamp conditions. The typical CCV capacitor value is
10nF. Use the smallest value of CCV that gives an
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21
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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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