参数资料
| 型号： | MAX8722CEEG+ |
| 厂商： | Maxim Integrated |
| 文件页数： | 19/21页 |
| 文件大小： | 0K |
| 描述： | IC CCFL BACKLIGHT CTRL 24-QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| 类型： | CCFL 控制器 |
| 频率： | 30 ~ 80 kHz |
| 电流 - 电源： | 1mA |
| 电流 - 输出： | 300mA |
| 电源电压： | 4.6 V ~ 28 V |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 24-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 24-QSOP |
| 包装： | 管件 |
Low-Cost CCFL Backlight Controller
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:
Layout Guidelines
Careful PC board (PCB) layout is important to achieve
stable operation. The high-voltage section and the
switching section of the circuit require particular atten-
4 × π 2 × f MIN
C 2 ≤
N 2
2
× L
tion. The high-voltage sections of the layout need to be
well separated from the control circuit. Most layouts for
single-lamp notebook displays are constrained to long
and narrow form factors, so this separation occurs natu-
where f MIN is the minimum operating frequency range.
In the circuit of Figure 1, the transformer’s turns ratio is
93 and its secondary leakage inductance is approxi-
mately 300mH. To set the minimum operating frequen-
cy to 45kHz, use 1μF for C2.
The parallel capacitor C3 sets the maximum operating
frequency, which is also the parallel resonant peak fre-
quency. Choose C3 with the following equation:
rally. Follow these guidelines for good PCB layout:
1) Keep the high-current paths short and wide, espe-
cially at the ground terminals. This is essential for
stable, jitter-free operation and high efficiency.
2) Use a star-ground configuration for power and ana-
log grounds. The power and analog grounds should
be completely isolated—meeting only at the center
of the star. The center should be placed at the ana-
C 3 ≥
( 4 π
2
× f MAX
2
C 2
× L × C 2 ) ? N 2
log ground pin (GND). Using separate copper
islands for these grounds may simplify this task.
Quiet analog ground is used for V CC , COMP, FREQ,
TFLT, and ILIM (if a resistive voltage-divider is
In the circuit of Figure 1, to set the maximum operating
frequency to 65kHz, use 18pF for C3.
The transformer core saturation should also be consid-
ered when selecting the operating frequency. The pri-
mary 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:
used).
3) Route high-speed switching nodes away from sen-
sitive analog areas (V CC , COMP, FREQ, TFLT, and
ILIM). Make all pin-strap control input connections
(ILIM, etc.) to analog ground or V CC rather than
power ground or V DD .
4) Mount the decoupling capacitor from V CC to GND
as close as possible to the IC with dedicated traces
N 1 >
D MAX × V IN ( MAX )
B S × S × f MIN
that are not shared with other signal paths.
5) The current-sense paths for LX1 and LX2 to GND
must be made using Kelvin sense connections to
guarantee the current-limit accuracy.
where D MAX is the maximum duty cycle (approximately
0.4) of the high-side switches, V IN(MAX) is the maximum
DC input voltage, B S is the saturation flux density of the
core, and S is the minimal cross-section area of the core.
COMP Capacitor Selection
The COMP capacitor sets the speed of the current loop
that is used during startup, while maintaining lamp cur-
rent regulation, and during transients caused by chang-
ing the input voltage. The typical COMP capacitor value
is 0.01μF. Larger values increase the transient-response
delays. Smaller values speed up transient response, but
extremely small values can cause loop instability.
Other Components
The external bootstrap circuits formed by capacitors C5
and C6 in Figure 1 power the high-side MOSFET drivers.
Connect V DD to BST1/BST2 and couple BST1/BST2 to
LX1/LX2 through C5 and C6. C5 = C6 = 0.1μF or greater.
6) Ensure the feedback connections are short and
direct. To the extent possible, IFB, VFB, and ISEC
connections should be far away from the high-volt-
age traces and the transformer.
7) To the extent possible, high-voltage trace clearance
on the transformer’s secondary should be widely
separated. The high-voltage traces should also be
separated from adjacent ground planes to prevent
lossy capacitive coupling.
8) The traces to the capacitive voltage-divider on the
transformer’s secondary need to be widely separated
to prevent arcing. Moving these traces to opposite
sides of the board can be beneficial in some cases.
______________________________________________________________________________________
19
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相关代理商/技术参数 |
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|---|---|
| MAX8722CEEG+ | 功能描述:显示驱动器和控制器 CCFL Backlight Controller 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 |
| MAX8722CEEG+T | 功能描述:显示驱动器和控制器 CCFL Backlight Controller 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 |
| MAX8722EEG | 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 |
| MAX8722EEG+ | 功能描述:显示驱动器和控制器 CCFL Backlight Controller 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 |
| MAX8722EEG+T | 功能描述:显示驱动器和控制器 CCFL Backlight Controller 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 |
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