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參數(shù)資料
| 型號： | MAX8729EEI |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 模擬信號調(diào)理 |
| 英文描述： | Constant-Frequency, Half-Bridge CCFL Inverter Controller |
| 中文描述： | SPECIALTY ANALOG CIRCUIT, PDSO28 |
| 封裝： | 0.150 INCH, 0.025 INCH PITCH, MO-137AF, QSOP-28 |
| 文件頁數(shù)： | 18/26頁 |
| 文件大?。?/td> | 395K |
| 代理商： | MAX8729EEI |
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M
Constant-Frequency, Half-Bridge CCFL
Inverter Controller
18
______________________________________________________________________________________
Lamp-Out Protection
For safety, the MAX8729 monitors the lamp-current
feedback (IFB) to detect faulty or open CCFL lamps
and shorted IFB sense resistor. As described in the
Lamp-Current Regulation
section, the voltage on IFB is
internally full-wave rectified. If the rectified IFB voltage
is below 790mV, the MAX8729 charges the TFLT
capacitor with 1μA. The MAX8729 latches off if the volt-
age on TFLT exceeds 4V. Unlike the normal shutdown
mode, the linear regulator output (V
CC
) remains at 5.3V.
Toggling
SHDN
or cycling the input power reactivates
the device.
During the delay period, the current-control loop tries to
maintain the lamp-current regulation by increasing the
high-side MOSFET on-time. Because the lamp imped-
ance is very high when it is open, the transformer sec-
ondary rises as a result of the high-Q factor of the
resonant tank. Once the secondary voltage exceeds
the overvoltage threshold, the MAX8729 turns on a
1.2mA current source that discharges the COMP
capacitor. The on-time of the high-side MOSFET is
reduced, lowering the secondary voltage, as the COMP
voltage decreases. Therefore, the peak voltage of the
transformer secondary winding never exceeds the limit
during the lamp-out delay period.
Primary Overcurrent Protection
The MAX8729 provides cycle-by-cycle primary over-
current protection. A current-sense amplifier monitors
the drain-to-source voltages of both the high-side and
low-side switches when the switches are conducting. If
the voltage exceeds the internal current-limit threshold
(400mV typ), the regulator turns off the high-side switch
at the opposite side of the primary to prevent the trans-
former primary current from increasing further.
Secondary Current Limit (ISEC)
The secondary current limit provides fail-safe protection
in case of short-circuit or leakage from the transformer’s
high-voltage terminal to ground. ISEC monitors the volt-
age across a sense resistor placed between the trans-
former’s low-voltage secondary terminal and ground.
The ISEC voltage is internally half-wave rectified and
continuously compared to the ISEC regulation threshold
(1.25V, typ). Any time the ISEC voltage exceeds the
threshold, a controlled current is drawn from COMP to
reduce the on-time of the bridge’s high-side switches. At
the same time, the MAX8729 charges the TFLT capacitor
with a 126μA current. The MAX8729 latches off when the
voltage on TFLT exceeds 4V. Unlike the normal shut-
down mode, the linear regulator output (V
CC
) remains at
5.3V. Toggling
SHDN
or cycling the input power reacti-
vates the device.
Synchronization in Daisy-Chain Operation
(HFCK, LFCK, PSCK, DPWM)
The MAX8729 supports daisy-chain operation to allow
synchronization and phase shift of multiple MAX8729s.
Up to five MAX8729s can be connected in a daisy-
chain configuration shown in Figure 6. Connecting
CNTL to V
CC
enables the daisy-chain operation and
puts the IC in slave mode.
To synchronize the switching frequency, connect the
HFCK pins of the slave IC and master IC together, and
connect the PSCK pin of the master IC to the HF pin of
ON/OFF
DIMMING
LF
HF
SHDN
CNTL
LFCK
DPWM
PSCK
HFCK
LF
HF
CNTL
LFCK
DPWM
PSCK
HFCK
LF
HF
CNTL
LFCK
DPWM
PSCK
HFCK
LF
HF
CNTL
LFCK
DPWM
PSCK
HFCK
MASTER
SLAVE 1
SLAVE 2
SLAVE 4
V
CC
PS1
PS2
V
CC
PS1
PS2
V
CC
PS1
PS2
V
CC
PS1
PS2
V
CC
SHDN
SHDN
SHDN
Figure 6. Daisy-Chain Operation of Five Controllers
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX8729EEI+ | 功能描述:顯示驅(qū)動器和控制器 Const-f Half-Bridge CCFL Inverter Ctlr RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| MAX8729EEI+T | 功能描述:顯示驅(qū)動器和控制器 Const-f Half-Bridge CCFL Inverter Ctlr RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| MAX8729EEI-T | 功能描述:顯示驅(qū)動器和控制器 RoHS:否 制造商:Panasonic Electronic Components 工作電源電壓:2.7 V to 5.5 V 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-44 封裝:Reel |
| MAX8729EVKIT | 功能描述:電源管理IC開發(fā)工具 MAX8729 Eval Kit RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| MAX872C/D | 功能描述:基準(zhǔn)電壓& 基準(zhǔn)電流 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Voltage References 拓?fù)浣Y(jié)構(gòu):Shunt References 參考類型:Programmable 輸出電壓:1.24 V to 18 V 初始準(zhǔn)確度:0.25 % 平均溫度系數(shù)（典型值）:100 PPM / C 串聯(lián) VREF - 輸入電壓（最大值）: 串聯(lián) VREF - 輸入電壓（最小值）: 分流電流（最大值）:60 mA 最大工作溫度:+ 125 C 封裝 / 箱體:SOT-23-3L 封裝:Reel |
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