参数资料
| 型号： | MAX8709BETI+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 15/24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
POR and UVLO
The MAX8709B includes power-on-reset (POR) and
undervoltage-lockout (UVLO) circuits. The POR resets all
internal registers such as DAC outputs, fault latches,
and all SMBus registers. POR occurs when V CC is below
1.5V. The SMBus input logic thresholds are only guaran-
teed to meet electrical characteristic limits for V CC as
low as 3.5V, but the interface continues to function down
to the POR threshold.
The UVLO is activated and disables both high-side and
low-side switch drivers when V CC is below 4.2V (typ).
Low-Power Shutdown (SUS)
When the MAX8709B is placed in shutdown, all functions
of the IC are turned off except for the 5.3V linear regulator
that powers all internal registers and the SMBus inter-
face. The SMBus interface is accessible in shutdown. In
shutdown, the linear-regulator output voltage drops to
about 4.5V and the supply current is 6μA (typ), which is
the required power to maintain all internal register states.
While in shutdown, lamp-out detection and short-circuit
detection latches are reset. The device can be placed
into shutdown either by writing to the shutdown-mode
register or pulling SUS low.
Lamp-Out Protection
For safety, the MAX8709B monitors the lamp-current
feedback (IFB) to detect faulty or open CCFL tubes and
secondary short circuits in the lamp and IFB sense
resistor. If the voltage on IFB is continuously below 30%
of the LOT voltage for greater than 1.22s (typ), the
MAX8709B latches off the full bridge. Unlike the normal
shutdown mode, the linear-regulator output (V CC )
remains at 5.3V. Toggling SUS or cycling the input
power reactivates the device.
During the 1.22s delay, V CCI slowly rises, increasing
t ON in an attempt to maintain lamp current regulation.
As V CCI rises, V CCV rises with it until the secondary
voltage reaches its preset limit. At this point, V CCV
stops and limits the secondary voltage by limiting t ON .
Because V CCV is limited to 150mV above V CCI , the volt-
age control loop is able to quickly limit the secondary
voltage. Without this clamping feature, the transformer
voltage overshoots to dangerous levels because V CCV
takes time to slew down from its supply rail.
Primary Overcurrent Protection (ILIM)
The MAX8709B senses primary current in each switching
cycle. When the regulator turns on the low-side MOSFET,
a comparator monitors the voltage drop from LX_ to GND.
If the voltage exceeds the current-limit threshold, the reg-
ulator turns off the high-side switch at the opposite side of
the primary to prevent the transformer primary current
from increasing further.
The current-limit threshold can be adjusted using the
ILIM input. Connect a resistive voltage-divider between
REF or V CC and GND with the midpoint connected to
ILIM. The current-limit threshold measured between
LX_ and GND is 1/5 the voltage at ILIM. The ILIM
adjustment range is 0 to 3V. Connect ILIM to V CC to
select the default current-limit threshold of 0.2V.
Secondary Current Limit (ISEC)
The secondary current limit provides fail-safe current
limiting in case a failure, such as a short circuit or leak-
age from the lamp high-voltage terminal to ground, pre-
vents the CCI current control loop from functioning
properly. ISEC monitors the voltage across a sense
resistor placed between the transformer’s low-voltage
secondary terminal and ground. The ISEC voltage is
internally half-wave rectified and continuously com-
pared to the ISEC regulation threshold (1.25V typ). Any
time the ISEC voltage exceeds the threshold, a con-
trolled current is drawn from CCI to reduce the on-time
of the bridge’s high-side switches.
Reference Output (REF)
The reference output is nominally 2V, and can source at
least 40μA (see the Typical Operating Characteristics ).
Bypass REF with a 0.22μF ceramic capacitor connected
between REF and GND.
Linear-Regulator Output (V CC )
The internal linear regulator steps down the DC input volt-
age to 5.3V (typ). The linear regulator supplies power to
the internal control circuitry of the MAX8709B and can
also be used to power the MOSFET drivers by connect-
ing V CC directly to V DD . The V CC voltage drops to 4.5V in
shutdown.
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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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