Maxim MAX9694 TFT LCD电源方案

Maxim 公司的MAX9694提供了四个静态基准电压和用于TFT-LCD灰度修正的14个可编程的基准电压,还具有用于TFT-LCD  VCOM校准的7位数字可变电阻(VCR) 灰度和DVR数值通过I2C接口可编程进寄存器.本文主要介绍了MAX9694的主要特性和MAX9694评估板的主要特性,详细电路图和所用元件清单.

The MAX9694 provides four static voltage references and 14 programmable voltage references for gamma correction in TFT LCDs. The MAX9694 also features a 7-bit digital variable resistor (DVR) for VCOM calibration in TFT LCDs. Gamma and DVR values are programmed into the registers through an I²C interface.

The 14 programmable reference voltages are divided evenly into seven upper and seven lower voltages for the upper and lower gamma curves of LCD column drivers. Each channel has a static 8-bit digital-to-analog converter (DAC) and an isolation buffer to ensure stable reference voltages. This architecture reduces the effects of power-supply noise and kickback current from the source driver chips. Each buffer provides a high peak current to reduce the recovery time of the output voltages when critical levels and patterns are displayed.

The MAX9694 has two features to protect the column drivers during startup. First, the gamma outputs remain in a high-impedance state until the registers are loaded. Second, the four reference buffers ramp up proportionally with the analog supply, which ensures that OUT_REFL_H is always at a lower voltage than OUT_REFU_L.
主要特性:
18 Reference Voltages
7-Bit Digital Variable Resistor (DVR)
Independent DACs with 8-Bit Resolution
20V (max) Operating Voltage
Startup Protection for Column Drivers
Output Swing within 150mV of Rails

应用:
TFT LCDs
MAX9694评估板
The MAX9694 evaluation kit (EV kit) demonstrates the MAX9694 reference voltage generator for gamma correction in TFT-LCD panels, such as those found in highresolution
TVs, high-end monitors, or for general industrial reference voltage generation. The MAX9694 EV kit provides 14 programmable reference voltage outputs (DAC outputs), four static buffered reference voltage outputs (reference outputs), and a 7-bit digital variable reference (DVR) for VCOM voltage calibration.
The EV kit can use a 9V to 20V DC power supply for powering the application circuit.
The EV kit features a USB-to-I2C interface circuit.
Windows  2000/XP- and Windows Vista -compatible software, with a graphical user interface (GUI), is available for exercising the MAX9694 features. The EV kit can also connect to a user-supplied I2C interface circuit for stand-alone MAX9694 operation.
MAX9694评估板主要特性:
14 8-Bit Programmable Reference Voltages (DAC Outputs)
Four Static Buffered Reference Voltages (Reference Outputs)
Programmable VCOM Voltage Calibration
400mA Peak Current on Reference Outputs and DAC Outputs 1, 7, 8, and 14
200mA Peak Current on DAC Outputs 2–6 and 9–13
Peak Output Currents
400mA: 4 DAC Outputs and 4 DAC Reference Outputs
200mA: 10 DAC Outputs
9V to 20V DC Power-Supply Operation
USB-Powered USB-to-I2C Interface Circuit
Windows 2000/XP/Vista (32-Bit)-Compatible Software
Lead-Free and RoHS Compliant
Proven PCB Layout
Fully Assembled and Tested
MAX9694评估板所用元件列表:







图1. MAX9694评估板电路图(1)



图2. MAX9694评估板电路图(2)