原标题：On Semi NCV7685 12路60mA LED线性电流驱动解决方案

　　On Semi公司的NCV7685是12路60mA LED线性电流驱动器,具有共通基准的可编恒定电流源.采用PWM技术,器件具有128个可调整的占空比,通过I2C串口可编程,用于每个输出通路.PWM频率有四种不同配置,高达1200Hz.器件可通过I2C总线或独立应用模式和微控制器应用.器件还提供3.3V电压基准,负载电流高达1mA.LED亮度有外接电阻来进行编程.每路有内部电路来检测开路条件,并可选择自动恢复模式.如果一个驱动器在开路条件,所有其它路将根据编程位设定的断开.主要用在汽车仪表盘,后组合灯(RCL),日间运行灯(DRL),雾灯,中央高位刹车灯(CHMSL)阵列,转向灯和其它外部安装应用. 中电网为您整理如下详细资料,本文介绍了NCV7685主要特性,框图和应用框图,以及评估板NCV7685GEVB主要特性,电路图,材料清单和PCB设计图.

　　12 Channels 60 mA LED Linear Current Driver I2C Controllable for Automotive Applications

　　The NCV7685 consists of twelve linear programmable constant current sources with common reference. The part is designed for use in the regulation and control of LED for automotive applications. The NCV7685 allows 128 different duty cycle levels adjustable using pulse width modulation (PWM) independently for each output channel programmable via I2C serial interface. PWM frequency can be chosen in four different configurations up to 1200 Hz. The device can be used with micro−controller applications using the I2C bus or in stand−alone applications where a choice could be done in between 2 different static configuration settings. The IC also provides 3.3 V voltage reference to the application for loads up to 1 mA.

　　LED brightness level is easily programmed using an external resistor. Each channel has an internal circuitry to detect open−load conditions with an optional auto−recovery mode. If one driver is in open−load condition, all other channels could be turned off according to the programmable bit setting.

　　The device is available in small body size SSOP24−EP package.

　　NCV7685主要特性:

　　• 12 Common Current Programmable Sources up to 60 mA

　　• Independent PWM Duty Cycle Control for each Channel via PC

　　• Common PWM Duty Cycle Control via I2C

　　• On−Chip 150, 300, 600 and 1200 Hz PWM

　　• Open LED String Diagnostics

　　• Low Dropout Operation for Pre−Regulator Applications

　　• Single Resistor for Current Set Point

　　• Voltage Reference 3.3 V/1 mA

　　• 8 Bits I2C Interface with CRC8 Error Detection

　　• OTP Bank for Stand−Alone Operation (2 Configurations)

　　• Output Enable Pin

　　• Detection and Protection Against Open Load and Under−Voltage

　　• Over Temperature Detection and Protection

　　• Low Emission with Spread Spectrum Oscillator

　　• NCV Prefix for Automotive and Other Applications Requiring

　　Unique Site and Control Change Requirements; AEC−Q100

　　Qualified and PPAP Capable

　　• SSOP24−EP Packaging

　　NCV7685应用:

　　• Dashboard Applications

　　• Rear Combination Lamps (RCL)

　　• Daytime Running Lights (DRL)

　　• Fog Lights

　　• Center High Mounted Stop Lamps (CHMSL) Arrays

　　• Turn Signal and Other Externally Modulated Applications

　　图1.NCV7685框图

　　图2.NCV7685带微控制器(I2C模式)的应用框图

　　图3.NCV7685不带微控制器(独立模式)的应用框图

　　评估板NCV7685GEVB

　　NCV7685 Twelve Channels LED Linear Current Driver with I2C Interface Evaluation Board

　　The evaluation board demonstrates the Rear Combination Lamp Application with the NCV7685 LED linear current driver. On-board buck converter creates constant voltage of 7.0 V on the top of the LEDs to have lower power dissipation on the device itself. The board contains up to three LEDs in a series for each twelve channels. The amber color of the LEDs emulates TAIL/STOP functionality.

　　The board contain jumper switch where demonstration mode or evaluation mode can be selected. Several different animations can be played without need of computer connection in demonstration mode.

　　NCV7685 has several kinds of the fault detections. Fault detection can be emulated by shorting or opening on-board jumpers. The indication LEDs can inform users about diagnostic and the status of the supplies. More faults and statuses can be read out using PC control software in the evaluation mode configuration.

　　Multiple evaluation boards can be interconnected using I2C communication + DIAG interface. Because default address is the same for every board, the I2C address has to be set independently.

　　评估板NCV7685GEVB主要特性:

　　• Wide Range of Supply Voltage: 8 to 18 V

　　• 3 × 12 Amber LEDs

　　• VSTRING Voltage 7.0 V

　　• VDD Voltage 5.0 V

　　• Nominal LED String Current

　　♦ 10 mA − Nominal Current

　　♦ 50 mA − High Current Set by Jumper

　　• Input CONF1 and CONF2 Switch Selector

　　• LED Open-loads, ISET Short to Ground Emulation Jumpers

　　• Loss of VDD and loss of VS Emulation Jumper

　　• Thermal Shutdown

　　• Global Output Enable Jumper

　　• External I2C Header Connector

　　• Positions for Optional EMC Capacitors

　　• Backward PCB Compatibility with the NCV7684 Device

　　图4.评估板NCV7685GEVB外形图