原标题：TI TPS929120－Q1 FlexWire接口12路汽车LED驱动方案

　　摘要: TI公司的TPS929120-Q1是汽车电子12路40V高边LED驱动器,具有FlexWire接口为每个LED串的单独控制满足日益增长的需求.通过FlexWire串行接口配置,每路能支持模拟调光和PWM调光.内部的电可擦可编程只读存储(EEPROM)允许用户配置设备,以满足系统级安全要求. TPS929120-Q1能控制8位输出电流和12位PWM占空比周期,满足LED开路,短路到地和单个LED短路诊断等多个调整要求.当MCU的连接丢失时,可配置看门狗能自动设定故障状态,而采用可编程的EEPROM, TPS929120-Q1能灵活地设定各中应用方案.器件满足汽车应用的AEC-Q100规范,工作温度–40°C到+125°C,电源电压4.5V-40V,由电阻可设定高达75mA通路电流, 5 mA 到 75 mA时的大电流精度优于±5%,在1mA时的电流精度优于±10%,50mA时的压降500mV,12位单独PWM调光,可编程PWM频率高达20kHz,主要用在汽车外部尾灯,汽车面板指示器和汽车RGB大气照明.本文介绍了TPS929120-Q1主要特性,功能框图和应用电路框图,线性LED驱动器电路图以及评估模块TPS929120EVM主要特性,电路图和PCB设计图.

　　The TPS929120-Q1 includes 12-bit pulse-width modulation (PWM) dimming and offers off-board support – suitable for rear lighting implementations that may span across the entire length of the vehicle, as shown in Figure 2. The TPS929120-Q1 can interface with CAN or LIN communication transceivers, as shown in the digital interface LED driving module reference design, for improved communication robustness.

　　TPS929120-Q1 is an automotive 12-channel LED driver with FlexWire interface to address increasing requirements for individual control of each LED string. Each of its channel can support both analog dimming and pulse-width-modulation (PWM) dimming, configured through its FlexWire serial interface. The internal electrically erasable programmable read-only memory (EEPROM) allows users to configure device in the scenario of communication lost to fulfill system level safety requirements.

　　The FlexWire interface is a robust address-based master-slave interface with flexible baud rate. The interface is based on multi-frame universal asynchronous receiver-transmitter (UART) protocol. The unique synchronization frame of FlexWire reduces system cost by saving external crystal oscillators. It also supports various physical layer with the help of external physical layer transceiver such as CAN or LIN transceivers. The embedded CRC correction is able to ensure robust communication in automotive environments. The FlexWire interface is easily supported by most MCUs in the markets. Each output is a constant current source with individually programmable current output and PWM duty cycle.

　　Each channel various diagnostics feature including LED open-circuit, short-circuit and single-LED short-circuit detection. The on-chip analog-digital convertor (ADC) allows controller to real-time monitor loading conditions.

　　To further increase robustness, the unique fail-safe of the device state machine allows automatic switching to fail-safe states in the case of communication loss, for example, MCU failure. The device supports programming fail-safe settings with user-programmable EEPROM. In fail-safe states, the device supports different configurations if output fails, such as one-fails-all-fail or one-fails-others-on. Each channel can be independently

　　programmed as on or off in fail-safe states. The fail-safe state machine also allows the system to function with pre-programmed EEPROM settings without presence of any controller in the system, also known as stand-alone operation. The fail-safe mode also allows the TPS929120-Q1 to be operating as a general stand-alone device without master processor controlling.

　　The microcontroller can access each of the device through the FlexWire interface. By setting and reading back the registers, the master, which is the microcontroller, has full control over the device and LEDs. All EEPROMs are pre-programmed to default values. TI recommends that users program the EEPROM at the end-of-line for application-specific settings and fail-safe configurations. With increasing demand for animation in automotive lighting, LEDs must be controlled independently.

　　Therefore, LED drivers with digital interfaces are essential to effectively drive pixel-controlled lighting applications. In exterior lighting, multiple lamp functions are typically located on different PCB boards with off-board wires connected to each other.

　　It is difficult for a traditional single-ended interface to meet the strict EMC requirements. By using an industrial-standard CAN physical layer, the UARTbased FlexWire interface of the TPS929120 easily accomplishes long distance off-board communication without impacting EMC.

　　The TPS929120-Q1 is a 12-channel, 40-V high-side LED driver that controls the 8-bit output current and 12-bit PWM duty cycles. The device meets multiple regulation requirements with LED open-circuit, shortto- ground, and single LED short-circuit diagnostics. A configurable watchdog also automatically sets failsafe states when the MCU connection is lost, and, with programmable EEPROM, TPS929120-Q1 can flexibly be set for different application scenarios.

　　TPS929120-Q1主要特性:

　　• AEC-Q100-qualified for automotive applications:

　　– Temperature grade 1: –40°C to +125°C, TA

　　• 12-channel precision high-side current output:

　　– Supply voltage 4.5 V to 40 V

　　– Up to 75 mA channel current set by resistor

　　– 2-Bit global, 6-bit independent current setting

　　– High current accuracy < ±5% at 5 mA to 75 mA

　　– High current accuracy < ±10% at 1 mA

　　– Low voltage drop 500 mV at 50 mA

　　– 12-Bit independent PWM dimming

　　– Programmable PWM frequency up to 20 kHz

　　– Linear and exponential dimming method

　　• FlexWire control interface

　　– Up to 1-MHz clock frequency

　　– Maximum 16 devices on one FlexWire bus

　　– 5-V LDO output to supply CAN transceiver

　　• Diagnostic and protection:

　　– Programmable fail-safe state

　　– LED open-circuit detection

　　– LED short-circuit detection

　　– Single-LED short-circuit diagnostic

　　– Programmable low-supply detection

　　– Open-drain ERR for fault indication

　　– Watchdog and CRC for FlexWire interface

　　– 8-Bit ADC for pin voltage measurement

　　– Overtemperature protection

　　TPS929120-Q1应用:

　　• Automotive exterior rear light

　　• Automotive faceplate indicator

　　• Automotive RGB atmosphere lighting

　　图. TPS929120-Q1功能框图

　　评估模块TPS929120EVM

　　This user's guide describes the setup and use of the TPS929120EVM evaluation module (EVM). This EVM helps the user evaluate the features of the Texas Instruments TPS929120-Q1, which is an automotive 12-channel LED driver with FlexWire interface, to address increasing needs of individual control of each LED string. This document includes hardware setup instructions, software instructions, a schematic diagram, a bill of materials and printed-circuit board layout drawings.

　　评估模块TPS929120EVM包括:

　　• USB2ANY

　　– Ribbon cable

　　– USB cable

　　• TPS929120EVM

　　• TPS929120CANEVM

　　• DB-09 cable

　　图. 评估模块TPS929120EVM套件外形图

　　图. 每有CAN收发器的评估模块TPS929120EVM建立图

　　图. 评估模块TPS929120EVM跳线配置图

　　评估模块TPS929120EVM材料清单: