The mission-critical subsystems must be robust and reliable to ensure driver and passenger safety.

　　關(guān)鍵任務(wù)子系統(tǒng)必須高可靠性，以確保駕駛員和乘客安全。

Circuit blocks in an AV camera subsystems(Fig.2).The camera power supply subsystem requires protection from overcurrents,high energy transients,and ESD.(Littelfuse)

AV攝像機子系統(tǒng)中的電路塊（圖2）。攝像機電源子系統(tǒng)需要保護以防止過電流，高能量瞬變和靜電放電。（Littelfuse）

A two-channel diode array protects both the high and low lines of a CAN transceiver(Fig.3).(Littelfuse)

雙通道二極管陣列保護CAN收發(fā)器線路（圖3）。(Littelfuse)

Figure 4.Recommended ESD protection for an Ethernet transceiver

　　圖4.以太網(wǎng)收發(fā)器的推薦ESD保護

The radar subsystem circuit has both low-noise and conventional DC power supplies(Fig.5)(Littelfuse)

雷達子系統(tǒng)電路同時具有低噪聲和常規(guī)直流電源（圖5）（Littelfuse）

TVS and Schottky diodes give the ADAS communication/control circuit power-surge and reverse-polarity protection(Fig.6)(Littelfuse)

TVS和肖特基二極管為ADAS通信/控制電路提供浪涌和反極性保護（圖6）（Littelfuse）

　　The safety and convenience offered by autonomous vehicles(AVs)cannot be achieved unless the vehicle’s electronic circuits are highly reliable and robust to electrical shocks.Designers can substantially reduce the risk of circuit failures by providing overcurrent protection,transient surge protection,electrostatic discharge(ESD)protection,and reverse polarity protection.Strategies for circuit protection should begin with three mission-critical AV subsystems:camera,radar,and ADAS.

　　除非車輛的電子電路具有高度的可靠性和抗電沖擊能力，否則自動駕駛汽車（AV）所提供的安全性和便利性無法實現(xiàn)。通過提供過電流保護，瞬態(tài)浪涌保護，靜電放電（ESD）保護和反極性保護，設(shè)計人員可以大大降低電路故障的風(fēng)險。電路保護的策略應(yīng)從三個關(guān)鍵任務(wù)的AV子系統(tǒng)開始：攝像機，雷達和ADAS。

Protecting the camera subsystem

保護攝像機子系統(tǒng)

　　In AVs,multiple cameras provide essential forward and backward vision,and work together to provide depth perception and convert visual light through a CCD/CMOS(charge coupled device/complementary metal-oxide semiconductor)image sensor into electronic signals sent to a communication and control circuit.The circuit blocks in a camera subsystem are shown in Fig.2.The key blocks that require protection components are the blocks that connect with external circuitry.

　　在自動駕駛汽車中，多個攝像機提供基本的前向和后向視覺，共同提供深度感知，并通過CCD/CMOS（電荷耦合器件/互補金屬氧化物半導(dǎo)體）圖像傳感器將可見光轉(zhuǎn)換為發(fā)送到通信和控制電路的電子信號。圖2顯示了攝像機子系統(tǒng)中的電路塊。需要保護元件的關(guān)鍵模塊是與外部電路連接的模塊。

　　The camera power supply subsystem requires protection from three potential sources of damage:overcurrents,high energy transients,and ESD.A fuse provides overcurrent protection.Designers can select either a conventional one-time-blow ceramic fuse or a polymer-based,positive temperature coefficient(PPTC)resettable fuse.Both components can have wide temperature ratings for automotive requirements.

　　攝像機電源子系統(tǒng)需要防止三種潛在的損壞來源：過電流、高能量瞬變和靜電放電。熔斷器提供過電流保護。設(shè)計人員可以選擇傳統(tǒng)的一次性陶瓷熔斷器或聚合物正溫度系數(shù)（PPTC）可復(fù)位熔斷器。兩種元件均可滿足汽車要求的寬溫度額定值。

　　The PPTC has the advantage of not needing replacement if an overcurrent condition occurs.This specialized fuse substantially increases in resistance in response to the heat generated by an overcurrent.When the overcurrent is removed,the PPTC recovers to a low resistance and resets the circuit.Both component types have surface-mount packages to save valuable PC board space.

　　PPTC具有在發(fā)生過電流的情況下不需要更換的優(yōu)點。這種專用熔斷器在響應(yīng)過電流產(chǎn)生的熱量時，電阻會顯著增加。消除過電流后，PPTC恢復(fù)到低電阻并重置電路。這兩種元件類型都有表面貼裝封裝，以節(jié)省寶貴的PC板空間。

　　Besides overcurrents,power supply circuits need protection from high energy transients caused by in-vehicle sources such as motors energizing and de-energizing.The circuitry must be capable of withstanding transients defined by ISO Standards 7637 and 16750.Compliant components include transient voltage suppressor(TVS)diodes,which can safely absorb both low-energy transients and high-energy transients as specified in Pulses 1,2,3 and 5 in the above-referenced standards.

　　除了過電流外，電源電路還需要保護，以防車內(nèi)電源（如電機通電和斷電）引起的高能、能量瞬變。電路必須能夠承受ISO標準7637和16750定義的瞬變。兼容元件包括瞬態(tài)電壓抑制器（TVS）二極管，它可以安全地吸收上述參考標準中脈沖1、2、3和5中規(guī)定的低能量瞬態(tài)和高能量瞬態(tài)。

Transceiver solutions

收發(fā)器解決方案

　　To avoid catastrophic failure if the polarity of the voltage to the power supply is accidently reversed,designers can insert a Schottky diode in series with the fuse.While providing reverse polarity protection,the diode’s low forward voltage drop will have a minimal impact on power supply performance.

　　為避免電源電壓極性意外反轉(zhuǎn)時發(fā)生災(zāi)難性故障，設(shè)計人員可以讓保險絲串聯(lián)一個肖特基二極管。在提供反極性保護的同時，二極管的低正向電壓降對電源性能的影響最小。

　　The Controller Area Network(CAN)protocol transceiver needs protection from ESD,fast electrical transients,and other overvoltage transients.Diode arrays have high ESD robustness with models having 30-kV air and 30-kV contact discharge capabilities.These devices are used to help designers meet the ISO 10605 standard for ESD in road vehicles.Furthermore,with the capacitance of about 15 pF and leakage current under 1μA,the diode arrays do not interfere with protocol transmissions.These devices also survive the automotive environment with a temperature operating range of-40°C to+150°C.

　　控制器局域網(wǎng)（CAN）協(xié)議收發(fā)器需要針對靜電放電，快速電氣瞬變和其它過電壓瞬變的保護。二極管陣列具有較高的靜電放電可靠性，其模型具有30 kV空氣和30 kV接觸放電能力。這些器件用于幫助設(shè)計人員滿足道路車輛靜電放電的ISO 10605標準。此外，二極管陣列的電容約為15 pF，漏電流低于1μA，因此不會干擾協(xié)議傳輸。這些器件還可以在-40°C至+150°C的溫度范圍內(nèi)工作，以適應(yīng)汽車環(huán)境。

　　The recommended circuit for protecting a CAN transceiver is shown in Fig.3.A two-channel diode array protects both the high and low lines.A single protection component helps to reduce pick-and-place costs in production.The Ethernet transceiver,like the CAN transceiver,needs ESD protection.Diode arrays and polymer ESD suppressors can provide the necessary protection for the high-speed differential data lines.Models of these diode arrays can provide up to±30 kV ESD protection and can protect a differential line pair in a single package for space savings.An 0402 version is also available as a discrete component to allow for the PC board layout flexibility.

　　保護CAN收發(fā)器的推薦電路如圖3所示。兩通道二極管陣列可以保護CAN總線2根數(shù)據(jù)線。單個保護元件有助于降低生產(chǎn)中的取放成本。像CAN收發(fā)器一樣，以太網(wǎng)收發(fā)器也需要ESD保護。二極管陣列和聚合物ESD抑制器可為高速差分數(shù)據(jù)線提供必要的保護。這些二極管陣列的型號可以提供高達±30 kV的ESD保護，并可以在單個封裝中保護差分線對以節(jié)省空間。0402版本也可作為分立元件提供，以實現(xiàn)PC電路板布局的靈活性。

　　In systems where the capacitance must be absolutely the lowest,the polymer ESD suppressor(AXGD1 series)with 0.04pF can be considered.With capacitance this low,it does not impede 1-Gbit Ethernet transmission rates.An example of the configuration and component that is consistent with recommendations from the OPEN Alliance Ethernet organization is shown in Fig.4.

　　在結(jié)電容必須是絕對最低的系統(tǒng)中，可以考慮使用0.04pF的聚合物靜電抑制器(AXGD1系列)。在電容如此低的情況下，它不會阻礙1千兆位以太網(wǎng)的傳輸速率。圖4中顯示了與OPEN Alliance以太網(wǎng)組織的建議相一致的配置和元件的示例。

　　The most important circuit block is the image sensor block–a bipolar,low-capacitance protection component.This diode can withstand an ESD strike of up to±30 kV and has extremely low leakage current(typical values of under 10 nA)and capacitance around 0.35 pF.For space efficiency,this ESD diode is available in an ultra-small,1.0-mm x 0.5-mm SOD882 package.

　　最重要的電路模塊是圖像傳感器模塊，需要一種雙極性低電容保護元件。該二極管可承受高達±30kV的ESD沖擊，具有極低的泄漏電流(典型值低于10nA)和約0.35pF的電容。為了節(jié)省空間，這種ESD二極管采用1.0 mm x 0.5 mm的超小型SOD882封裝。

　　Protecting the camera subsystem’s four circuit blocks that interface with external circuitry and the external environment will ensure a robust,reliable,visible light detection system.Using the recommended components as close as possible to the circuit inputs will keep extraneous energy from damaging critical circuits.

　　保護攝像機子系統(tǒng)與外部電路和外部環(huán)境相連接的四個電路模塊將確保一個強大、可靠的可見光探測系統(tǒng)。盡可能靠近電路輸入端使用推薦的元件將防止外來能量損壞關(guān)鍵電路。

Protecting the radar subsystem

保護雷達子系統(tǒng)

　　The radar subsystem provides the input for the important forward and side pedestrian detection and collision-avoidance functions.As shown in the Fig.5 block diagram,the radar subsystem circuit has two DC power supplies.A low-noise supply powers the analog radar transmitter and the radar receiver circuit blocks.A conventional power supply powers the logic and communication circuits.Like the camera subsystem power supply,the radar subsystem power supplies need overcurrent protection,transient surge protection,reverse polarity,and ESD protection.

　　雷達子系統(tǒng)為重要的前方和側(cè)面行人檢測和避撞功能提供輸入。如圖5所示，雷達子系統(tǒng)電路有兩個直流電源。低噪聲電源為模擬雷達發(fā)射機和雷達接收機電路模塊供電。傳統(tǒng)電源為邏輯和通信電路供電。與攝像機子系統(tǒng)電源一樣，雷達子系統(tǒng)電源也需要過電流保護、瞬態(tài)浪涌保護、反極性保護和ESD保護。

　　One set of components can protect both supplies from overcurrents and reverse polarity.Again,the designer can select from either a conventional surface-mount fuse or a PPTC resettable fuse.A low forward voltage,Schottky diode,in series with the input line to both supplies will provide reverse polarity protection for the power supplies and for all the radar subsystem circuit blocks.Designers should provide individual supplies with surge protection at the input to each supply.

　　一組元件可以保護兩個電源免受過電流和反極性的影響。同樣，設(shè)計者可以從傳統(tǒng)的表面貼裝保險絲或PPTC可復(fù)位保險絲中進行選擇。低正向電壓肖特基二極管與兩個電源的輸入線串聯(lián)，將為電源和所有雷達子系統(tǒng)電路塊提供反極性保護。設(shè)計人員應(yīng)在每個電源的輸入端為每個電源提供浪涌保護。

　　TVS diodes are the recommended surge protection component.Designers choose the TVS diode based on its transient power rating(400W/600W for low power transients and 1,500W to 7,000W for high power transients)to protect the power supplies.The waveform generator and the analog front-end are part of the radar transmitter and radar receiver,respectively.They are separated from the transmitter and receiver blocks(in Fig.5)since the addition of protection components on the transmitter output and receiver input blocks would alter their transmission and reception impedance.The protection components safeguard as much of the circuits as possible.

　　建議使用TVS二極管作為浪涌保護元件。設(shè)計人員根據(jù)TVS二極管的瞬時額定功率(400W/600W適用于低功率瞬變，1500 W至7000W適用于高功率瞬變)選擇TVS二極管來保護電源。波形發(fā)生器和模擬前端分別是雷達發(fā)射機和雷達接收機的一部分。它們與發(fā)射器和接收器模塊(在圖5中)分開，因為在發(fā)射器輸出和接收器輸入模塊上添加保護元件會改變它們的傳輸和接收阻抗。保護元件可以保護盡可能多的電路。

　　A bipolar component similar to the ESD diode recommended for the image sensor in the camera subsystem will provide the necessary ESD protection.As with the camera subsystem,the radar subsystem transmits its information to the vehicle’s central processing subsystem.Bipolar diode arrays provide ESD protection for both the high and low side of CAN I/O lines.The Ethernet transceiver can use either diode arrays or polymer ESD suppressors to minimize signal distortion and not impact the Ethernet transmission rate.

　　與攝像機子系統(tǒng)中推薦用于圖像傳感器的ESD二極管類似的雙極性元件將提供必要的ESD保護。與攝像機子系統(tǒng)一樣，雷達子系統(tǒng)將其信息傳輸?shù)杰囕v的中央處理子系統(tǒng)。雙極二極管陣列為CAN I/O線的高側(cè)和低側(cè)均提供ESD保護。以太網(wǎng)收發(fā)器可以使用二極管陣列或聚合物ESD抑制器來最大程度地減少信號失真，并且不會影響以太網(wǎng)傳輸速率。

Protecting ADAS communication and control

保護ADAS通信和控制

　　The signal processing,communication,and control subsystem(Fig.6)operate the vehicle.It must be robust,reliable,and failsafe.The circuit must identify other vehicles in traffic,may need to make fast stops due to an animal or person obstructing the vehicle’s path,and needs to have a fail-safe response to a failed sensor.Failsafe firmware is critical but so is hardware that is capable of surviving transient energy strikes.All the circuit blocks that supply information to the controller need protection from ESD.

　　信號處理，通信和控制子系統(tǒng)（圖6）操作車輛。它必須是高可靠性的和無故障的。該電路必須識別出正在行駛的其它車輛，可能由于動物或人擋住車輛的路徑而需要快速停車，并且需要對故障傳感器做出故障安全響應(yīng)。故障安全固件至關(guān)重要，但能夠承受瞬態(tài)能量沖擊的硬件也至關(guān)重要。向控制器提供信息的所有電路模塊都需要防靜電放電保護。

　　The power supply requires overcurrent protection,surge protection,and reverse polarity protection.The fuse for this supply can be located within the module or further upstream in the vehicle’s low voltage junction box.A TVS diode,selected by its surge power rating,provides the necessary surge transient protection.A Schottky diode in series with the power supply input line provides reverse voltage polarity protection.

　　電源需要過電流保護、浪涌保護和反極性保護。該電源的熔斷器可以位于模塊內(nèi)，也可以位于車輛上游的低壓接線盒。通過浪涌功率額定值選擇的TVS二極管可提供必要的浪涌瞬變保護。與電源輸入線串聯(lián)的肖特基二極管可提供反向電壓極性保護。

　　Each communication link requires ESD protection that is designed for the unique performance and configuration of each port.The table below lists the communication protocols used in the ADAS communication and control subsystem and their different data rates.Designers can select from a wide range of diode arrays and polymer ESD suppressors with unique characteristics to protect each communication link without compromising its data rate or its high-to-low voltage differential.

　　每條通信鏈路都需要針對每個端口的獨特性能和配置而設(shè)計的ESD保護。下表列出了ADAS通信和控制子系統(tǒng)中使用的通信協(xié)議及其不同的數(shù)據(jù)速率。設(shè)計人員可以從各種具有獨特特性的二極管陣列和聚合物ESD抑制器中進行選擇，以保護每條通信鏈路，而不會影響其數(shù)據(jù)速率或其高至低電壓差。

　　Any signal lines connecting directly to the DSP circuit block should have ESD protection.Designers can use diode arrays or polymer ESD suppressors that provide bipolar protection for both the high and low signal lines.Designers have a broad range of components that they can use to protect circuitry from the potential stresses noted above.Reliance on AEC-Q qualified components can both accelerate compliance with standards certification bodies while giving the designer confidence that the components will provide the necessary level of protection.

　　任何直接連接到DSP電路模塊的信號線都應(yīng)具有ESD保護。設(shè)計人員可以使用二極管陣列或聚合物ESD抑制器，為差分信號線提供雙極保護。設(shè)計人員有多種元器件可用來保護電路免受上述潛在應(yīng)力的影響。依靠AEC-Q合格元件既可以加速符合認證機構(gòu)的標準，又能讓設(shè)計人員確信元件將提供必要的保護級別。