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DESIGN NOTEYour Car Deserves the Smartest DriverGiovanni Genna, International Product Marketing Manager, LCD Drivers, NXP Semiconductors, Business Line Interface SolutionsThe PCA8561 is a highly integrated, ultra low power, automotivequalified LCD segment driver housed in the tiny HVQFN32 package,ideal for use with low resolution displays up to 72 icons in multiplexdrive mode 1:4 and where the PCB area and the power consumptionare major concerns.Similarly, in the case where a single LCD driver is used to drive multipledisplays, many connections are required from the LCD driver to at least oneof the displays. Figure 1 shows one NXP LCD driver in a TSSOP56 packagemounted on the PCB of a car climate control unit to drive the two displaysintegrated in the two knobs. The driver is mounted close to one knob so theconnections to the closer display are very short; but the connections to theremote display are very long and take a lot of PCB area.PCA8561The PCA8561 is available in two versions: the AHN version has a 2-line I 2 Cinterface that operates at up to 400kHz, and the BHN version has a 3-lineSPI interface that operates at 3MHz. The PCA8561 is the ideal solution inmany automotive applications since it allows solving many challenges ina simple and cost effective manner, which otherwise would require morecomplicated solutions.Reduce the PCB Area in a Car Climate Control UnitThe PCB design of the car automatic climate control unit faces the challengeto include more components and functionality like multiple temperaturesensors, multiple driving circuitry for more precise and efficient control ofthe heating and cooling systems, multiple displays, more powerful microcontrollers,etc. and, at the same time, to be smaller for more cabin spaceand greater design flexibility.With reference to the LCD driving circuitry, it is preferable to have a standaloneLCD driver mounted close to the display rather than having the LCDdriver integrated in the MCU, which requires many connections from theMCU to the display. Note that the display is typically mounted in theperiphery of the PCB and the MCU is instead mounted in a central positiondue to the multiple connections of all other devices. The PCB area takenby the LCD driver is typically a minor part of the total area taken by theLCD connections.Figure 1: LCD driver used to drive the two displays in the two knobs of a car climate controlThe PCA8561 in the tiny HVQFN32 package (5 x 5mm) can be mountedclose to each knob where the display is integrated; in this case two driversare used but the LCD connections are minimized and only the power suppliesand the interface lines must be routed from the MCU to the displaydrivers, thus simplifying the PCB design and saving much PCB area.Furthermore, some car climate control units implement very small PCBs ineach knob in addition to the main PCB where the MCU is mounted. ThePCA8561 fits in the very small PCB integrated in the knob, while the TSSOPpackage doesn’t, or would require a bigger PCB and then a bigger knob,constraining the cockpit design.Sustain High Operating Temperatures in a Car Climate Control UnitThe increasing complexity of the automatic climate control in automobilescombined with the requirement of smaller size for greater flexibility incabin styling and roominess, have caused problems of excessive heat in theHVAC (heating, ventilation and air conditioning) modules. Some manufacturershave compromised the module size to allow more airflow; someothers have compromised the performance by reducing the electronics inthe module. Further, some car OEMs have started to specify the operatingtemperature of the HVAC module to be +95°C instead of +85°C.The PCA8561 is the ideal solution is such demanding applications. It isAEC-Q100 compliant and covers the operating temperature range from-40°C up to +105°C. Contrary to many LCD segment drivers in themarket, the PCA8561 exceeds customer expectations and allows theclimate control unit to withstand possible excessive heat.141.800.FUTURE.1 • www.FutureElectronics.com
DESIGN NOTEDrive a Small Passive Display in aCar Instrument Cluster Equipped with TFT DisplayThe high-end instrument clusters in vehicles integrate typically a TFT displaybetween the analog gauge clusters. Further, some car OEMs have started toalso request some small customized passive displays integrated inside theanalog clusters to display additional technical information.The microcontrollers tailored for dashboard applications have evolvedto include more features, such as higher CPU performance, increasedmemory size, TFT display control unit, 3D graphic engine, etc., but, as aconsequence, do not include anymore the passive LCD driving circuitry.A dedicated standalone LCD driver is then required to drive the additionalsmall resolution displays inside the clusters.The PCA8561 is the ideal solution for this application due to the small footprint,which allows mounting the driver close to display, the high reliability(AEC-Q100 grade 2 compliant) and the low cost.• It offers the possibility to check if a severe EMI event has occurred, bysimply checking its response by reading the internal registers.• It offers the software reset command and the hardware reset pin; if anEMI failure is detected, the MCU can easily reset the display driver andenable again the display, thus avoiding any stuck condition.Easy Visual InspectionIn a standard HVQFN package, the sides of the terminals consist of bare Cu,which may not be wetted during reflow soldering. Non-wetting failures aredifficult to detect in HVQFN packages.The PCA8561 is assembled in a HVQFN32 package with wettable flanks(see Figure 2) and that makes visual inspection easier and more costeffective. The exposed edge of each terminal contains a small plated cavity,ensuring the solder flows into it and adheres to the side of the terminal.Non-wetting of the sides can be detected easily during the normal opticalinspection.High Immunity to EMIThe increased complexity and electronics in many applications have ledto increased electromagnetic interference (EMI) issues and requirescomponents with higher immunity.When the display is exposed to electrostatic discharge or transients fromswitching electrical motors, it may start to flicker, freeze or go off totally,strongly affecting the human machine interface (HMI).The PCA8561 is ruggedized against EMI and helps enhance the EMC of theapplication module for the following reasons:• Instead of driving the display from the MCU, the PCA8561, thanks to itstiny package, can be mounted close to the display, thus avoiding multiplesensitive connections from the MCU to the display and simplifying thePCB design.• It offers the possibility to switch off the Power-On-Reset (POR) circuitrythrough the Power-On-Reset Enable (PORE) pin. EMI could, in fact,trigger the POR circuitry of the display driver, which puts the chip in resetand switches off the display. If the system is subject to EMI, it is recommendedto switch off the POR functionality.• It specifies ultra low power current consumption; a BOOST function isimplemented to increase the driving capability of the display signals incase of bigger display loads.Figure 2: Wettable flanks on the HVQFN packageThe PCA8561 solves all the most common challenges in automotiveapplications, making it the ideal display driver for low resolutionsegmented LCDs.To buy products or download data, go towww.FutureElectronics.com/FTM1.800.FUTURE.1 • www.FutureElectronics.com15
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