NXP – PCA8561: Your Car Deserves the Smartest Driver

The PCA8561 is a highly integrated, ultra low power, automotive qualified LCD segment driver housed in the tiny HVQFN32 package, ideal for use with low resolution displays up to 72 icons in multiplex drive mode 1:4 and where the PCB area and the power consumption are major concerns.

The PCA8561 is available in two versions: the AHN version has a 2-line I2C interface that operates at up to 400kHz, and the BHN version has a 3-line SPI interface that operates at 3MHz. The PCA8561 is the ideal solution in many automotive applications since it allows solving many challenges in a simple and cost effective manner, which otherwise would require more complicated solutions.

Reduce the PCB Area in a Car Climate Control Unit
The PCB design of the car automatic climate control unit faces the challenge to include more components and functionality like multiple temperature sensors, multiple driving circuitry for more precise and efficient control of the heating and cooling systems, multiple displays, more powerful microcontrollers, etc. and, at the same time, to be smaller for more cabin space and greater design flexibility.

With reference to the LCD driving circuitry, it is preferable to have a standalone LCD driver mounted close to the display rather than having the LCD driver integrated in the MCU, which requires many connections from the MCU to the display. Note that the display is typically mounted in the periphery of the PCB and the MCU is instead mounted in a central position due to the multiple connections of all other devices. The PCB area taken by the LCD driver is typically a minor part of the total area taken by the LCD connections.

Similarly, in the case where a single LCD driver is used to drive multiple displays, many connections are required from the LCD driver to at least one of the displays. Figure 1 shows one NXP LCD driver in a TSSOP56 package mounted on the PCB of a car climate control unit to drive the two displays integrated in the two knobs. The driver is mounted close to one knob so the connections to the closer display are very short; but the connections to the remote display are very long and take a lot of PCB area.

Figure 1: LCD driver used to drive the two displays in the two knobs of a car climate control

Figure 1: LCD driver used to drive the two displays in the two knobs of a car climate control

The PCA8561 in the tiny HVQFN32 package (5 x 5mm) can be mounted close to each knob where the display is integrated; in this case two drivers are used but the LCD connections are minimized and only the power supplies and the interface lines must be routed from the MCU to the display drivers, thus simplifying the PCB design and saving much PCB area.

Furthermore, some car climate control units implement very small PCBs in each knob in addition to the main PCB where the MCU is mounted. The PCA8561 fits in the very small PCB integrated in the knob, while the TSSOP package 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 Unit
The increasing complexity of the automatic climate control in automobiles combined with the requirement of smaller size for greater flexibility in cabin styling and roominess, have caused problems of excessive heat in the HVAC (heating, ventilation and air conditioning) modules. Some manufacturers have compromised the module size to allow more airflow; some others have compromised the performance by reducing the electronics in the module. Further, some car OEMs have started to specify the operating temperature of the HVAC module to be +95°C instead of +85°C.

The PCA8561 is the ideal solution is such demanding applications. It is AEC-Q100 compliant and covers the operating temperature range from -40°C up to +105°C. Contrary to many LCD segment drivers in the market, the PCA8561 exceeds customer expectations and allows the climate control unit to withstand possible excessive heat.

Drive a Small Passive Display in a Car Instrument Cluster Equipped with TFT Display
The high-end instrument clusters in vehicles integrate typically a TFT display between the analog gauge clusters. Further, some car OEMs have started to also request some small customized passive displays integrated inside the analog clusters to display additional technical information.

The microcontrollers tailored for dashboard applications have evolved to include more features, such as higher CPU performance, increased memory size, TFT display control unit, 3D graphic engine, etc., but, as a consequence, do not include anymore the passive LCD driving circuitry. A dedicated standalone LCD driver is then required to drive the additional small 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.

High Immunity to EMI
The increased complexity and electronics in many applications have led to increased electromagnetic interference (EMI) issues and requires components with higher immunity.

When the display is exposed to electrostatic discharge or transients from switching 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 the application module for the following reasons:

  • Instead of driving the display from the MCU, the PCA8561, thanks to its tiny package, can be mounted close to the display, thus avoiding multiple sensitive connections from the MCU to the display and simplifying the PCB design.
  • It offers the possibility to switch off the Power-On-Reset (POR) circuitry through the Power-On-Reset Enable (PORE) pin. EMI could, in fact, trigger the POR circuitry of the display driver, which puts the chip in reset and switches off the display. If the system is subject to EMI, it is recommended to switch off the POR functionality.
  • It specifies ultra low power current consumption; a BOOST function is implemented to increase the driving capability of the display signals in case of bigger display loads.
  • It offers the possibility to check if a severe EMI event has occurred, by simply checking its response by reading the internal registers.
  • It offers the software reset command and the hardware reset pin; if an EMI failure is detected, the MCU can easily reset the display driver and enable again the display, thus avoiding any stuck condition.

Easy Visual Inspection
In a standard HVQFN package, the sides of the terminals consist of bare Cu, which may not be wetted during reflow soldering. Non-wetting failures are difficult 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 cost effective. 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 optical inspection.

Figure 2: Wettable flanks on the HVQFN package

Figure 2: Wettable flanks on the HVQFN package

The PCA8561 solves all the most common challenges in automotive applications, making it the ideal display driver for low resolution segmented LCDs.