Microcontrollers for LCD displays

What is a Microcontroller that is used on LCD Displays?

To understand how microcontrollers for LCD displays work, lets look at the definition of microcontroller according to wikipedia. A microcontroller is a small computer (SoC) on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of Ferroelectric RAM, NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM.

The long and short of it is that the microcontroller on a LCD is the brains behind the LCD. LCD display manufactures refer to the uC (microcontrollers) as a controller driver. The primary purpose of the microcontroller driver is to convert the customer’s firmware into letters, numbers and graphics that are displayed on the LCD. Firmware is software instructions that are written just for the LCD displays.

LCD manufactures for microcontrollers are not common household names

When you purchase a computer the label reads ‘Intel’ or ‘AMD’. Two names that are very well known by most consumers. Microcontrollers that are built just for LCD displays include names such as Sunplus, Sitronix and Tomato (you might think that tomato is a funny name for a company, but hey look what happened with apple). These names are not famous, but their products are used in everything from credit card readers to home security systems.

Why do Microcontrollers for LCD Displays cause such grief?

Controller driver manufactures have a habit of discontinuing the production of the chips every so often. This leaves the customer in need of a replacement. When a controller driver is discontinued (also known as end-of-life) the manufacture will recommend equivalent microprocessors. This is where the grief can begin.

Equivalent does not always mean 100% drop-in replacement. It has been our estimation that an equivalent controller driver is a direct cross 95% of the time. For the other 5%, this is where the grief begins.

When we notify a customer that the Controller/Driver is being phased out they have three options.

1. Order new samples of the LCD with another equivalent microprocessor. The customer will then plug in the display and see if this controller works correctly. If so, then the problem is solved. Although there have been cases where the manufacture of the compatible controller/driver will require a high MOQ (Minimum order quantity).
2. Offer a last time buy of the old controller driver. When we find out the controller is being discontinued there usually is enough time for the customer to place a large order of the outdated controller. The advantage is that the customer will have a product that will work for a limited future production and any units that need to be repaired. The disadvantage is that they may need to purchase several year’s worth of product. This ties up cash and takes up space in the warehouse.
3. The customer could rewrite their firmware. Firmware is software that is written by the customer that communicates with the LCD. This is not always the best option for two reasons.
   1. This will require time and expense for a programmer to rewrite the firmware and test it.
   2. The new microcontrollers for LCD displays will not work on the old product when they come in for repairs.

How Focus LCDs Handles Microcontrollers for LCD displays

We find that the controller driver is one of the most frustrating aspects of the LCD business. That is why it is critical that we call out the model number of each microcontroller that the customer approves. This is called out not on only in our part number but also in the description of that part number. Many of our competitors call out a microprocessors model number and then add the two words “or equivalent”. We will not, we make sure we call out the controller on every order.