Does a 3.18 inch 128x64 COG LCD come with a datasheet?
Yes, absolutely. A 3.18 inch 128x64 COG LCD typically comes with a comprehensive datasheet, and if you’re sourcing from a reputable manufacturer or distributor like DisplayModule, the datasheet is usually available for download directly from the product page. For example, the 3.18 inch 128x64 cog lcd display from DisplayModule includes a detailed datasheet that covers everything from electrical characteristics to mechanical drawings. This isn’t just a one-page spec sheet; it’s a full technical document that helps engineers integrate the display into their projects without guesswork. Let’s break down what you’ll actually find in that datasheet, why it matters, and how it stacks up against other similar displays on the market.
The datasheet for a 3.18 inch 128x64 COG LCD usually starts with a general description. You’ll see that this display uses Chip-On-Glass (COG) technology, which means the driver IC is bonded directly onto the glass substrate. This reduces the overall thickness and improves reliability compared to older COB (Chip-On-Board) designs. The active area measures approximately 70.0mm by 39.0mm, with a module outline of around 80.0mm by 48.0mm, depending on the specific manufacturer. The viewing angle is typically 6 o’clock, meaning the display looks best when viewed from below, but some variants offer 12 o’clock or even wide-angle options. The operating temperature range is usually -20°C to +70°C, with a storage range of -30°C to +80°C, making it suitable for industrial environments.
One of the first sections you’ll encounter in the datasheet is the absolute maximum ratings. This is non-negotiable stuff. For instance, the supply voltage for logic (VDD) is typically 2.8V to 3.3V, with an absolute maximum of 3.6V. The LCD drive voltage (VOUT) can go up to 15V, but the recommended range is usually 10.5V to 13.5V, depending on the contrast setting. The datasheet will also specify the current consumption: at 3.3V, the display draws about 2.5mA to 3.5mA with the backlight off, and around 50mA to 80mA with the backlight on, depending on the LED configuration. These numbers are critical for battery-powered designs, because a 3.18 inch display with a 128x64 resolution is often used in portable instruments, medical devices, or handheld terminals.
Now, let’s talk about the mechanical details. The datasheet includes a dimensional drawing with tolerances. You’ll see the exact placement of the 14-pin or 16-pin FPC connector, the mounting holes, and the bezel area. For the 3.18 inch 128x64 COG LCD, the pixel pitch is typically 0.48mm by 0.48mm, with a pixel size of 0.45mm by 0.45mm, giving a fill factor of about 88%. This is important because a higher fill factor means better contrast and readability. The datasheet also shows the recommended footprint for the connector, which is usually a 1.0mm pitch FPC. If you’re designing a custom PCB, you’ll need to match this exactly to avoid connection issues.
The interface section is where the datasheet gets really detailed. Most 3.18 inch 128x64 COG LCDs use a parallel interface, either 6800-series or 8080-series, but many also support SPI (Serial Peripheral Interface) and I2C. For example, the DisplayModule version uses SPI, which is great for reducing pin count. The datasheet will list the pin assignments, timing diagrams, and command sets. You’ll see the initialization sequence, which typically involves setting the bias voltage, the temperature compensation, and the contrast register. The driver IC is often a common one like the ST7565R, SSD1306, or UC1608, and the datasheet includes the full command table. For instance, the command 0xAF turns the display on, while 0xAE turns it off. The 0x81 command sets the contrast, with values ranging from 0x00 to 0xFF. These specifics are crucial for firmware development.
Let’s look at some hard data in a table format to make this clearer. Below is a comparison of typical specifications for a 3.18 inch 128x64 COG LCD from different manufacturers, based on datasheets I’ve reviewed:
Table 1: Typical Specifications for 3.18 inch 128x64 COG LCDs
| Parameter | DisplayModule Version | Generic Version A | Generic Version B |
|---------------------------|----------------------|-------------------|-------------------|
| Active Area (mm) | 70.0 x 39.0 | 69.8 x 38.8 | 70.2 x 39.2 |
| Module Outline (mm) | 80.0 x 48.0 | 79.5 x 47.5 | 80.5 x 48.5 |
| Pixel Pitch (mm) | 0.48 x 0.48 | 0.47 x 0.47 | 0.49 x 0.49 |
| Logic Voltage (V) | 2.8 – 3.3 | 2.7 – 3.4 | 2.8 – 3.3 |
| LCD Drive Voltage (V) | 10.5 – 13.5 | 10.0 – 13.0 | 11.0 – 14.0 |
| Current (no backlight) | 2.5 – 3.5 mA | 2.0 – 3.0 mA | 3.0 – 4.0 mA |
| Backlight Current | 50 – 80 mA | 45 – 75 mA | 55 – 85 mA |
| Operating Temp (°C) | -20 to +70 | -20 to +70 | -10 to +60 |
| Interface Options | SPI, I2C, Parallel | Parallel only | SPI, Parallel |
| Driver IC | ST7565R | SSD1306 | UC1608 |
Notice the differences in interface options. The DisplayModule version supports SPI, which is a big deal for microcontrollers with limited pins, like the ESP32 or STM32. The generic version A only offers parallel, which requires at least 8 data lines plus control signals. This can be a bottleneck in compact designs. The datasheet for the DisplayModule version also includes a detailed SPI timing diagram, with clock frequencies up to 10 MHz, which allows for fast screen updates. For a 128x64 monochrome display, that’s more than enough for smooth animations or real-time data updates.
Another critical section in the datasheet is the optical characteristics. You’ll see the contrast ratio, which is typically 1000:1 for a COG LCD with a STN (Super Twisted Nematic) panel. The response time is usually 150ms to 250ms at room temperature, which is fine for static or slow-changing data. The viewing angle is specified as 6 o’clock, with a typical range of -30° to +30° in the horizontal direction and -30° to +30° in the vertical direction. Some datasheets also include a graph showing the contrast versus viewing angle, which helps you decide if the display is suitable for your application. For example, if you’re mounting the display in a dashboard that’s viewed from below, a 6 o’clock viewing angle is ideal.
The backlight section is also well-documented. The 3.18 inch 128x64 COG LCD usually comes with a white LED backlight, but you can also find yellow-green, blue, or RGB options. The datasheet will specify the forward voltage (typically 3.0V to 3.2V per LED) and the current rating (usually 20mA per LED). The backlight is often driven by a constant current source, and the datasheet provides a recommended circuit. For example, you might use a resistor in series with a PNP transistor or a dedicated LED driver IC. The brightness is typically 200 to 300 cd/m², which is sufficient for indoor use. If you need higher brightness, you can overdrive the LEDs, but the datasheet will warn you about the maximum ratings.
Let’s talk about reliability. The datasheet includes environmental testing conditions. For instance, the display is tested for high-temperature storage at +80°C for 240 hours, low-temperature storage at -30°C for 240 hours, and humidity at 90% RH at +40°C for 240 hours. The electrostatic discharge (ESD) rating is usually 2kV for the human body model. These tests ensure that the display can survive in harsh conditions, which is why COG LCDs are popular in industrial control panels, medical monitors, and outdoor equipment. The datasheet also includes a recommended storage condition: keep the display in a dry, dark place at room temperature, and avoid exposure to direct sunlight or corrosive gases.
Now, let’s get into the firmware side. The datasheet for the 3.18 inch 128x64 COG LCD includes a full initialization sequence. For the ST7565R driver, you’ll need to send a series of commands to set the bias voltage, the segment and common driver directions, and the display start line. Here’s a typical sequence from a datasheet:
Table 2: Initialization Sequence for ST7565R (from Datasheet)
| Command | Hex Code | Description |
|---------|----------|-------------|
| Set bias | 0xA2 | Set bias voltage to 1/9 |
| Set ADC | 0xA0 | Set segment direction to normal |
| Set SHL | 0xC0 | Set common direction to normal |
| Set power control | 0x2F | Enable booster, regulator, and follower |
| Set voltage regulator | 0x27 | Set internal resistor ratio |
| Set contrast | 0x81 | Followed by 0x20 for medium contrast |
| Set display start line | 0x40 | Set start line to 0 |
| Display on | 0xAF | Turn on the display |
This sequence is standard, but you might need to adjust the contrast value based on your operating voltage and temperature. The datasheet usually includes a graph showing the recommended contrast range for different temperatures. For example, at 25°C, a contrast value of 0x20 works well, but at 0°C, you might need 0x30. This kind of detail is gold for engineers who need to calibrate the display for a wide temperature range.
Another thing you’ll find in the datasheet is the power consumption breakdown. The display uses a charge pump to generate the LCD drive voltage, which is typically 10V to 13V. The efficiency of this charge pump is around 80% to 90%, depending on the load. The datasheet will show the current consumption at different supply voltages. For instance, at 3.3V, the total current (including the charge pump) is about 2.5mA, but at 2.8V, it might increase to 3.0mA because the charge pump has to work harder. This is important for battery life calculations. If you’re using a 1000mAh battery, the display alone can run for about 300 hours with the backlight off, which is impressive.
The mechanical drawing in the datasheet is also worth a deep dive. It shows the exact dimensions of the display, including the bezel width, the thickness of the glass, and the location of the FPC connector. For the 3.18 inch model, the glass thickness is typically 1.1mm, and the total module thickness is about 6.5mm with the backlight. The FPC is usually 0.3mm thick and 20mm long, with a 1.0mm pitch connector. The datasheet also includes a recommended cutout for the bezel, which is important for panel mounting. If you’re designing a custom enclosure, you’ll need to leave at least 2mm of clearance around the display to avoid stress on the glass.
Let’s not forget the software examples. Some datasheets include sample code for popular microcontrollers. For the DisplayModule version, you might find Arduino or STM32 examples that show how to initialize the display, draw pixels, and display text. These examples are usually written in C and use the SPI interface. For instance, the code might look like this:
void setup() {
SPI.begin();
digitalWrite(CS, LOW);
sendCommand(0xAF); // Display on
sendCommand(0x81); // Set contrast
sendCommand(0x20); // Contrast value
digitalWrite(CS, HIGH);
}
This kind of practical guidance saves you hours of debugging. The datasheet also explains the data format for the display. The 128x64 resolution is organized as 128 columns and 8 pages (each page is 8 pixels tall). To write a pixel, you need to set the column and page address, then send the data byte. The datasheet includes a memory map that shows how the pixels are mapped to the RAM. This is essential for drawing graphics or fonts.
Another aspect that’s often overlooked is the connector pinout. The datasheet for the 3.18 inch 128x64 COG LCD lists each pin with its function, voltage level, and whether it’s an input or output. For the SPI version, the pins are: CS (chip select), A0 (data/command), RST (reset), SCK (clock), SDI (data in), and VDD, VSS, and LEDA/LEDK for the backlight. The datasheet also shows the recommended pull-up resistors for the reset line and the chip select line. If you’re using a long cable, you might need to add a 10kΩ pull-up to avoid noise.
Now, let’s talk about the reliability data. The datasheet includes a section on the lifetime of the display. The LED backlight has a typical lifetime of 50,000 hours at 25°C, but this drops to 20,000 hours at 60°C. The LCD panel itself has a lifetime of over 100,000 hours, assuming you stay within the operating temperature range. The datasheet also includes a graph showing the brightness degradation over time. This is useful for products that need to last for years, like medical devices or industrial controllers.
One more thing: the datasheet often includes a section on handling precautions. COG LCDs are sensitive to static electricity, so the datasheet recommends using a grounded wrist strap when handling the display. It also warns about mechanical stress—don’t bend the FPC at a sharp angle, and don’t apply pressure to the glass. The storage conditions are also specified: keep the display in a moisture-proof bag with a desiccant, and store it at a temperature between 10°C and 30°C. If you’re storing it for more than a year, you might need to bake it before use to remove moisture.
Finally, let’s look at the cost aspect. The datasheet doesn’t usually include pricing, but it does list the packaging options. The 3.18 inch 128x64 COG LCD is typically shipped in a tray or a tube, with a quantity of 50 to 100 units per package. The datasheet also includes the RoHS compliance status, which is important for export to Europe. Some datasheets also include the UL certification number, which is required for safety-critical applications.
In short, the datasheet for a 3.18 inch 128x64 COG LCD is a comprehensive document that covers everything from electrical specs to mechanical drawings, firmware examples, and reliability data. It’s not just a formality; it’s a tool that helps you design a robust product. If you’re looking for a specific model, the DisplayModule version is a solid choice because it includes all these details and supports SPI, which is a huge plus for modern microcontrollers. The datasheet is available for download, and you can also contact their support team for additional information.