What is the refresh rate of a 1.33 inch Sharp Memory TFT in frames per second?
The refresh rate of a 1.33 inch Sharp Memory TFT display is not a fixed number like you’d see on a gaming monitor or a smartphone screen. Instead, it depends entirely on how you drive it. In its standard operation mode, the panel can update at a maximum of about 60 frames per second (fps) when you’re writing new content to the entire display. But here’s the kicker: because of its unique memory-in-pixel architecture, the display doesn’t need to refresh continuously to hold an image. Once you write data to it, the pixels latch onto that state and maintain it without any power draw. So the effective “refresh rate” for static content is effectively zero Hz—it’s a static image that stays put indefinitely. For dynamic content, the practical limit is around 60 fps, but you can push it lower if you’re updating partial regions, which saves power and reduces bus traffic. This is a Memory-in-Pixel (MIP) technology, not a traditional TFT-LCD, so the refresh behavior is fundamentally different. To get the full specs and driving details, you can check the 1.33 inch sharp memory tft display product page.
Let’s break down the numbers. The display’s resolution is 128x128 pixels, which is 16,384 pixels total. The interface is SPI (Serial Peripheral Interface), typically running at clock speeds up to 10 MHz or more, depending on the controller. To update the full frame, you need to send 16,384 bits of pixel data plus command overhead. At 10 MHz SPI, a full frame write takes roughly 1.6 milliseconds (16,384 bits / 10,000,000 bits per second = 0.0016384 seconds). That’s about 610 frames per second theoretically, but the display’s internal timing and pixel response time limit it to around 60 fps in practice. The pixel response time is specified at about 10 milliseconds for a full transition, which is where the 60 fps cap comes from—it’s the same as a typical LCD’s response time. However, because the pixels are bistable (they hold their state without power), you don’t need to refresh the display at all for static content. This is a huge advantage for e-paper-like applications, like smart badges, shelf labels, or IoT devices, where you update the screen infrequently and want to save battery.
One critical detail: the refresh rate is not a spec you’ll find in the datasheet as a single number. Sharp’s Memory LCDs are designed for low-power, static-image applications, so the datasheet focuses on power consumption, pixel retention, and interface timing. For example, the typical power consumption is around 0.1 mW when updating at 60 fps, and it drops to near zero when the image is static. Compare that to a standard TFT-LCD, which consumes power continuously to refresh pixels even when the image doesn’t change. The 1.33 inch panel uses a 1-bit per pixel color depth (monochrome), so each pixel is either black or white. That’s why the data rate is low—you’re only sending 1 bit per pixel, not 24 bits like in a color TFT. This makes it extremely efficient for text and simple graphics.
Let’s talk about partial updates. If you only need to change a small area of the display, you can send data only for that region. The SPI interface supports addressing specific rows and columns, so you can update a 10x10 pixel area in about 0.1 milliseconds. This is where the effective refresh rate becomes flexible. For example, if you’re animating a small icon, you could update that region at 1000 fps theoretically, but the pixel response time still limits you to around 60 fps for visible changes. The display’s controller handles the timing internally, so you don’t need to worry about tearing or ghosting as long as you respect the pixel transition time. The datasheet specifies a typical pixel response time of 10 ms, but it can vary between 5 ms and 15 ms depending on temperature and voltage. At 25°C, it’s around 10 ms. At -20°C, it might slow to 20 ms, which would drop the effective refresh rate to 50 fps. At 60°C, it might speed up to 5 ms, allowing up to 200 fps, but the controller and SPI bus become the bottleneck then.
Here’s a table to summarize the key timing parameters from the datasheet:
| Parameter | Value | Notes |
|---|---|---|
| Resolution | 128 x 128 pixels | 16,384 pixels total |
| Pixel color depth | 1 bit (monochrome) | Black or white |
| Pixel response time | 10 ms (typical) | At 25°C, ranges 5-15 ms |
| SPI clock speed | Up to 10 MHz | Depends on MCU and wiring |
| Full frame write time | ~1.6 ms | At 10 MHz SPI |
| Max full frame refresh rate | ~60 fps | Limited by pixel response |
| Partial update time | ~0.1 ms per 10x10 area | Depends on region size |
| Static power consumption | ~0.1 mW (active update) | Near zero when static |
In real-world applications, the refresh rate you choose depends on your use case. For a digital clock, you might update the seconds digit every second, so the effective refresh rate is 1 fps. For a scrolling text display, you might update at 10 fps to keep the text readable without flicker. For a fast-moving animation, you’d push it to 60 fps, but you’ll need a microcontroller that can handle the SPI writes efficiently. The display’s controller includes a built-in oscillator that manages the pixel latching, so you don’t need external timing. The SPI interface is 3-wire (CS, SCLK, SDI) plus a separate VCOM signal for the common voltage. The VCOM signal toggles at a specific frequency (typically 60 Hz) to prevent pixel degradation over time, but this is not the same as a refresh rate—it’s a biasing signal that the display uses internally. The datasheet says VCOM should be toggled at least once every 10 seconds to maintain pixel integrity, but in practice, you can leave it static if you’re updating the display frequently.
Another angle: the display’s memory is SRAM-based, not flash-based. Each pixel has a 1-bit SRAM cell that holds the state. When you write data, the SRAM is updated, and the pixel driver applies the voltage to set the liquid crystal. The SRAM retains the data as long as power is supplied, but the pixel itself is bistable—it holds the optical state even if power is removed. This is a key difference from e-ink displays, which use electrophoretic particles and have slower response times (hundreds of milliseconds). The Sharp Memory LCD is much faster, with response times in the millisecond range, making it suitable for video-like applications at low frame rates. But don’t expect it to handle 60 fps video smoothly—it’s designed for simple graphics and text, not full-motion video. The contrast ratio is typically 10:1, and the viewing angle is 170 degrees, which is excellent for a monochrome display.
Let’s get into the gritty details of driving the display. The SPI protocol uses a 9-bit command/data format: the first bit indicates whether the following 8 bits are command or data. For a full frame write, you send a command to set the row address, then send 128 bytes of pixel data (one byte per column, with each bit representing a pixel in that column). The display supports 128 rows, so you repeat this for each row. That’s 128 x 128 bits = 16,384 bits total, or 2,048 bytes. At 10 MHz SPI, that’s 2,048 bytes x 8 bits/byte = 16,384 bits, divided by 10 MHz = 1.6384 ms. But the display’s internal timing adds a small overhead for each row write, typically a few microseconds. So a full frame update takes about 2 ms total. That’s 500 frames per second in theory, but the pixel response time of 10 ms limits you to 100 fps. However, the datasheet recommends a minimum frame period of 16.6 ms (60 fps) to avoid image artifacts. Why? Because the liquid crystal molecules need time to settle, and writing faster than 60 fps can cause incomplete transitions, leading to ghosting or reduced contrast. So the 60 fps limit is a practical recommendation, not a hard electrical limit.
Temperature effects are significant. At low temperatures, the liquid crystal viscosity increases, slowing the pixel response. At 0°C, the response time might double to 20 ms, dropping the max refresh rate to 50 fps. At -20°C, it could be 30 ms or more, limiting you to 33 fps. At high temperatures, the response speeds up, but the contrast ratio might degrade above 60°C. The operating temperature range is -20°C to +70°C, so you need to account for this in your design. For outdoor applications in winter, you might need to reduce the refresh rate or use a heater. The display’s power consumption also varies with temperature—at low temperatures, the internal oscillator might draw more current to maintain timing accuracy.
One more thing: the display’s interface is designed for low pin count, which is great for small microcontrollers. But the SPI bus speed can be a bottleneck if you’re using a slow MCU. For example, an Arduino Uno running at 16 MHz can only generate SPI clock speeds up to 8 MHz, which gives a full frame write time of 2.05 ms. That’s still 487 fps theoretical, but the pixel response limits it. However, the Arduino’s software overhead for sending SPI data can add microseconds per byte, so the actual write time might be 5-10 ms per frame, dropping the effective refresh rate to 100-200 fps. But again, the pixel response is the real limiter. If you’re using a faster MCU like an ESP32 or STM32, you can push the SPI clock to 20 MHz or more, but the display’s internal logic might not handle it—the datasheet specifies a maximum SPI clock of 10 MHz. So stick to that.
In summary, the refresh rate of this display is a moving target. For static images, it’s infinite—the image stays without any refresh. For dynamic content, you can achieve up to 60 fps full frame updates, but partial updates can be much faster in terms of data rate, though the pixel response still caps the visible change rate at around 60 fps. The display’s unique memory-in-pixel design makes it ideal for battery-powered devices where you need to update the screen occasionally and save power. The 1.33 inch size is perfect for compact wearables, smart home controls, or industrial indicators. The 128x128 resolution gives you enough space for text and simple icons, and the 1-bit color depth keeps the data rate low. If you’re designing a product that needs a low-power, high-contrast display with moderate update speeds, this is a solid choice. Just remember to account for the pixel response time and temperature effects in your software, and you’ll get reliable performance at 60 fps or less.