Detailed Comparison of High Speed Voltage Level Shifting

This is a detailed comparison of Voltage Level Shifting from 3.3V logic to 5V logic, specificly for driving Addressable pixels.

In this test I used an ESP8266 set up to transmit data at different frequencies over the SPI port.

The top 5 screenshots use a single SK9822 pixel.

The bottom screenshots use the SN74HCT245N.

5 Diferent SPI frequenies were tested: 1Mhz, 5Mhz, 10Mhz, 15Mhz & 20Mhz.

The SK9822 pixel is consistently over 4.5V BUT at 15Mhz and UP drops to 4.4 and 3.7 which becomes useless. However the The SN74HCT245N is consistently between 5.3-5.3V even at 20Mhz. I did not test at a faster rate because the SK9822 pixel has a maximum “imaginative” rate of 30Mhz, although driving strands longer than 100 pixels becomes impossible without serious RF insulation. The APA102 pixel, on which the SK9822 is based, has an maximum rate of 20Mhz Which is almost impossible to reach.