CCL BLDC Fan Hardware Suggestions

The accompanying code includes support for adjusting the PWM duty cycle with the on-board button of the ATtiny817 Xplained Mini. Other than this, there is no specific hardware provided or described for this application note. For this reason, and the fact that BLDC motors and their control circuits come in many different varieties, two specific fan hardware layouts that will fit the described device setup are outlined below.

Two-Phase BLDC Fan with Dual Control Input

As the setup described in this application note is designed to take one Hall sensor input and output two PWM control signals, a simple approach would be to use a two-phase BLDC fan motor with a single Hall sensor output and one driver element connected to each phase as illustrated in the figure below. The drivers and Hall sensor need to be connected to the device as indicated.

Figure 1. Outline of a Two-Phase BLDC Fan Motor with Drivers

For this configuration, no shoot-through will occur if both drivers are activated, thus the dead time can in fact be reduced to zero or removed.

One-Phase BLDC Fan with Full H-Bridge Control

In addition to the more basic configuration illustrated above, the described application is also suited for controlling a single-phase BLDC fan motor with a full H-bridge driver circuit by connecting the device as outlined in the figure below. For this configuration shoot-through will occur if both PWM signals are active, thus dead time is needed when switching between what output the PWM pulses are sent to.

Figure 2. Outline of a One-Phase BLDC Fan Motor and a Full H-Bridge