Hello,I am working on L6235PD.Is it necessary to use TACHO pin output to develop speed control loop or i can other 5V supply that i used for pull up purpose to generate speed control loop.

[Cristiana SCARAMEL]

Hello @Pvalv.1​ and welcome to the ST Community.

I did not understand what your question is.

The TACHO pin is a frequency-to-voltage open drain output. Every pulse from pin H1 (Hall effect sensor input 1) is shaped as a fixed and adjustable length pulse.

Providing an external pull-up resistor on this open drain output, the resulting waveform at the TACHO pin will be a square-wave whose frequency is proportional to the motor rotation speed.

You can find more details about the tachometer function and how to work the TACHO pin in the L6235 datasheet (starting from page 20), in Figure 17 a Tachometer speed control loop example is shown.