L6206Q - SENSE resistors required or not?

[wnm4]

The L6206Q datasheet Figure 14 "Typical Application" does not show the use of any additional SENSE_A or SENSE_B resistors connected to pins 45/46 & 15/16 respectively.  Section 4.3 talks about "the external current sense resistor normally used [being] eliminated."   AN1762 in section 3.5, discusses the selection of sense resistors and suggests that they might be part of the over-current setting process (which the datasheet suggests is handled entirely by the R_CL resistors).

So which is correct? Datasheet or AN?  Are sense resistors required or not?  If they are required, how are they selected and how does that selection work with the selection of R_CL current limit resistors?

[Peter BENSCH · Accepted solution]

Welcome @wnm4, to the community!

You have allowed yourself to be confused by two fundamental differences:

• The resistors connected to PROGCLA/B are used to set the overcurrent protection, which is implemented via the OCD comparator shown in fig. 9 of the data sheet. For this use case, sense resistors are not actually necessary due to internal current detection.
• The resistors connected to SENSEA/B are placed in the low‑side return path and can be used to generate a Vsense​ that is processed by an external PWM current controller. This is not (and should not be confused with) the internal OCD mechanism of the L6206Q, but an application‑level current regulation/metering mechanism.

So whether sense resistors should be used depends on your application and requirements. If you want to use them, you will find calculation notes in the AN1762 mentioned above, section 3.5, for example.

Does it answer your questions?

Regards
/Peter

[wnm4]

Thank you Peter, this does indeed answer my question.