0
\$\begingroup\$

The datasheet for the ISL83204A full-bridge driver chip documents "low sense" pins that connect to the source of the bottom N-channel MOSFETs. As those are typically connected to ground, what is the function of these pins?

The data sheet does not mention these pins, except briefly as follows: Absolute max: +/- 2V compared to GND. Normal operation: +/- 1V compared to GND.

There's a diagram that shows "optional" resistors below the ALS and BLS pins, which look like current sense resistors, but there's no mention of whether this chip has current sense, over-current shut-off, or anything like that.

\$\endgroup\$
0
\$\begingroup\$

"ALS" does not stand for "A low sense", it stands for "A low source". The two lines ALS and BLS provide the means to reference the MOSFET gate drives to the sources of the respective MOSFETs. They are not typically connected to ground. It is expected that there will be current sense resistors to ground. The outputs of these resistors, properly conditioned, are fed back to the input comparator to control the cycling of the bridge.

\$\endgroup\$
  • \$\begingroup\$ Thanks for the answer. I see the separate external comparator used for "hysteresis mode switching" (which I'm not doing.) I also see ALS and BLS go into the VSS (low-side entry) for the "driver" stage in the internal block diagram. What I don't understand is why the driver wouldn't just be referenced to ground anyway. There is no bootstrap driving the lower gates, so what's the purpose of allowing up to 1V delta in ALS/BLS as opposed to GND? \$\endgroup\$ – Jon Watte Apr 21 '14 at 4:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.