Hi
I order three boards from a distributor of yours, and as i am waiting for the delivery i have some time to check for the details.
So i have some questions about cooling the chip and setting the current limit.
According to Allegro manual found on your site:
“Layout The printed circuit board should use a heavy groundplane.
For optimum electrical and thermal performance, the
A4983 must be soldered directly onto the board. On the underside
of the A4983 package is an exposed pad, which provides a
path for enhanced thermal dissipation. The thermal pad should be
soldered directly to an exposed surface on the PCB. Thermal vias
are used to transfer heat to other layers of the PCB. Thermal vias
should not have any thermal relief and should be connected to
internal layers, if available, to maximize the dissipation area.”
Is this implemented in your board? and if so, is the plane electrically isolated or is connected to the ground? have you any suggestions of how to secure a heat sink on the board ?
The second thing is about current limiting. Again according to the manual :
“The transconductance
function is approximated by the maximum value of current
limiting, ITripMAX (A), which is set by
ITripMAX = VREF / ( 8 * RS)
where RS is the resistance of the sense resistor (Ω) and VREF is
the input voltage on the REF pin (V).”
And later:
“It is critical that the maximum rating (0.5 V) on the SENSE1 and
SENSE2 pins is not exceeded.”
With the value of Rs = 0.05 Ohms the above equation gives us a maximum of 1.25A which is much lower than the 2A written in the description of your board. Am i missing something.
Thank you in advance.