Originally a DRV8305N was used on a board design but it got switched to a DRV83053 variant.
The Vreg pin (outputs 3.3V from the DRV internal LDO) is connected to our boards switching regulator (LMR36015-Q1).
The question here is will this connection of the outputs of the 2 regulators affect the motor control performance of the DRV8305 in any way
One of our chief concerns is how/if this will change with temperature variance
Hi Adam,
Thanks for your response.
I looked at section 8.2.3 of the datasheet and I am not seeing any considerations for the VREG pin that you mentioned. 8.2.3 is just application curves for the DRV.
what current limiting resistor are you talking about as well? I dont see any mention of that either.
The schematic elements that you asked for are attached.
As you can see the 3.3Vs are tied together and power goes to the elements on this board and on others.
I did find this TI paper that says tying an LDO to a DC/DC converter will help with stability. Any comments regarding that in this case?
Hi Kevin,
We are having severe inclement weather in Dallas and multiple team members are without power. Please be patient with our response here.
In my opinion - and I'll wait for Adam to return as the expert here - You may end up damaging the DRV8305 since the LDO output was not intended to "fight" against a buck regulator.
From the document that you referenced, one key parameter for the design of an LDO & DC/DC on the same output is "... that the [buck] converter output is set at a higher voltage than the maximum LDO output voltage." This is because if the DC/DC output is lower than the LDO the LDO will try to fight the stronger buck regulator to push the output up - and the buck will win. If you can guarantee that the min buck output voltage is always higher than the max LDO output voltage, the LDO power path will remain OFF and operate as intended.
Thanks,
Matt
