Hi NXP supportors,
I bought 2 EVBs of https://www.nxp.com/design/designs/rd33771-48vevm-reference-design:RD33771-48VEVM#Design-Resources and facing an issue that from its schematics I can't find where is the current path when I connect a battery pack or using a slider battery pack emulator.
search VB_ISENSE_+ or VB_ISENSE_- but got nothing from
RD33771-48VEVM Schematics
Dear KuoShu Lin,
in case of RD33771-48EVM, the shunt resistor must be connected on the thick metal connectors.
Isense+ is a pin 56 and Isense- is a pin 57 on the MC33771B.
Please note, that you must calculate your shunt resistor size, so the voltage between the Isense+ and Isense- will be maximally +/-150mV. Higher voltage, than +/-150mV might permanently damage the board or the MC33771B.
With Best Regards,
Jozef
hi Jozef,
I know shunt resistor must be connected on thick metal connector shown below
but shunt resistor must be connected with a Battey (regardless of battery pack is 48V or 24V or 12V..)
otherwise there'll be no current flow (output by battery) going thru shunt resistor, agree?
that's exactly my question, I don't see any pad of thick metal connector connected with battery pins(CELL0 or CELL14).
in other word, the shunt resistor is a floating situation (where is the current flow coming from ?)
please take a look of below circuitry again, there should has a current flow(provided by a battery) going thru SHUNT R470, but from scematics I don't any trace or path of battery (J3) connected with VB_ISENSE_+ or VB_ISENSE_-
Hi KuoShu Lin,
this is a misunderstanding. I thought you are asking where the shunt resistor pins should be connected on the RD33771-48VEVM. Please see my answers below.
But shunt resistor must be connected with a Battey (regardless of battery pack is 48V or 24V or 12V..)
otherwise there'll be no current flow (output by battery) going thru shunt resistor, agree?
[A] Yes, I agree. I am not sure if there is a shunt R470 populated on the RD33771-48VEVM. I have asked an application team if the shunt is populated, if it must be added externally.
that's exactly my question, I don't see any pad of thick metal connector connected with battery pins(CELL0 or CELL14).
in other word, the shunt resistor is a floating situation (where is the current flow coming from ?)
please take a look of below circuitry again, there should has a current flow(provided by a battery) going thru SHUNT R470, but from schematics I don't any trace or path of battery (J3) connected with VB_ISENSE_+ or VB_ISENSE_-
[A] Depends if there is shunt resistor populated on the RD33771-48VEVM the picture might be or might be not correct. If there is no shunt included on the RD33771-48VEVM, I think its incorrect. If there is a shunt included, it might be correct.
Please see my proposed correction below if the shunt must be added externally.
I have asked the application team for confirmation if the proposed correction is correct. Before you start connecting anything please wait for a reply from the application team.
With Best Regards,
Jozef
hi Jozef,
I marked correct shunt position(below rectangle metal circled in red) and VB_ISENSE_+ and VB_ISENSE_- positions below,
issue is at here: when 48V battery connects to J3 --> there's no any current path connects 48V with shunt. hopefully you can understand what I mean.
