MP6619s SGND mystery

We have MP6619 Eval board. However The voltage at Iset to GND measures about 0.8V no matter where the pot is set…shouldn’t it measure around 0.15V?? When we move the pot RV1, the Iset reading is not changing (stays around 0.8V)…any idea why? We are trying to set our current limit.

Noticed there is a different sgnd at pin 4 of CN1 (we connected to the large pin gnd instead). Are these GND, SGND and AGND tied together? Where? SGND shows being tied to agnd which goes nowhere on the eval schematic, yet the eval board just labls them as GND at all the wiring pins.
GND of R11, c8, C1, etc does not seem to tie to SGND anywhere. Why does the eval manual not mention sgnd?

Hello nnovotney,

Have any modifications been made to the EV6619?
What conditions are you running the EVB at?

SGND, GND, and AGND are tied together. This is more clear on the layout.

If you float the Iset resistor, what voltage are you seeing on the Iset pin?

Vinh Tran

Not sure what you mean by float the ISET resistor, since it is a pot tied to gnd…how would you float it?
The board was hooked up to 12V and a motor, as you can see Iset is reading 0.8V …is that normal? why?