I am designing a device for an automotive application.
I have put in 2 separate grounds for my device:
-uC ground, this is for the uC and other ICs, the ground current should be about 150ma. Having a solid ground is very important.
-Heater ground. Part of the device function is to control a heater element to maintain a certain temperature. The heater is pulsed on/off @ 190khz, and the max instantaneous current is about 5A. I do not really care how noisy the heater ground is.
I decided to split the ground, because in the current design I tie both grounds together on the pcb and the heater seems to be causing too much noise on the ground.
My question is where is the best location to hook up the 2 grounds for a car:
- Tie the uC ground closest to the battery and tie the heater ground farther down.
-Tie the heater ground closest to the battery and tie the uC ground farther down
-Tie them both together closest to the battery.
-Other option, please enlighten me.
Keep in mind the primary concern is that the uC ground is nice and clean.
My gut feeling is that tieing the uC ground closest to the battery and the heater ground farther down is the correct solution.