TX1 in Parallel with Motor


I have my TX1 in parallel with a fairly low power motor, both powered from a 12V lead acid battery.

I am having issues overcoming the sensitivity of the VDD_PWR_BAD line. When the motor is activated the PWR_BAD circuit seems to shut the jetson down.

No filtering, Jetson and motor joined at switch, crashes:

22uF filter cap on TX1 DC jack, Jetson and motor joined at switch, crashes:

Jetson and motor hooked directly to battery, unfused and unswitched, operates as intended:

This is using a homemade plug with no ferrite core. Does anybody know of a common solution to overcoming noisy power with the TX1? Can you refer me to a manual with more detailed specs on the power supply?

Hi, seems the VDD_IN drops > 20% when motor activated and so trigger VIN_PWR_BAD# to low as you can see in Figure 7 of OEM DG. Adding big capacitors might work, or you can consider adding a serial resistor on the branch circuit of motor to decrease the voltage drop when motor power up and so decrease the power up current of motor.

Hi Trumany,

The yellow line was measured at the DC jack. It was level at 13 volts. The voltage drop before reset looks to be about 1.7 volts or 13% over a 1.56 ms period after adding a 22uF cap across the jack.

Is there any reason I shouldn’t desolder C176 so Q31’s gate is pulled down to keep VIN_PWR_BAD_L from being asserted? After bypassing the solar charge controller and giving the motor driver a separate direct wire to the battery the problem is mostly gone (see the third image to visualize the voltage drop - a fuse was added but it looks the same), but I have experienced a couple of faults already with a fully charged and fresh battery. Once things age or the state of charge drops I expect to see many more problems stemming from this.

I removed C176. Problem solved.

C176 is for timing of holding VIN_PWR_BAD# to low until VDD_IN is stable before power on, removing it is not suggested, you can check the OEM DG for details.

I’m under the impression the PMIC and power button prevent power on prior to their activation. They should handle this function just fine, at least in my situation. I am using a 12V lead-acid battery as my power supply, and the only noise on VDD_IN should be from switches. My system uses a microcontroller to simulate the power button press 300 ms after the power switch is enabled, and there isn’t a switch I’ll use that is going to bounce for 300 ms.

EDIT: For future reference, the board seems to have brown-out protection that is about as sensitive as the C176 circuit. Removing C176 made my issue less frequent, but intermittent shutdowns still occurred. A better solution was using isolated batteries for the motor and TX1.