Hello,
We need to drive a small 3V DC motor from a battery, with 100mA current limitation and stall detection.
(The motor we use has around 30uH / 20Ohm Impedance, and 20mA no load current)
After a long search, the BQ25173 looks perfect for our application, as we can set the desired output voltage and current limit.
And for stall detection, the STAT output has exactly the same logic as a STALL signal.
We are testing it with the EVM and everything is working fine except one strange behaviour :
Sometimes, especially when the average current is low, the output voltage is suddenly dropping to 0, like if the regulator is switching off the output.
It stays low during 41ms, then goes up again. This can happen only once, or repeat during many seconds.
You can see this drop to zero happening twice on the scope below :
A few observations we made :
This strange behavior is happening continuously when the motor has been cooled, and becomes less frequent when it warms up.
Adding 10uF capacitor to the output is helping, it seems the issue is not happening anymore.
Adding resistive load in parallel to the motor is also helping. With 300R (= +10mA) the issue is much less frequent.
This DC motor is generating a lot of noise on the ISET pin (and the setup with floating wires is not helping)
It seems the BQ25173 is reacting to this noise, especially when the signal is close to 0.
Do you have an idea what is happening when the output is suddenly going low for 41ms ?
Should we just increase the output cap, or is there a better way of avoiding this behaviour ?
We also see you released BQ25173-Q1, is it maybe more robust against noise ?
Thank you in advance for your help !
