Hi there, I’m using MP2690 to design a portable fan. I noticed when MP2690 SYS output is connected to inductive load (like a fan or motor), Boost mode is not shutdown when PB is held low for 2.5s. But if I switch the load to a resistive one, PB is working just fine & Boost can be shutdown normally,
At first, I suspect it is due to the noise presented on PB line (1.2Vpp). But after I reduce the noise on PB down to 0.4Vpp, the condition still not improving.
I hope MPS can shed some light on this issue. The inductive load tested range from 0.28A to 0.4A.
Hello,
You would need to look at the SYS output, if there is noise from the fan there.
More information is good here, does the circuit work OK with the USB input connected for power?
What kind of fan motor is used, is it brushed or brushless?
If there is excessive noise on the SYS output then adding more capacitance would help. Also adding some capacitance on the input or the battery.
Also with long PB presses, are the LEDs lit? Would indicate PB signal isn’t correct.
Hi James,
Thanks for the response.
Other than PB long press to shutdown issue, the rest of the features are working fine, including charging, boost, USB pass thru mode, etc.
The fan motor used is brushless.
We have used LED for the battery indicator. Those are not shutdown as well after long PB press.
We have attached the SYS ripple graph for your reference.
Following your advice, we have tried adding more capacitors on SYS, VIN, & VBAT. We found the only effective solution is adding an 100uF E-Cap on SYS. This is on top of the 3 pcs 22uF ceramic capacitors we have already put in place.
Attached is the ripple graph after we added the 100uF.
To us, the original ripple is not that high & its reduction after adding the 100uF is also not that much. We are happy that we found a solution for this, the rest would be to study how to mount a100uF on board. But we are also concern if there are things we overlooked as there’s total 166uF on SYS now.
