Hi All,

Have you ever encountered similar problem? The PSoC chip resets itself during a test?

I encounter this problem recently. I put PSoC chip and some relays in a same PCB. One of the relays connected to a high voltage (400VDC) and multimeter. PSoC will control the relay to turn on, then multimeter will measure the voltage. But after PSoC send command to turn on the relay, the chip automatically reset itself.

My PSoC is using USB control from desktop.

Is it because the high voltage cause some surge, so PSoC reset itself? Is there any way to solve this problom?

Please help me. I spend a long time but cannot solve it. Thank you very much!

The usual way would be to proof your suspicion or to exclude it.

Standard is using an oscilloscope, connect to PSoC GND and VCC, measuring AC and looking for spices when the relay triggers. Probably (Test that, too) there are spikes even when the relay switches no load. If switching the load is the cause a very elegant solution could be to perform switching when the voltage is (near) zero.

Bob

Two potential problem areas -

1) If load generated switching noise you have to split grounds to make

sure load current does not generate IR drop logic signals back into PSOC

by raising a GPIO pin. As well large currents imply large magnetic fields,

so single turn loops created by layout practices create transformer coupling

back into GPIO. Additionally you can have e field coupling via parasitic C be-

tween load current traces and a GPIO pin. Where you can afford to burn power

terminate GPIO inputs in low Z to reduce coupling.

2) If relay actuator coil transients, generally speaking its relay coil turn off that produce

large transients. Make sure you have a reasonably fast diode across coil to handle

back emf. Diode must be rated for max coil I. DSO can be used to confirm diode

speed is clamping.

Some useful info on layout practices -

www.cypress.com/

Regards, Dana.

Another thing to look for are drops in the supply voltage - maybe the relais just need too much current so the PSoC loses power. This can be resolved by using proper decoupling capacitors on the PSoC power lines.

The best bulk caps to use these days are polymer tantalums, they

have a f vs esr curve much better than regular tantalums, and much

less C degradation with applied V.

And as always a good ceramic .1 uF (some cases also a .01 uF as well) in

parallel with bulk cap. MLC cermamics pretty good for this.

Regards, Dana.

Hi All,

Thank you very much for your help!

I did add diode with the relay.

I think it is possible due to the chip power drop. i use regulator to regulate 12VDC to 5VDC. The V5.0 is connected to PSoC chip VDDD, and also it is power supply of the relay. While in USB communication connector, there is a Schottky diode also connect to V5.0. I am not sure whether this cause the problem. Now i have removed the schottky diode.

I do not think the Schottky diode was at issue, and it is used to isolate the Vbuss

from other power sources, eg. from back feeding Vbuss and forcing Vbuss out

of regulation.

I would advise leave that diode in place.

Regards, Dana.

Hi dana,

Thank you for your reply :)

Sorry, just to confirm, the Vbuss you mention, is USB gnd?

I removed the diode connected to V5.0, since i thought it is used to supply power to the chip. is this understanding correct?

Vbus is USB self powered supply buss, 5V.

www.cypress.com/

Regards, Dana.