DC/DC switching regulator for ZigBee module

[nickagian]

I am supplying a SPZB250 ZigBee module with 3.3Vdc from a DC/DC buck/boost switching regulator (TPS63031). The input to the regulator is a Li-ion battery with 3.6V nominal voltage. The device is operated as a ZigBee end device. The problem that I face, is that sometimes when the device connects to the ZigBee network it experiences reset.

I monitor the current drawn from the battery and while the module is active and connects to the network, the current drawn is around 50mA. Sometimes, after the connection has been established and while idle (or even while transmitting) the current drawn falls to around 0.8mA, which is the sleep current of the device.

Can this behavior be caused by instant drops of the supply voltage from the regulator? Or, perhaps the switching current from the regulator produces noise that causes this reset? Can anyone give me a hint on this? Have in mind that this is the first time I use a switching regulator in my designs, so I do not have any experience at all.

 

[crutschow]

Switching noise can cause glitches in circuits if not properly decoupled. Do you have a decoupling capacitor across the ZigBee module power input lines (0.1 ceramic with short leads)? How much switching noise do you see on the power? (Do you have an oscilloscope?)

 

[nickagian]

Hi crutschow and thanks for your answer!

In fact I have put two capacitors at the input Vdd of the ZigBee module, one 10uF electrolytic and one 0.1uF ceramic. The truth is, nevertheless, that at the PCB they are not located exactly at the power pin of the module. Do you think the distance could be of importance? I could solder an additional 0.1uF ceramic directly on the pin and test the behavior again. Although I have access to oscilloscope, I have not yet used it. I think I should do it today. How can I understand how much switching noise exists? I should check the variations of the voltage supply I guess?

 

[dknguyen]

Yes, lead distance is important, as is the area of the loop formed by the ground and power wires/traces between the two. A radio circuit would be particularily sensitive to all this.