I received a Torex XC9145B33CER-G evaluation board a few weeks ago and thought that I'd try it out. The EVB PCB is designed for their XC9141/42, XC9145, and XC9147/48 DC/DC converters. This particular board is fitted with an XC9145B33 which has a 3.3V @ 300mA output.
These parts have 3 different footprints available - the PCB is using the USP-6C.
I don't think that you could identify the specific converter from the markings - I'll have to label the EVB in case I ever get one with a different converter.
The salient specs for this part are the ultra low 400nA quiescent current, and high efficiency (~90%) at low current (<10uA). I thought this might be a good converter for low duty-cycle battery powered IoT applications.
Torex has a static dc/dc simulator that allows you to plug in various parameters and see the effect for different EVB configurations. So, I plugged in my EVB and gave it a try.
I'm interested in using either rechargeable 1.2V NIMH or 1.5V alkaline batteries at loads from 100uA to 30mA and the simulator results looked promising. The feature I wish the simulator had was to sweep parameters and output plots.
I decided that I would try using my Nordic Power Profiler 2 (ppk2) to take input current measurements while sweeping the input voltage with a fixed output load to get a sense of the range of operation and efficiency at various loads. I decided to sweep from 1V to 3.3V in 100mV steps. I used loads of 100uA, 1mA, 10mA, and 20mA. I was intially surprised with the response, but it was somewhat repeatable.
100uA
1mA
10mA
20mA
I repeated the sweeps at 100uA and 1mA and also plotted the simulator response.
I mentioned this to the Torex rep and he pointed out the spec for this part calls out a "start voltage" of 1.6V
There is a "Chip Enable" for this part that enables the converter. I had tied it to the input voltage based on what I saw in this table
But futher down the spec
So there isn't a guaranteed enable until CE is above 1.5V - hence the start voltage of 1.6V. I went back and observed the output voltage and sure enough it was not at 3.3V when I was getting the funny current values at the lower input voltages.
The funny current values when the input voltage is close to the output voltage is a different effect, but it would not have affected me because I did not intend to operate at those voltages - just wanted to see what the part would do - BTW the output stayed at 3.3V even with the input current moving around.
Anyway, this part won't work for what I wanted. Torex has other parts (XC9140, XC9110/9111) that are intended for lower voltage inputs that are 10-15% less efficient, but are designed to work with NIMH and alkaline batteries (start voltage ~0.9V). I'm not sure where the simulator puts the CE voltage as that is not a parameter that you can change.
