Beware of really low Iq LDO regulators. They often do not work well with DW1000 due to sudden changes in current demand. The super low Iq LDOs use P channel FET pass elements which have poor transient response times, that is, they take longer to notice an output voltage drop and recover. In some cases, this can damage transmit packets as the voltage fades during the packet time. Pay attention to the transient response characteristics when selecting an LDO.
In many cases, a switching regulator can be a better choice even given the relatively low voltage drop from the battery.
Sounds like DW1000 is in IDLE state (crystal operating, PLLs locked). Do you think you have the DWM1001 operating in SLEEP or DEEPSLEEP state? To get the battery life you expect, you will have to be in those states between events. I don’t know what the Decawave supplied code does in this regard.
You have a LOT of battery energy using an 18650 cell. With an LDO to 3.3 volts, you get to use about 365 uA average current. Given you are using 3 anchors, that implies TWR location, so you need to transmit once, receive 3 times, and transmit once again to complete a location.
Putting some very round numbers on that:
995 ms: sleep time, ~20 uA?
3 ms: crystal spin up time, 4 mA
200 us: TX first packet: 70 mA
1 ms: RX 3 packets: 140 mA
200 us: TX last packet: 70 mA
200 us: clean up and sleep: 10 mA
Add it all up, assuming 1 Hz rate, and the average current draw is 202 uA. Net output is 32 million locates during that time to cover one full year. Assuming room temperature, the 18650 cell will also self discharge some amount, say about 20-30%, so you don’t get all of it, either, but there should be enough to do a year.
At this level of power optimization, little things mean a lot. Don’t leave pins floating (CMOS pins at half input cause current). Don’t drive pins into powered off devices. Beware of regulator feedback dividers and how much power they use. Design everything so that pull ups or downs are not drawing current in inactive states. You have to carefully use sleep modes on the processor. And so forth.
Low power is mostly a software/protocol thing once you’ve done all you can with the hardware.
Mike Ciholas, President, Ciholas, Inc
3700 Bell Road, Newburgh, IN 47630 USA
+1 812 962 9408