STM8TL52 current consumption in Halt mode about twenty times higher than expected

[Ted Jackson]

Hi. I'm using an STMTL52F4 20-pin MCU that I've programmed to immediately enter HALT mode on startup with the halt() command. Although the documentation says that the chip consumes only 0.4uA in this state, when I put a multimeter in series with the chip's VDD pin, I'm seeing about 20 times that current going in. I know that the chip consumes more current while debugging with STVD via the ST-LINK/V2 / SWIM interface, so I'm testing immediately after a power-on reset (with the ST-LINK still attached). Am I missing something? The thing is, I observed the chip consuming about 1uA earlier, but I can't figure out what I'm doing differently now. Does the chip consume more power with the ST-LINK attached? Thanks.

[Ted Jackson]

The problem may be just that fact of dealing with such tiny currents, the leakage of capacitors used and the shortcomings of relatively cheap multimeters. Using an old analog (dial indicator) amp meter shows as little as ~12uA and as much as ~38uA. A digital handheld shows as little as ~108uA and as much as 288uA. A further test with the digital meter reads ~110uA in halt() right after power on, ~300uA in the LowPower Example program from the STM Touch Library, ~290 in halt() right after that and then ~108uA in halt() following a power on reset). But I have still to see anything close to the ~0.4uA so far. Part of the problem may be in how to get the chip in a minimum current consumption state beyond just the halt() instruction - peripherals, etc.

ST obviously has great depth in its engineering capabilities. But it's depressing to see such a shallow community support base (at least for the STM8's). I guess ST is oriented towards big business with the basement entrepreneur type kinda left out in the cold. Guess that makes economic sense, but it's still a little depressing.