MDBT42Q on coin cell

Tue 2018.11.27

' I'll update the docs to make it very clear'

Thank you Gordon.

'What do you mean by that? The MDBT42 docs page says it accepts 1.7-3.6v range'

'By '2v or so' I meant exactly that'

From the manufacturer datasheet heading 'Information' >> MDBT42Q Datasheet p.20

http://www.espruino.com/MDBT42Q

p.20   http://www.espruino.com/datasheets/MDBT4­2Q-E.pdf

Paraphrased: Power on-chip power-on set circuitry may not function above 60ms power on rise time.

Range 1.7 - 3.6 with 3.0 nominal

Me thinks that @Gordon in indicating by '2v or so' that as the chip functions best at the nominal 3.0 voltage, and as when using a coin cell as a supply source, that when the battery discharge threshold is significantly below nominal, that the power on rise time becomes much worse (longer) such that the chip is unable to set itself up correctly as power is applied; and that the coin cells ability to maintain a sustainable working voltage within range is severely compromised. So effectively the battery voltage droop is the issue before the lower limit is reached. Having a stable regulated supply, might allow the chip to function down to that 1.7v limit, but the manufacturer is suggesting a 3.0v optimal value.