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pnndra
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Joined: 2014-06-17 10:05
IO Voltage

Hi,
from data sheets i can't understand clearly what is the IO pin voltage in the various configurations. do i understand correctly that IO voltage is always the same as VBAT? is this true also in BOOST mode where we power the unit from VBAT1V?
in our application we're aiming at two different configurations:
1) 3V coin cell into VBAT3V and chip in buck mode. here we need 3V I/O
2) 1.8V supply from external LDO into VBAT1V and chip in boost mode. here we need 1.8V I/O

can you please confirm assumptions are correct?

let me also add that there is some confusion on the supply rail startup issue. from data sheet it turns out that if supply voltage is below 2.5V the OTP copy process may be unreliable. now, in boost mode, i see from data sheet that DC-DC voltage is still 1.41V and if i understand correctly there won't be any voltage over 2.5V hence the OTP copy may still be at risk, but this would be common for every boost configuration...
finally, if boost DC DC output is 1.41 V and input is 1.8V maybe it's not goig to be a boost but a buck configuration... isn't it?

thanks,
Dario

Device: 
MT_dialog
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Last seen: 2 weeks 3 days ago
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Joined: 2015-06-08 11:34
Hi pnndra,

Hi pnndra,

When the device is in Buck mode the the IO-level as output is VBAT3V. When the device is operating in Boost mode the IO-level as output has VBAT3 or VBAT1V which is selectable by API.

The Boost convertor will produce the proper voltage, when the supply to that convertor is sufficient (in Boost mode 0.9 to 2.0V), it will react on that by giving 2 stable outputs (VBAT3V and VDCDC) when the voltage to the VBAT3V is higher than 2.5V, the LDO of the OTP will reduce the voltage. The power on the core is always 1.41V.

Thanks MT_dialog