Lithium battery for nrf51822

[Tizana]

hi,

I'm designing a board with nrf51822 chip. this board work on 2450 lithium rechargeable battery and it contain an MCP73831T circuit which is responsible of recharging the battery.

the MCP73831T circuit contain a STATUS output which indicate the charge STATUS. this output i want to use it as an input to the nrf51822 in order to detect the charging status level.

this output had 3 stats, low, high and high impudence.

my questions :

1/is there anyway that the nrf51822 input can detect the High Z level ? if not how can i do to read these 3 status ?

2/ the MCP73831T chip is working on a different voltage level with the nrf51822 ! the nrf51822 is powered through a step-down DC-DC converter and not directly through the battery.

so this is why i'm trying to figure out a way to connect the STATUS signal from MCP73831T to the nrf51822 .

thx,

[AmbystomaLabs]

I think you can do something as below. You will need to go through the ohms law stuff to figure out precisely what is needed. Also, you need to look at the ADC spec to see how big C1 needs to be. But as long as the resistors are in the 500K range the leakage will be low. Basically, high Z gives 1/2 nRF VDD, Status low gives 1/3 nRF VDD and status high gives a little above 1/2 status VDD (again you need to do the ohms law stuff).

[bjorn-spockeli]

@tizana: You should take a look at the Measuring Lithium battery voltage with nRF51 blog post.

[AmbystomaLabs]

Tizana's question is about interfacing the status port on a Microchip LiPo charge controller to the nRF. It has an odd interface with one of its status indications given by high impedance on the port. Though Tizana will probably eventually ask about reading the LiPo voltage with the nRF.