BQ20z65 Shutdown with current not zero

Maximilian,

I asked which device you are using in your other post. I see it is the bq20z65 now. Please attach your schematic, so that I can check it for problems. The pcb layout can also be helpful.Gerber files will do.

Regards
Tom

Tom,

we are using the bq20z65 in conjunction with a MSP430. The MSP shall control the bq via SW or I/O ports, in order to reduce the power consumption. Therfore we want to force the bq in shutdown mode.
Bq and MSP communicate via SMB.

Is there a method to set the bq in shutdown mode without fulfill the condition given in the TRM para.2.8.5?
E. g. set the REG25 or REG33 to GND!?

Roland,

Those are the only provisions to place the device into Shutdown mode.

Regards
Tom

Tom,

We have changed our hardware layout to achive zero current i.a.w. slua534. Now it works.

Thank you very much for your support.

Roland

Hello

I had a small doubt regarding bq20z655-r1 gas gauge. I want to use this in an external battery pack application and there is no MC or FPGA (basically no communication with gas gauge) in my application. Is it possible for me to switch the gas gauge in sleep and normal mode by hardware?

I did go through the technical reference of bq20z655 (SLUU493) and the EVM (SLUU697) guide. The technical reference says it will enter sleep mode if [NR]  is set to 0 and input to PRES be high whereas the EVM guide shows a picture saying that when PRES input pin is high it enters sleep mode thereby providing 2 contradicting answers. Can someone help me?

Thanks

Shravan Raghu

Shravan,

reference manual says

so note

1) that the pin on the chip is actually /PRES and for PRES to be 0 the chip pin /PRES must therefore be logical high.

2) When the pack is not inserted the /PRES line gets pulled high by the hi-z 100K pull up to TOUT whenever the /PRES line is being sampled. 

3) When the pack is inserted the /PRES pin is held low since the sys pres input line is pulled low on system side and  it pulls low stronger than the 100K can pull high.

So what this says is that if you have a removable pack you can only sleep if the pack is removed and /PRES gets pulled high to make PRES =0. A removable pack can never sleep once it is inserted into the system. This is how it was defined and at first sight causes the confusion as it is maybe not what you might expect.

The EVM manual just says

So it is just saying to test sleep mode you must disconnect the sys pres pin , i.e. so it is no longer pulled low to PACK-, in which case the pack will think it is removed and  as described above the actual /PRES pin will be pulled high by the 100K to TOUT, in which case PRES shall be low.

So everything is consistent.

Note if NR=1 then that means it is in non removeable mode and it does not matter what /PPES or PRES is doing and it does not affect entry into sleep mode. So the note in EVM user guide really only applies if NR=0,  but as this is the default mode it is sensible advice in case it has not been changed