BQ27Z746: BQ27Z746YAHR

Gopika Raj V S

Part Number: BQ27Z746
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

Hi team,

We are using the fuel gauge BQ27Z746YAHR in our new design. Currently we are in a trouble and this fuel gauge is not providing output at the PACK pin when we connected a 1500mAh, 3.7V Li ion battery. We have found that the FET is not getting the appropriate gate voltage. So that charging or discharging is not going on and the FET is off. When we connected the battery across the BAT pin of battery charger IC (BQ25628ERYKR) our SOC is working properly. Could you please answer the below queries?

What is the default state of this FET? Do we need to program this fuel gauge to detect the battery charging and discharging?

6507.Image.pdf

over 1 year ago

0 Adrian over 1 year ago

TI__Mastermind 37761 points

Hello Gopika,

Can you verify on the gauge side that the FETs are on. You will need to check the Operation Status A register. If the FETs are on, the CHG and DSG bits should be set high (red). If they are off, then the CHG and DSG bits will be set low (Green).

Regards,

Nick Richards

0 Gopika Raj V S over 1 year ago in reply to Adrian

Intellectual 360 points

Hi Nick,

FET is off. Could you please verify from design side?

0 Adrian over 1 year ago in reply to Gopika Raj V S

TI__Mastermind 37761 points

Hey Gopika,

In terms of the schematic you sent, the connections to the FETs looks fine. I am interested in seeing what BQStudio is showing. Can you send me a log file so I can check the status of the registers.

Regards,

Nick Richards

0 Gopika Raj V S over 1 year ago in reply to Adrian

Intellectual 360 points

Hi Nick,

Thanks for the reply.

We have no evaluation board to check this with the BQStudio. Could you please say what will be the other option to check this? Can we access this using the MCU if so can you please explain in detail? What will be the default status of this fuel gauge registers when we buy this? We are not able to know how it works.

0 Adrian over 1 year ago in reply to Gopika Raj V S

TI__Mastermind 37761 points

Hey Gopika,

The default values should be where the FETs are off. This document talks about gauge communication https://www.ti.com/lit/an/slua801/slua801.pdf

I would recommend sending the CHG FET toggle and DSG FET toggle commands to turn on the FETs.

Chapter 13 also talks about gauge communication protocol. https://www.ti.com/lit/ug/sluucw8/sluucw8.pdf

Regards,

Nick Richards

0 Gopika Raj V S over 1 year ago in reply to Adrian

Intellectual 360 points

Hi Nick,

Now discharging is working fine in our board. Unfortunately discharging is not working.

0 Adrian over 1 year ago in reply to Gopika Raj V S

TI__Mastermind 37761 points

Hello,

Today's a national holiday. We will get back to you tomorrow.

Regards,

TI Apps Team

0 Adrian over 1 year ago in reply to Adrian

TI__Mastermind 37761 points

Hey Gopika,

Gopika Raj V S said:
Now discharging is working fine in our board. Unfortunately discharging is not working.

I'm confused on what's going on here.

Regards,

Nick Richards

0 Gopika Raj V S over 1 year ago

Intellectual 360 points

Hi Nick,

We have toggled the register values and discharging is happening. But we need to know how charging is possible?

0 Adrian over 1 year ago in reply to Gopika Raj V S

TI__Mastermind 37761 points

Hello Gopika,

Did you also toggle the CHG FET?

Regards,

Nick Richards

Power management

Power management forum

BQ27Z746: BQ27Z746YAHR