BQ20Z655-R1: Charge Enable doesnt work.

user5503575

Intellectual 800 points

Part Number: BQ20Z655-R1

Hi, I am trying to produce batteries with bq20z655-r1.

But while I am trying to upload my rom file to batteries, some of batteries doesnt turns chg fet on.

When I send 46x0006 or It Enable(21), chf fets turns on 2 second and turns off again. Dsg fets works normally.

Also some of batteries works normal but when I try to discharge them, chg fets stays off.

I think that the reason is CE pin. I left that pin float. Is it a problem? Do I have to pull it down?

In data flash-charge algorithm-chg inhibit threshold is 10ma and the time is 0 second. Do I have to set threshold to 0mA?

I am confused because some of batteries works normal, some of batteries works weird. Does CE pin stay unstable situation because of left float?

over 5 years ago

0 Andy Liu (BMS) over 5 years ago

TI__Guru 52115 points

First of all, bq20z655-r1 is a bit old device and I would NOT recommend it for new designs. Also, if I remember correctly, its EVM is already obsolete. I would suggest you use bq40z50-r3 since it a new device and have good EVM and software support.

I would suggest you try disabling the CE pin by setting the Chg Inhibit Threshold to 0.

Andy

0 user5503575 over 5 years ago in reply to Andy Liu (BMS)

Intellectual 800 points

Sorry, I accidentally clicked that this comment resolved my issue.

I have already tried to set threshold 0mA. But there is still problem. I am thinking to connect CE pin to Gnd. What do you think about CE pin ?

0 Kang Kang over 5 years ago in reply to user5503575

TI__Mastermind 24870 points

Hello User,

CE is chip enable. Can you make sure it is connected similar to the datasheet reference schematic?

0 user5503575 over 5 years ago in reply to Kang Kang

Intellectual 800 points

That is Charge Enable pin. And on my design, CE pin is float now. In schematic, it looks float. But I noticed that pin connected to ground on EVM schematic.

Is it problem? Can I left that pin float?

0 Andy Liu (BMS) over 5 years ago in reply to user5503575

TI__Guru 52115 points

A floating pin is not preferred. I would suggest you follow the EVM schematic so that the CE pin doesn't float.

Andy

0 user5503575 over 5 years ago in reply to Andy Liu (BMS)

Intellectual 800 points

Thank you Andy,

I will edit it. But I already ordered some PCB's and I would like to use it. Is it possible to see any unstable state about CHG mosfet due to that pin?

0 Andy Liu (BMS) over 5 years ago in reply to user5503575

TI__Guru 52115 points

We all have to work from home due to COVID-19. As I mentioned before, the bq20z655-r1 EVM is already obsolete and I cannot get hold of an EVM to check. I would suggest you modify one PCB board by yourself to check if the CE pin is the cause.

Andy

0 user5503575 over 5 years ago in reply to Andy Liu (BMS)

Intellectual 800 points

Thank you Andy.

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BQ20Z655-R1: Charge Enable doesnt work.