BQ27520-G4: I2C t(BUF) bus free time spec too big (66uS)

Cage Chen21

Part Number: BQ27520-G4

we planing to use a common I2C bus as 400KHz clock speed for gauge IC and others accessories, The bq27520 spec shows it can support high speed clock up to 400KHz but bus free time spec is 66uS(min), does it correct? the I2C spec should be 0.5uS (min), please help to confirm does spec correct? and can bq27520 work on 400KHz I2C bus clock? why the gauge IC bus free time spec so big?

over 6 years ago

0 Onyx Ahiakwo over 6 years ago

TI__Guru* 76230 points

Hi Cage

The 66uS is delays between commands. We have many customers that have used the device with 400kHz just fine.

thanks

Onyx

0 Cage Chen21 over 6 years ago in reply to Onyx Ahiakwo

Intellectual 365 points

Dear Onyx

As I stated, we have few device on this I2C bus, here only TI's gauge IC is 66 uS longer than standard 0.5uS, we are worried it may cause communication bus abnormal/fail. does your customer used 2 or more salves on a bus with 400KHz speed?

0 Onyx Ahiakwo over 6 years ago in reply to Cage Chen21

TI__Guru* 76230 points

Hi Cage

Yes, we have had customers use more than 2 slaves on a 400khz i2c line.

thanks

Onyx

0 HungTa Lee over 6 years ago in reply to Onyx Ahiakwo

Prodigy 10 points

Hello Onyx

Very thank you for your replay

I am Cage's colleague

in my platform system , Unable to meet Tbuf >66us specification, because CPU chipset follow NXP's I2C standard

According to my previous experience, the longer delay time is mostly because the IC's I2C port passes through the buffer.

Is the TI's Fuel Gauge same as this (internal buffer delay time of fuel gauge chip)?

Is the Tbuf necessary to meet the requirements?

If not need Tbuf specification ,Is it possible to cause read / write error?

0 Onyx Ahiakwo over 6 years ago in reply to HungTa Lee

TI__Guru* 76230 points

hi Hung,

Without that delay you may have watchdog resets of the IC. I wouldn't recommend using less than what the TRM specified.

thanks

Onyx

0 user3570217 over 5 years ago in reply to HungTa Lee

Prodigy 160 points

Hello

the same promble i have encounter by use the i2c to drive at24c64, Have you solve it?

0 Onyx Ahiakwo over 5 years ago in reply to user3570217

TI__Guru* 76230 points

Pls start a new thread about and elaborate on the issues you face.

thanks

Onyx

Power management

Power management forum

BQ27520-G4: I2C t(BUF) bus free time spec too big (66uS)