bq34z100 ACK too late in I2C

Hello All,

I use a bq34z100 in I2C, host is a MCU from ST./ In the bq's datasheet, 

http://www.ti.com/lit/ds/symlink/bq34z100.pdf

I can read on page 7 : t(RSPS) max = 950µs but in real life, I measured 15ms

What is the maximum value for the bq send ACK to the host ?

Regards,

BHD