FM24C16B follows the I2C-bus specification on the specification of tLOW (Clock LOW period), So tLOW has only a min limit.
However, you can consider the max is indirectly determined by its tHIGH or Clock HIGH period. Condition is that system timing must satisfy tLOW + tHIGH <= 1/fSCL; As long as this condition is met, tLOW or tHIGH max can be adjusted to any value.
fSCL can be 0Hz to 100KHz in standard mode, 400KHz in fast mode, 1MHz in fast mode plus, and is determined by master side, so tLOW max can be any value as long as tHIGH min timing is satisfied.
In your case, tLOW of 20us is ok as long as tHIGH min timing is satisfied.
Also, FM24C16B doesn't support clock stretching.
Thank you for your reply.
It was MCU port control, not I2C master hardware.
Probably because the MCU is doing another process, the time is extended.
I understood that there was no problem as FRAM.