TCA9803: VILc and IILc

Yusuke Mukuno

Part Number: TCA9803
Other Parts Discussed in Thread: TCA9800

Hi Expert,

I want to confirm about external device low level requirement connected B-side. Is may be basic question.

Datasheet is descried as below,

The IILC parameter is the minimum amount of current that the external device must sink from the TCA980x in order for the TCA980x to accept the low on the B-side. In order for the TCA980x to accept a low on the B-side, both VIL and IILC parameters must be satisfied. In an idle bus condition (both A and B sides are high), meeting the VIL threshold with an external device pull-down meets the IILC requirement, since the pull-down has to sink the entire ICS (current source value) current before the voltage on the pin falls.

Is it meaning, the external device should have sink current ability higher than Ics for driving from idle bus condition to low level?

Or, Is it okay over IILC?

For example, in case of the external device has IoL=3mA sink current ability.

We cannot use TCA9803, because Ics typ is 3.3mA. or we can use TCA9803, because IILC is 1000uA(min). which is correct?

Also, could you please let me know the maximum value of Ics for each TCA9800/1/2/3?

Thanks

Muk

over 3 years ago

+1 Clemens Ladisch over 3 years ago

Guru 244020 points

The external device must be able to sink a current of I_ILC with a voltage drop no larger than V_IL. The I²C specification requires at least 3 mA with at most 0.4 V; all TCA980x devices are designed to be compatible with that.

I_CS specifies the strength with which the TCA980x pulls up an idle line. The external device indeed must be able to sink this current, but there is no requirement on a corresponding voltage drop. Devices that can sink 3 mA with 0.4 V will be able to sink 3.3 mA with a slightly higher voltage drop; this is no problem, even if the external device does not specify this.

There is no specified maximum for I_CS because it is not necessary for interoperability.