Drive Current Sufficiency

[gunayburak]

Also do you think this MCU's weak current supplying ports can handle and succesfully drive the A/B/C/INH signal inputs of CD4051 and A/B/C/D/INH signal inputs of 4514 ?

[HenrikOlsson]

I think perhaps we've both misinterpreted the datasheet a little bit.
Look at table 6.5 in this Texas Instruments datasheet. There we can see that indeed the maximum input current is 1.35mA at 3.85V but a little bit further down we can see that an input current of 250uA will still produce a collector current of 100mA while only dropping a maximum of 1.1V.

Input current on CMOS series logic chips seems to be in the uA range so no problems there.

[gunayburak]

Don't you think the current at 3.85 V proportionally should increase at 5V drive voltage..? Secondly do you have any idea with my other question ?

• Also do you think this MCU's weak current supplying ports can handle and succesfully drive the A/B/C/INH signal inputs of CD4051 and A/B/C/D/INH signal inputs of 4514 ?

[HenrikOlsson]

Don't you think the current at 3.85 V proportionally should increase at 5V drive voltage..? Secondly do you have any idea with my other question ?

It might, if it was allowed to but it can't since the output can only source 2mA. If you're worried, why not measure it? Add an external series resistor if you want to be sure that the circuit can't ever pull more 2mA.

Secondly do you have any idea with my other question ?

Please read my previous reply:

Input current on CMOS series logic chips seems to be in the uA range so no problems there.