Internal Resistors in ICs

[J_M_B]

Hi

What does everyone think of relying on internal pullups/pulldowns in ICs?
I have motor driver with internal 30K pulldowns on the enable lines. Can I trust them?
I worked with a very experienced digital design engineer who told me he didnt place much faith in them.
I've heard its difficult to manufacture internal resistors in ICs to specific values.

Do we think the 30K figure is reliable?
Anyone had any problems using internal resistors?

Any thoughts would be appreciated

 

[chuckey]

If you do not trust the internal 30K resistors and put external ones, what are you going to do about all the other internal resistors?
FWIW, 30 years ago my Brothers Sony colour TV lost its sound. The problem was with the sound demodulator IC. An internal series resistor had gone open circuit. For some reason the IC manufacturers had brought both end of it out on pins. So I put on an external one and VOILA! the sound worked again.
Frank

 

[KlausST]

Hi,

a simple answer: read datasheet.
Either you will find the range (min max) of the 30k resistor,
or you find the (min max) current caused by the resistor.

they may have a huge tolerance: -50% +100% is not unusual.

If you find the values in the datasheet you can rely on them.
In case they are not given, i´d call the datasheet "not complete".

Klaus

 

[J_M_B]

Hi

Thanks for your message

Yes, datasheet is incomplete. There is only 30KOhms figure mentioned. In another section it shows an internal schematic but with 80K resistor.
Ill look for more info, thanks for the input

Jamie