>> >> Interesting, obviously, removing the bottom resistor from
>> >> the divider would increase the speed of rising (assuming
>> >> inputs would tolerate it). But, according to your logic/formula
>> >> removing the bottom resistor would increase impedance
>> >> and, thus, decrease the speed of rising.
>> >
>> > Not exactly. With two resistors the impedance is 1.2k and
>> > with only one it's 2k. But the equivalent voltages are 3.3 and
>> > 5 respectively. If you are driving logic with TTL(1.2 volt) thresholds
>> > the rise times will be very close.
>>
>>TI CC1101 is not TTL.
>> >From its datasheet:
>>4.8 DC Characteristics
>>Logic "1" input voltage (VDD-0.7V) to VDD
>>
>>For your 3.3V it will be >=2.6V.
>>Obviously the presence of the bottom resistor of the divider would
>>slow the signal rising to that level, the times with/without the
>>resistor should not be "very close".
>
> Well, if you connect the same upper resistor to 300 DC it will have
> an even faster rise to 0.7* 3.3 VDC, but it's precisely as pointless
> a comparison as your example

In this thread generalization is prohibited by some. It would be
better to say "may be pointless to some under some special
circumstances".


> since it violates the abs. max. ratings of the chip and
> thus is not a valid solution.

I said: > (assuming inputs would tolerate it).


> Do you know the simple equation that the v(t) follows?

You may wish to ask Olin. His favourite job interview question to ask,
if I am not mistaken, is about the equation of a voltage on a
capacitance connected to a DC source through a resistor.
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