??? 06/13/05 10:36 Read: times |
#94760 - No worry... Responding to: ???'s previous message |
Musharraf said:
Upon reset, the pins are initialized as high impedence inputs. However, I have read that floating inputs are not a good thing to have in a system (Especially if it is in strong electric and magnetic fields). They aren't floating, they are pulled high by a weak internal active pull-up. And if you don't connect anything to these pins, then they aren't susceptible against noise and interference. The issue with the increase of supply current has to do with the input voltage to internal input gates, which are also connected to the port pins internally: If these get input voltages which are not identical to the supply 'rails', means either 0V or Vcc, then there's an increase in supply current of these individual input gates. This has to do, with the certain topology of CMOS gates, where a PMOS and NMOS transistor are connected between the supply rails, and where a change in input voltage makes the one to partially turn-off and the other to partially turn-on. Especially in applications, where a battery backed-up CMOS RAM is used, even only a slight differ of input voltage from supply rails can make the battery extremely leak! But here we have indeed floating inputs, unless pull-ups or pull-down are connected to each input. But again, with your application you have already pull-ups which prevent such an increased supply current. Kai |
Topic | Author | Date |
Minimizing port pin currents | 01/01/70 00:00 | |
Old threas | 01/01/70 00:00 | |
Thread Vs Reply | 01/01/70 00:00 | |
What would be good | 01/01/70 00:00 | |
for me it does | 01/01/70 00:00 | |
Re: for me it does | 01/01/70 00:00 | |
No worry... | 01/01/70 00:00 | |
but | 01/01/70 00:00 | |
Sorry, I misinterpreted Musharraf | 01/01/70 00:00 | |
low power | 01/01/70 00:00 | |
re | 01/01/70 00:00 | |
TI ? | 01/01/70 00:00 | |
Total agree | 01/01/70 00:00 | |
low power MCUs | 01/01/70 00:00 | |
App notes | 01/01/70 00:00 | |
Any link for low power appnote? | 01/01/70 00:00 | |
Damn all | 01/01/70 00:00 | |
static current? | 01/01/70 00:00 | |
very low frequencies | 01/01/70 00:00 | |
it's not just CMOS | 01/01/70 00:00 | |
Biasing generator for the substrate? | 01/01/70 00:00 | |
flash? | 01/01/70 00:00 | |
consumption overview | 01/01/70 00:00 | |
SiLabs Wins Then? | 01/01/70 00:00 | |
I don't know![]() | 01/01/70 00:00 | |
Do worry! | 01/01/70 00:00 | |
High impedance | 01/01/70 00:00 | |
Battery powered circuits | 01/01/70 00:00 |