Re: SMPS will cause spike current ?

On May 24, 5:18 am, Boki <bokit...@xxxxxxxxxxxxxx> wrote:
Hi All,

Our wireless short range communication is in standby mode now,
however, the software is working, should be no anything to do. ( I
want to indicate the s/w level is still alive, but nothing to do )

I got spike current in the duration of standby mode, I can't make sure
that is because NOP command ( or other not really important
commands) in the s/w level or h/w components effect it.

Any idea about read / write a EEPROM value will cause spike current
about 7mA, is it possible ?

Any idea about change a PIO will cause a spike current about 7mA ?

The module work at 1.8V at core chip, however, it accept 4.2V battery
voltage, it should has its own regulator. The PIO output I got is 3V.
The normal normal standby current is 1.5mA range.

Please let me know if I have to input more info.

At least some switched mode power supplies operate in the
"intermittent mode" when lightly loaded - they draw a signifcant
current for a short time, charge up their output reservoir capacitor
to the upper threshold output voltage then wait until it discharges
discharges to the lower threshold.

A really cheap crude switching step-down regulator would always
operate this way - the 4.2V battery charges up the reservoir capacitor
to a certain voltage which is less than the highest output voltage,
storing a certain amount of energy in the inductor in the process.
Once the reservoir capacitor hits this voltage, the input side of the
inductor is switched from the 4.2V down to ground, and the current
through the inductor proceeds to decrease to zero, charging up the
resevoir capacitor even further in the process.

At this point the system designer could elect to open circuit the
input side of the inductor (but this needs a sensor for the current
through the inductor, which costs money) and wait until the reservoir
capacitor has discharged itself to the lower output voltage threshold
before starting to recharge the inductor.

The cheaper solution is to let the current through the inductor go
negative and start discharging the output capacitor until it hits a
threshold voltage somewhat higher than the lowest acceptable output
voltage, and then reconnect the input side of the inductor to the
battery. It will take a while for the battery to increase the current
through the inductor back to zero, and the voltage across the resevoir
capacitor continues to decrease untl you get to this point.

--
Bill Sloman, Nijmegen
--
Bill Sloman, Nijmegen

.

Relevant Pages

  • Re: SMPS, control loop?
    ... If the controller responds slowly (as it must in voltage mode), then the duty cycle will remain constant, pumping more charge into the filter inductor, also ramping up transformer current as well. ... This energy then flows into the capacitor, so voltage keeps rising, a lot, and the controller chokes off the PWM until capacitor voltage falls to a reasonable level, at which point the voltage continues to drop, because it then takes more time to recharge the inductor. ... As long as the peak energy stored in the output capis>> that in the choke, the overshoot is small. ...
    (sci.electronics.design)
  • Re: [BugTraq] Peter Gutmann data deletion theaory?
    ... Secure Deletion of Data from Magnetic and Solid-State Memory ... amplification would quickly move the voltage ... The question is whether the chip could be powered up ... Dynamic RAM involves a single transistor connecting a single capacitor ...
    (Bugtraq)
  • Re: Cap or Second Battery?
    ... Here are some functional differences between a cap and a battery: ... The operating voltage of a cap is defined by the charging voltage, ... depending on the car and condition of the alternator. ... This simply means that the capacitor has the ability to ...
    (rec.audio.car)
  • Re: Capacitor bank pretty well complete
    ... Charge them with line voltage and discharge into ... short the terminals through a coil. ... will make some generous magnetic field, maybe I can shoot an aluminum plate ... A capacitor is the opposite of an inductor. ...
    (sci.electronics.design)
  • Re: Need to fix old valve radio
    ... to drop the line voltage from 230V to 115V. ... capacitor rated 30 uf or larger, ... If both pins of the capacitor are ... Is the sound clear at low volumes? ...
    (sci.electronics.repair)