[SI-LIST] DC/DC converter output dip
- From: Jean_Pierre.Bouthemy@xxxxxxxxxx
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 6 Aug 2003 11:06:41 +0200
Hi SI experts,
This is a problem more relative to power distribution system than signal
integrity.
On the current design I am trying to debug, the output of a DC/DC converter
(non isolated, 3.3Vin, 2.5Vout) dips from 2.5V down to about 1.5V every 90
ms (around 11Hz resonance).
I am unable to find where it can come from !! This 2.5V supply voltage is
monitored whit a comparator circuit in order to drive Mosfet after the
DC/DC converters on my board. The resistor divider is made with 1K74
(between input+ of aop and 2.5V) and 2K43 (between input - of aop and
ground). A 10nF capacitor is used between both resisitors. A strange
phenomenon is that when i remove the 1K74 resistor (thus the 2.5V is no
more monitored), the 2.5V output is then OK (no more dips !!). Just like if
the comparator circuit disturbs my DC/DC output ! But why?
An other information that could help you is that the output capacitors are
100nF in parallel with 4.7uF in parallel with 100uF (I have the same caps
on other DC/DC converters and I have no problem).
Has anybody ever seen that?
Thank you for your help.
Regards.
Jean-Pierre
--------------------------------------------------------------------
Jean-Pierre BOUTHEMY
Hardware Design Engineer
ALCATEL - Mobile Networking Division (MCG)
Mobile Core R&D
+33 (0)2 99 26 08 18
mailto:jean_pierre.bouthemy@xxxxxxxxxx
--------------------------------------------------------------------
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
