[vna] Temperature od DDS

[tom.mcdermott4 at sbcglobal.net]

Yes, this is normal.  During assembly the IC must make good thermal contact
with the
PC board because the circuit board itself is the heatsink for the DDS IC.
The same
is true for the voltage regulator IC. Both of these IC's have a metal slug
on the bottom
that provides a low-thermal-impedance path to the board.
 
If you have good thermal contact with the board, then the temperature of
each IC will be OK.
If during assembly you were not able to achieve good thermal contact, then
an top
surfact heatsink could be needed.
 
    -- Tom, N5EG
 
 
 
-----Original Message-----
From: vna-bounces at lists.tapr.org [mailto:vna-bounces at lists.tapr.org] On
Behalf Of Mariusz Wyszynski
Sent: Thursday, August 24, 2006 10:25 AM
To: vna at lists.tapr.org
Subject: [vna] Temperature od DDS


Hi,
I have finished assembly VNA. 
When I connect power suply, the DC current is about 480mA, then I start PC
programming and DC current is increasing to about 980mA.
Temeperature of DDS (IC4) is inreasing from 28 to 70 degrees of Celsjus. 
Is it normal?
Should I use radiator?
VNA is working because I did detector and fixture calibration (now I am
using radiator and fan against of overheating DDS)
 
 
73 Mariusz SQ5MGG
 
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