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current ls factory adjusted to wlthln 2%
,,r'
3. 3,;;A.
If
greater programming accuracy ls required, lt'may
be achieved by changing resistor R39
a~
discussed
ln Paragraph 5-70.
3-20 To malntaln 'the stablllty and temperature
coefficient of the power supply, use programming,
resistors that have stable; low noise, and low
temperature (less than 30ppm per degree Ce~tl-:, :,,, ,
I
grade) characteristics •. A switch can bel us.
'Vn'',
\.,!,
conjunction with various resistance values' \tlor,Jo?/
to obtain discrete output voltages. The ~witch ., "
1
should have make-before-break,contacts
1
to avoid
momentarlly opening the programming terminals
.during the 'switching lnterva I.
Figure 3-4. Remote Voltage Programming
·
· (Constant Voltage)
3-21 Voltage Programming (Figure 3-4). Employ
the strapping pattern shown on Figure 3-4 for volt-
age programming.,'
lil
this mode, the output volt-
age will vary In a 1 to
1
ratio with the programming
voltage (reference voltage) and the load on the
?rogrammlng voltage source wlll not exceed 20
mlcroarriperes.
3-22 An Impedance matching resistor of approxi-
mately 1000,,. should be connected In series with
the voltage source to maintain the temperature and
stablllty specifications of the power ~upply.
3-23 Methods of voltage programming with gain
are discussed In. Application Note 90, Power Sup-
ply Handbook; avallable at no charge from your
local\1 Sales Office.
3-24 REMOTE PROGRAMMING, CONSTANT CURRENT
3-25 Either a resistance or a voltage source can
be used to control the' constant current output of
the supply. , The CURRENT controls on the front
panel are disabled according to the following pro-'
cedures.
3-26 Resistance Programming (Figure 3-5).· In
this mode, the output current varies at ·a rate de-
termined by the programming coefflclent (600 ohms/
Ampere)., .The programming ':'oefflclent Is adjusted
'
'
r.·i:r.:·r:,,·
'H·il • J:iitt-"ir!~J:.·~-- "'' •.,,-..
~
r
'"'F:tf,"'-f"'~J!:'0.:·
~··•t.'·'· ''•,,
1 ·\
"\'>'<'a••~\."'
~/!""""'
'r./rt
1;\~Wi;:~VJ/"
~'\""''!Si'
t.t:Ll)t'l{,~)'.tf ,fi~r
1
t~·,~'\(
1
'~;p•,._·(J
·!.''
1
~\1S(t8:i;~
~
.. ,.. ,,,,,
' ' ,,.
. '
.,t '
' '
•,
.
,,,,f,,),,
i;:j\j_,\' : \;:.•1' . ,··._
'
_"·:. ' . -~.
~
CZ,
·t.i_;:;;_1_(·,1
'
'
I
._,
'
":J
_'
' '
\1 ,
.\
t
J
Figure 3°-5. '.t\emote Resistance Programming
'
'
\
..
'
/
,,(Constant Current)
'jf
I
:-
· ,
l
for an ac;curacy of 6% at the factory.,
If
greater
programming accuracy Is required, It may be a-
chieved by ahanglng resistor R41 as outlined, In
Paragraph 5-72.
,
.
,
I
i
'·
'
'
'
'
'
'
, ~-27 ,Use stable, low noise, low tP.mperature co-,
efflclenl! (less than 30ppm/°C) programming resis-
tors td malntaln the power supply temperature co-:'
efficient and stabllity speclflcatlons. · A switch /
'
'
'
,fllay·',e used to set,dlscr~te values of output cur-
rent •. A make-before~break type of switch should
be used since the output cun;ent wlil exceed the
'maximum rating of the r,bwer supply lf the switch
I
'
I
'11
1
-
'
l
contacts open durlng,the swltchlng lntei;val.
./ '
i)
i
.
'1
' , ' i \'
I
I,
I'
Ii '·
,
1
_...._ _ _ -CAUTION-----
/1 ;'
! '
'
If the programming' terminals
(AZ
and
A4) should open at
any
time during
I
\,
'
I '
•
1 \
thls mode, the 9utput current wlll rise
to
a
yalue that may damage the power
supply and/or thc:load. To avoid this;
possibility, connect a 200 ohm ~csls-'
tor across the programming terminals.
LiJ<e the programming resistor, this
'
resistor should be of the low noise,
low teinperature coefflclent type,
i
'
'
I
,
,
/
• ,
3-28 Methods used to voltage program a power
supply with gain are discussed in Appl!cutlon Note
90, Power Supply Handbook;,available'at no charge
from ,your local rEj , Sales Offke.
i · ·
·
'
I
.
3-29 REMOTE SENSING (See Flgute 3-6)
. · . .
. I
. · ..
3-30 Remote sensing ls used to maintain good
regulation at the load and reduce the degradaUon
of regulation which would occur due to the voltage
drop in the leads between the power supply and
, the load. · Remote sensing ls accomplished by utl-
' llzlng ~he strapping pattern, shown ln:Flgure 3-6::,
The power supply should be turned off before
changing strapping patterns. The leads from the
+S terminals to the load will carry much loss cur-,.·
3-3
' ' '
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