A7 A6 A8 A10+S + GND - –S
PROGRAMMING
R
L
RESISTOR
Figure 3-4.
Remote Resistance Programming
3-21 To maintain the stability and temperature
coefficient of the power supply, u se programming
resistors that have stable, low noise, and low
temperature (less than 30ppm per degree Centi-
grade) characteristics. A switch can be used in
conjunction with various resistance values in
order to obtain discrete output voltages.
The
switch should have make-before-break contacts
to avoid momentarily opening the programming
terminals during the switching interval.
3-22 Voltage Programming (Figure 3-5). Employ
the strapping pattern shown on Figure 3-5 for
voltage programming.
In this mode, the output
voltage will vary in a 1 to 1 ratio with the pro-
gramming voltage (reference voltage) and the load
on the programming voltage source will not exceed
25 microampere.
A7 A6 A8 A10 +S + GND - -S
REFERENCE
VOLTAGE
Figure 3-5. Remote Voltage Programming
3-23 The impedance (Rx) looking into the external
TM 11-6625-2965-14&P
programming voltage source should be approxi-
mately 1000 ohms if the temperature and stability
specifications of the power supply are to be main-
tained. The programming accuracy is 1% of the
programmed voltage.
3-24 Methods of voltage programming with gain
are discussed in Application Note 90, Power Supply
Handbook; available at no charge from your local
Sales Office.
3-25 REMOTE SENSING (See Figure 3-6)
3-26 Remote sensing is used to maintain good
regulation at the load and reduce the degradation
of regulation which would occur due to the voltage
drop in the leads between the power supply and
the load. Remote sensing is accomplished by uti-
lizing the strapping pattern shown in Figure 3-6.
The power supply should be turned off before
changing strapping patterns. The leads from the
+S terminals to the load will carry less than 10
milliamperes of current, and it is not required that
these leads be as heavy as the load leads. How-
ever, they must be twisted or shielded to minimize
noise pick-up.
CAUTION
Observe polarity when connecting the
sensing leads to the load.
R
L
A7 A6 A8 A10+S + AND– –S
Figure 3-6. Remote Sensing
3-27 For reasonable load lead lengths, remote
sensing greatly improves the performance of the
supply. However, if the load is located a consid-
erable distance from the supply, added precautions
must be observed to obtain satisfactory operation.
Notice that the voltage drop in the load leads sub-
3-3
