Scientific 5000 Series, Manual, Page: 247 / 360

APPENDIX B
MODEL 5000 SERIES MANUAL
Version 1.23
13-7
Figure 13-2 LM317 Adjustable Voltage Regulator
Sample Set-Up and Programming for an LM317 3 Terminal
Regulator
Step 1: R1, R2 Select:
To set output voltage to 5 V
R1 drop = VREF = 1.25 V
R2 drop = 5
– 1.25 = 3.75 V
R2/R1 ratio = 3.75/1.25 = 3
Choose R1 = 249
Ω (per Mfg)
Therefore R2 = approximately 750
Ω
Attach these resistors to terminals on Regulator Adaptor
Step 2: Regulated Voltage Out
– V
OUT
MIN and MAX Test
The following two tests check V
OUT
min/max for the regulator with a 1K
Ω load. Exact
values may also be measures. Additional tests can be entered to test the regulator
under other load conditions. Use R
GK
load on the 5000 Series Tester front panel for
any loads not supplied internally. To test V
O
of 5V with a 5mA load, make the
following entries:
Test 1:
V
OUT
> 4.9V
I
MAX
= 50mA (limit current)
V
IN
= 10V
LOAD = 1K
Ω (internal) or program electronic load = 5mA
Test 2:
VOUT < 5.1V
IMAX = 50mA (limit current)
VOUT VIN
ADJ
R1
R2
VREF
VOUT
LM317