LM317M
+25V
V
in
Adjust
* To provide current limiting of I
O
to the system ground, the source of
the current limiting diode must be tied to
a negative voltage below −7.25 V.
V
ref
R
2
≥
I
DSS
R
1
=
V
ref
I
Omax
+ I
DSS
LM317M
V
out
R
1
1.25k
D1
1N914
D2
1N914
V
in
V
O
I
O
D
1
1N4002
V
in
LM317M
V
out
+
120
1N5314
Adjust
MPS2222
720
V
SS
*
1.0k
TTL
Control
1.0mF
V
out
R
2
500
Minimum V
out
= 1.25 V
V
O
< P
OV
+ 1.25 V + V
SS
I
Lmin
− I
P
< I
O
< 500 mA − I
P
As shown O < I
O
< 495 mA
D
1
protects the device during an input short circuit.
Figure 21. Adjustable Current Limiter
Figure 22. 5 V Electronic Shutdown Regulator
V
in
LM317M
V
out
V
out
240
1N4001
V
in
LM317M
R
1
V
out
I
Adj
R
2
I
out
Adjust
Adjust
R
2
MPS2907
50k
+
10mF
I
outmax
=
V
ref
R
1
+ R
2
1.25 V
+ I
Adj
^
R + R
1
2
5.0 mA < I
out
< 100 mA
Figure 23. Slow Turn−On Regulator
Figure 24. Current Regulator
R
θ
JA, THERMAL RESISTANCE, JUNCTION−TO−AIR (
°
C/W)
100
90
80
70
60
50
R
qJA
40
0
5.0
10
15
20
25
30
L, LENGTH OF COPPER (mm)
Minimum
Size Pad
Free Air
Mounted
Vertically
P
D(max)
for T
A
= 50°C
2.4
2.0
2.0 oz. Copper
L
L
1.6
1.2
0.8
0.4
0
280
240
200
160
120
80
R
qJA
40
0
5.0
10
15
20
Minimum
Size Pad
Free Air
Mounted
Vertically
P
D(max)
for T
A
= 50°C
2.50
1.25
2.0 oz. Copper
L
0.83
0.63
0.50
0.42
0.35
L, LENGTH OF COPPER (mm)
Figure 25. DPAK Thermal Resistance and Maximum
Power Dissipation versus PCB Copper Length
Figure 26. SOT−223 Thermal Resistance and Maximum
Power Dissipation versus PCB Copper Length
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