LM317A
APPLICATION CIRCUITS
V
IN
3
LINEAR INTEGRATED CIRCUIT
UTC LM317A
I
ADJ
1
2
V
OUT
D1 1N4002
R1
Co
1μF
C1
0.1μF
V
IN
3
UTC
LM317A
1
2
120Ω
1kΩ
V
OUT
1μF
R2
720Ω
V
OUT
=1.25V×(1+R2/R1)+I
ADJ
×R2
C1 is required when regulator is located an
appreciated distance from power supply. Co is
needed to improve transient response.
Fig.1 Programmable voltage regulator
TTL Level
signal
Fig.2 Regulator with On-off control
1.25 V
V
REF
) + I
ADJ
=
R1
R1
V
REF
1.25 V
I
O(MIN)
= (
) + I
ADJ
=
R1+ R2
R1+ R2
5mA < I
OUT
< 100mA
I
O(MAX )
= (
Fig.3 Soft Start Application
Fig.4 Constant Current Application
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
4 of 5
QW-R101-026.D