CYStech Electronics Corp.

Spec. No. : C513F3

Issued Date : 2003.05.24

Revised Date :

. .

Page No. : 5/9

PL317F3

CYStek Product Specification

+

Cin

0.1μF

Adjust

Vin

Vout

PL317

R2

1%

R1

1%

Co

1μF

RL

Vo

+

D1 *

CAdj

10μF

1N4002

Vout=10V

* D1 Discharges CAdj if output is shorted to ground

24V

14V

f=120Hz

Application Information

Basic Circuit Operation

The PL317 is a 3-terminal floating regulator. In operation, the PL317 develops and maintains a nominal

1.25V reference (Vref) between its output and adjustment terminals. This reference voltage is converted

to a programming current (Iprog) by R1(see Fig 5), and this constant current flows through R2 to ground.

The regulated output voltage is given by:

Vout=Vref

current is returned to the output terminal. This imposes the requirement for a minimum load current. If

the load current is less than this minimum, the output voltage will rise.

Since the PL317 is a floating regulator, it is only the voltage differential across the circuit which is

important to performance, and operation at high voltages with respect to ground is possible.

R1

R2

Vout

Adjust

Vin

Vout

IAdj

PL317

Iprog

Vref

Vref=1.25V typical

Fig 4. Ripple Rejection Test Circuit

Fig 5. Basic Circuit Configuration