PL317E3 Datasheet, PDF (5/9 Pages) Cystech Electonics Corp. – Three Terminal Adjustable Output Positive Voltage Regulators

24V
14V
f=120Hz
CYStech Electronics Corp.
Spec. No. : C513E3
Issued Date : 2003.04.09
Revised Date : . .
Page No. : 5/9
Vin
PL317
Vout
Adjust
R1
1%
Cin 0.1^μF
D1 *
1N4002
+ _{1μF RL}
Co
Vout=10V
Vo
CAdj ⁺ 10^μF
R2
1%
* D1 Discharges CAdj if output is shorted to ground
Fig 4. Ripple Rejection Test Circuit
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 1+R2/R1)+IAdjR2
Since the current from the adjustment terminal (IAdj) represents an error term in the equation, the PL317
was designed to control IAdj to less than 100 µA and keep it constant. To do this, all quiescent operating
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.
Vin
PL317
Adjust
Vout
Vref
IAdj
Vref=1.25V typical
Vout
R1
Iprog
R2
Fig 5. Basic Circuit Configuration
PL317E3
CYStek Product Specification