PL1084-XXXJ3 Datasheet, PDF (3/6 Pages) Cystech Electonics Corp. – 5A Low Dropout Positive Voltage Regulator

Spec. No. : C512J3
CYStech Electronics Corp. Issued Date : 2007.07.04
Revised Date :
Page No. : 3/6
Note: 1. See thermal regulation specifications for changes in output voltage due to heating effects. Line and load regulation are
measured at a constant junction temperature by low duty cycle pulse testing. Load regulation is measured at the output
lead =1/18” from the package.
2. Line and load regulation are guaranteed up to the maximum power dissipation of 15W. Power dissipation is determined
by the difference between input and output and the output current. Guaranteed maximum power dissipation will not be
over the full input/output range.
Block Diagram
Functional Description
Introduction
The PL1084 adjustable Low Dropout(LDO) regulator is a 3 terminal device that can easily be programmed with the
addition of two external resistors to any voltages within the range of 1.25V to 2.5V. The PL1084 only needs 1.5V
differential between Vin and Vout to maintain output regulation. In addition, the output voltage tolerances are also
extremely tight and they include the transient response as part of the specification. For example, Intel VRE
specification calls for a total of ±100mV including initial tolerance, load regulation and 0 to 5A load step. The
PL1084 is specifically designed to meet the fast current transient needs as well as providing an accurate initial voltage,
reducing the overall system cost with the need for fewer output capacitors.
Output Voltage Setting
The PL1084 can be programmed to any voltages in the range of 1.25V to 5V with the addition of R1 and R2 external
resistors according to the following formula:
Vout=Vref(1+R2/R1)+Iadj*R2, where Vref=1.25V typically, Iadj=55μA typically
The PL1084 keeps a constant 1.25V between the output pin and the adjust pin. By placing a resistor R1 across these
two pins, a constant current flows through R1, adding to the Iadj current requirement of the PL1084. R1 is typically
selected to be 121Ω resistor so that it automatically satisfies the minimum current requirement. Notice that since
Iadj is typically in the range of 55μA, it only adds a small error to the output voltage and should only be considered
when a very precise output voltage setting is required. For example, in a typical 3.3V application where R1=121Ω
and R2=200Ω, the error due to Iadj is only 0.3% of the nominal set point.
PL1084-XXXJ3
CYStek Product Specification