PL1085-XXXFP Datasheet, PDF (3/5 Pages) Cystech Electonics Corp. – 3A Low Dropout Positive Voltage Regulator

Block Diagram
Spec. No. : C540FP
CYStech Electronics Corp. Issued Date : 2007.07.04
Revised Date :
Page No. : 3/5
Functional Description
Introduction
The PL1085 adjustable or fixed-mode Low Dropout(LDO) regulator is a 3 terminal device which can easily be
programmed by internal mask change to any voltage within the range of 1.25V to Vin-1.4V. The PL1085 only needs
1.4V 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 3A load step. The
PL1085 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.
Load Regulation
Since the PL1085 is only a 3 terminal device, it is not possible to provide true remote sensing of output voltage at the
load. But it can supply good load regulation by internal feedback bypass the external loss such as adjustable mode.
Stability
The PL1085 requires the use of an output capacitor as part of the frequency compensation in order to make the
regulator stable. For most applications, a minimum of 10μF aluminum electrolytic capacitor insures both stability
and good transient response.
Thermal Design
The PL1085 incorporates an internal shutdown that protects the device when the junction temperature exceeds the
maximum allowable junction temperature. Although this device can operate with junction temperatures in the range
of 150℃, it is recommended that the selected heat sink be chosen such that during maximum continuous load
operation, the junction temperature is kept below the temperature.
Layout Consideration
The output capacitors must be located as close to the Vout terminal of the device as possible. It is recommended to
use a section of a layer of the PC board as a plane to connect the Vout pin to the output capacitors to prevent any high
frequency oscillation that may result due to excess trace inductance.
PL1085-XXXFP
CYStek Product Specification