Ap1086 – Diodes AP1086 User Manual
Page 4
AP1086
1.5A LOW DROPOUT POSITIVE ADJUSTABLE OR
FIXED-MODE REGULATOR
AP1086
Document number: DS31028 Rev. 6 - 2
4 of 10
June 2010
© Diodes Incorporated
Functional Description
Introduction
The AP1086 adjustable or fixed-mode Low Dropout (LDO) regulator is a 3 terminal device which can easily be
programmed by internal mask change to any voltages within the range of 1.25V to V
IN
-1.4V. The AP1086 only
needs 1.4V differential between V
IN
and V
OUT
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
1.5A load step.
The AP1086 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 AP1086 is only a 3 terminal device, it is not possible to provide true remote sensing of the 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 AP1086 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 10uF aluminum electrolytic capacitor insures both stability
and good transient response.
Thermal Design
The AP1086 incorporates an internal thermal 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
o
C, 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 V
OUT
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 V
OUT
pin to the output capacitors to prevent
any high frequency oscillation that may result due to excessive trace inductance.