APL158115FC-TRL ANPEC [Anpec Electronics Coropration], APL158115FC-TRL Datasheet - Page 9

• Manufacturer Part Number: APL158115FC-TRL
• Description: DUAL INPUT LOW DROPOUT REGULATOR
• Manufacturer: ANPEC [Anpec Electronics Coropration]

APL1581
Application Information (Cont.)
Output Voltage Setting (Cont.)
grammable to any voltages in the range of 1.25V to 5.
according to the following formula:
The recommended R1 is in range of 100 to125 to
satisfy the minimum load current requirement. Proper
sizes of R2 and R1 are also concerned for power
dissipation.
Grounding and Output Sensing
The APL1581 allows true Kelvin sensing for both the
high and low side of the load. Figure 2 shows the de-
vice connected to take advantage of the remote sense
feature. The SENSE pin and the top of the resistor
divider are connected to the top of the load; the bot-
tom of the resistor divider is connected to the bottom
of the load. Typically the load is a microprocessor
and parasitic resistance RP is made up of the PC traces
and /or connector resistance between the regulator
and the processor. RP is now connectedinside the
regulation loop of the APL1581 and for reasonable val-
ues of RP the load regulation at the load will be
negligible. Voltage drops due to RP are not eliminated;
they will add to the dropout voltage of the regulator
Copyright
Rev. B.5 - Mar., 2008
V
V
V
where V
OUT
CNT L
CNT L
V
V
IN
IN
Figure 1 Setting Output Voltage
Figure 1 Setting Output Voltage
= V
I
ADJ
REF
REF
ANPEC Electronics Corp.
= 50 A (typical)
x (1+
= 1.25V (typical)
VCNTL
VCNTL
VIN
VIN
APL1581
APL1581
R2
R1
AD J
AD J
VSENSE
VSENSE
I
I
A DJ
A DJ
VOU T
VOU T
) + I
=50uA
=50uA
ADJ
V
V
RE F
RE F
x R2
R1
R1
R 2
R 2
V
V
OUT
OUT
5V
9
regardless of whether they are inside or outside the
regulation loop.
Stability and Output Capacitors
The circuit design of using the APL1581 series re-
quires an output capacitor as part of the device fre-
quency compensation. The following chart shows a
stable region to select output capacitor for APL1581.
This region above the curve indicates minimum re-
quired ESR and capacitance to maintain stability.
However, the output capacitor should have an ESR
less than1 .
V
V
V
V
CNTL
CNTL
CNTL
CNTL
V
V
V
V
IN
IN
IN
IN
100
100
80
80
60
60
40
40
20
20
0
0
Figure 2 Remote Voltage Sensing
Figure 2 Remote Voltage Sensing
1
1
VCN TL
VCN TL
VCN TL
VCN TL
VIN
VIN
VIN
VIN
Fixed Voltage
Fixed Voltage
Adjustable
Adjustable
Device
Device
Device
Device
APL1581
APL1581
APL1581
APL1581
GN D
GN D
AD J
AD J
Capacitance( F)
Capacitance( F)
VSENSE
VSENSE
VSENSE
VSENSE
10
10
VOU T
VOU T
VOU T
VOU T
Stable Region
Stable Region
100
100
R1
R1
R 2
R 2
www.anpec.com.tw
R P
R P
R P
R P
1000
1000
V
V
V
V
OUT
OUT
OUT
OUT
Load
Load
Load
Load