1/16
October 2003
s
TYPICAL DROPOUT 1.3V (AT 3A)
s
THREE TERMINAL ADJUSTABLE OR FIXED
OUTPUT VOLTAGE 1.5V, 1.8V, 2.5V, 2.85V,
3.3V, 3.6V, 5V, 8V, 9V, 12V.
s
GUARANTEED OUTPUT CURRENT UP TO
3A
s
OUPUT TOLERANCE
2% AT 25C AND
3% IN FULL TEMPERATURE RANGE
s
INTERNAL POWER AND THERMAL LIMIT
s
WIDE OPERATING TEMPERATURE RANGE
-40C TO 125C
s
PACKAGE AVAILABLE: DPAK
s
PINOUT COMPATIBILITY WITH STANDARD
ADJUSTABLE VREG
DESCRIPTION
The LD1085 is a LOW DROP Voltage Regulator
able to provide up to 3A of Output Current.
Dropout is guaranteed at a maximum of 1.5V at
the maximum output current, decreasing at lower
loads. The LD1085 is pin to pin compatible with
the older 3-terminal adjustable regulators, but has
better performances in term of drop and output
tolerance.
A 2.85V output version is suitable for SCSI-2
active termination. Unlike PNP regulators, where
a part of the output current is wasted as quiescent
current, the LD1085 quiescent current flows into
the load, so increase efficiency. Only a 10F
minimum capacitor is need for stability.
The device is supplied in DPAK. On chip trimming
allows the regulator to reach a very tight output
voltage tolerance, within 2% at 25C.
LD1085C
SERIES
3A LOW DROP POSITIVE VOLTAGE
REGULATOR ADJUSTABLE AND FIXED
SCHEMATIC DIAGRAM
DPAK
LD1085C SERIES
2/16
ABSOLUTE MAXIMUM RATINGS
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is
not implied.
THERMAL DATA
APPLICATION CIRCUITS
Symbol
Parameter
Value
Unit
V
I
DC Input Voltage
30
V
I
O
Output Current
Internally Limited
mA
P
D
Power Dissipation
Internally Limited
mW
T
stg
Storage Temperature Range
-55 to +150
C
T
op
Operating Junction Temperature Range
-40 to +125
C
Symbol
Parameter
DPAK
Unit
R
thj-case
Thermal Resistance Junction-case
3
C/W
R
thj-amb
Thermal Resistance Junction-ambient
62.5
C/W
R
2
V
O
= V
REF
(1 +
)
R
1
LD1085C SERIES
3/16
CONNECTION DIAGRAM (top view)
ORDERING CODES
(*) Available in Tape & Reel with the suffix "R" for fixed version and "-R" for adjustable version.
DPAK
DPAK (*)
OUTPUT VOLTAGE
LD1085CDT15
1.5 V
LD1085CDT18
1.8 V
LD1085CDT25
2.5 V
LD1085CDT28
2.85 V
LD1085CDT33
3.3 V
LD1085CDT36
3.6 V
LD1085CDT50
5.0 V
LD1085CDT80
8.0 V
LD1085CDT90
9.0 V
LD1085CDT120
12.0 V
LD1085CDT
ADJ
LD1085C SERIES
4/16
ELECTRICAL CHARACTERISTICS OF LD1085CDT15 (V
I
=4.5V, C
I
= C
O
=10
F, T
A
= -40 to 125C,
unless otherwise specified.)
NOTE 1: See short-circuit current curve for available output current at fixed dropout.
ELECTRICAL CHARACTERISTICS OF LD1085CDT18 (V
I
=4.8V, C
I
= C
O
=10
F, T
A
= -40 to 125C,
unless otherwise specified.)
NOTE 1: See short-circuit current curve for available output current at fixed dropout.
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
V
O
Output Voltage
I
O
= 0 mA
T
J
= 25C
1.47
1.5
1.53
V
I
O
= 0 to 3A V
I
= 3.1 to 30V (note 1)
1.455
1.5
1.545
V
V
O
Line Regulation
I
O
= 0 mA
V
I
= 3.1 to 18V
T
J
= 25C
0.2
4
mV
I
O
= 0 mA
V
I
= 3.1 to 15V
0.4
4
mV
V
O
Load Regulation
I
O
= 0 to 3A T
J
= 25C
2
10
mV
I
O
= 0 to 3A
4
20
V
V
d
Dropout Voltage
I
O
=3 A
1.3
1.5
V
I
q
Quiescent Current
V
I
30V
5
10
mA
I
sc
Short Circuit Current
V
I
- V
O
= 5V
3.2
4.5
A
V
I
- V
O
= 25V
0.2
0.5
A
Thermal Regulation
T
A
= 25C, 30ms pulse
0.003
0.015
%/W
SVR
Supply Voltage Rejection
f = 120 Hz,
C
O
= 25
F, I
O
= 3A
V
I
= 7.5
3V
60
75
dB
eN
RMS Output Noise Voltage
(% of V
O
)
T
A
= 25C
f =10Hz to 10KHz
0.003
%
S
Temperature Stability
0.5
%
S
Long Term Stability
T
A
= 125C
1000Hrs
0.5
%
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
V
O
Output Voltage
I
O
= 0 mA
T
J
= 25C
1.764
1.8
1.836
V
I
O
= 0 to 3A V
I
= 3.4 to 30V (note 1)
1.746
1.8
1.854
V
V
O
Line Regulation
I
O
= 0 mA
V
I
= 3.4 to 18V
T
J
= 25C
0.2
4
mV
I
O
= 0 mA
V
I
= 3.4 to 15V
0.4
4
mV
V
O
Load Regulation
I
O
= 0 to 3A T
J
= 25C
2
10
mV
I
O
= 0 to 3A
4
20
V
V
d
Dropout Voltage
I
O
=3 A
1.3
1.5
V
I
q
Quiescent Current
V
I
30V
5
10
mA
I
sc
Short Circuit Current
V
I
- V
O
= 5V
3.2
4.5
A
V
I
- V
O
= 25V
0.2
0.5
A
Thermal Regulation
T
A
= 25C, 30ms pulse
0.003
0.015
%/W
SVR
Supply Voltage Rejection
f = 120 Hz,
C
O
= 25
F, I
O
= 3A
V
I
= 7.5
3V
60
75
dB
eN
RMS Output Noise Voltage
(% of V
O
)
T
A
= 25C
f =10Hz to 10KHz
0.003
%
S
Temperature Stability
0.5
%
S
Long Term Stability
T
A
= 125C
1000Hrs
0.5
%
LD1085C SERIES
5/16
ELECTRICAL CHARACTERISTICS OF LD1085CDT25 (V
I
=5.5V, C
I
= C
O
=10
F, T
A
= -40 to 125C,
unless otherwise specified.)
NOTE 1: See short-circuit current curve for available output current at fixed dropout.
ELECTRICAL CHARACTERISTICS OF LD1085CDT285 (V
I
=5.85V, C
I
= C
O
=10
F, T
A
= -40 to 125C,
unless otherwise specified.)
NOTE 1: See short-circuit current curve for available output current at fixed dropout.
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
V
O
Output Voltage
I
O
= 0 mA
T
J
= 25C
2.45
2.5
2.55
V
I
O
= 0 to 3A V
I
= 4.1 to 30V (note 1)
2.425
2.5
2.575
V
V
O
Line Regulation
I
O
= 0 mA
V
I
= 4.1 to 18V
T
J
= 25C
0.2
5
mV
I
O
= 0 mA
V
I
= 4.1 to 18V
0.4
5
mV
V
O
Load Regulation
I
O
= 0 to 3A T
J
= 25C
2
10
mV
I
O
= 0 to 3A
4
20
V
V
d
Dropout Voltage
I
O
=3 A
1.3
1.5
V
I
q
Quiescent Current
V
I
30V
5
10
mA
I
sc
Short Circuit Current
V
I
- V
O
= 5V
3.2
4.5
A
V
I
- V
O
= 25V
0.2
0.5
A
Thermal Regulation
T
A
= 25C, 30ms pulse
0.008
0.04
%/W
SVR
Supply Voltage Rejection
f = 120 Hz,
C
O
= 25
F, I
O
= 3A
V
I
= 7.5
3V
60
72
dB
eN
RMS Output Noise Voltage
(% of V
O
)
T
A
= 25C
f =10Hz to 10KHz
0.003
%
S
Temperature Stability
0.5
%
S
Long Term Stability
T
A
= 125C
1000Hrs
0.5
%
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
V
O
Output Voltage
I
O
= 0 mA
T
J
= 25C
2.793
2.85
2.907
V
I
O
= 0 to 3A V
I
= 4.5 to 30V (note 1)
2.765
2.85
2.935
V
V
O
Line Regulation
I
O
= 0 mA
V
I
= 4.5 to 18V
T
J
= 25C
0.2
6
mV
I
O
= 0 mA
V
I
= 4.5 to 18V
0.5
6
mV
V
O
Load Regulation
I
O
= 0 to 3A T
J
= 25C
3
15
mV
I
O
= 0 to 3A
7
20
V
V
d
Dropout Voltage
I
O
=3 A
1.3
1.5
V
I
q
Quiescent Current
V
I
30V
5
10
mA
I
sc
Short Circuit Current
V
I
- V
O
= 5V
3.2
4.5
A
V
I
- V
O
= 25V
0.2
0.5
A
Thermal Regulation
T
A
= 25C, 30ms pulse
0.008
0.04
%/W
SVR
Supply Voltage Rejection
f = 120 Hz,
C
O
= 25
F, I
O
= 3A
V
I
= 7.85
3V
60
72
dB
eN
RMS Output Noise Voltage
(% of V
O
)
T
A
= 25C
f =10Hz to 10KHz
0.003
%
S
Temperature Stability
0.5
%
S
Long Term Stability
T
A
= 125C
1000Hrs
0.5
%
PDF 
ZIP