Page 1
3 A low-drop, adjustable positive voltage regulator
Features
■ Typical dropout 1.3 V (at 3 A)
■ Three terminal adjustable output voltage
■ Guaranteed output current up to 3 A
■ Output tolerance ± 2 % at 25 °C and ± 3 % in
full temperature range
■ Internal power and thermal limit
■ Wide operating temperature range -40 °C to
125 °C
■ Package available: DPAK
■ Pinout compatibility with standard adjustable
VREG
Description
LD1085CXX
DPAK
The LD1085C is a low drop voltage regulator able
to provide up to 3 A of output current. Dropout is
guaranteed at a maximum of 1.5 V at the
maximum output current, decreasing at lower
loads. The LD1085C is pin to pin compatible with
the older 3-terminal adjustable regulators, but has
better performances in term of drop and output
tolerance.
A 2.85 V 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 LD1085C quiescent current flows into
the load, so increase efficiency. Only a 10 µF
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 25 °C.
Table 1. Device summary
Order codes Packages
LD1085CDT-R DPAK (tape and reel)
April 2008 Rev 8 1/16
www.st.com
16
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Contents LD1085CXX
Contents
1 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Schematic application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
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LD1085CXX Diagram
1 Diagram
Figure 1. Schematic diagram
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Pin configuration LD1085CXX
2 Pin configuration
Figure 2. Pin connections (top view)
DPAK
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LD1085CXX Maximum ratings
3 Maximum ratings
Table 2. Absolute maximum ratings
Symbol Parameter Value Unit
DC input voltage 30 V
Output current Internally limited
Power dissipation Internally limited
Storage temperature range -55 to +150 °C
Operating junction temperature range -40 to +125 °C
T
P
T
V
I
I
O
D
STG
OP
Note: Absolute maximum ratings are those values beyond which damage to the device may occur.
Functional operation under these condition is not implied.
Table 3. Thermal data
Symbol Parameter DPAK Unit
R
R
thJC
thJA
Thermal resistance junction-case 3 °C/W
Thermal resistance junction-ambient 62.5 °C/W
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Page 6
Schematic application LD1085CXX
4 Schematic application
Figure 3. Application circuit
R
2
VOV
⎛⎞
1
⋅=
REF
⎝⎠
------ -+
R
1
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LD1085CXX Electrical characteristics
5 Electrical characteristics
Table 4. Electrical characteristics of LD1085CDT
(V
= 4.25 V, CI = CO =10 µF, TA = -40 to 125 °C, unless otherwise specified).
I
Symbol Parameter Test condition Min. Typ. Max. Unit
V
ΔV
ΔV
V
I
O(min)
Output voltage
O
Line regulation
O
Load regulation
O
Dropout voltage IO = 5A 1.3 1.5 V
d
(1)
Minimum load current VI = 30V 3 10 mA
IO = 10mA TJ = 25°C 1.225 1.25 1.275 V
I
= 10mA to 3A, VI = 2.85 to 30V
O
= 10mA, VI = 2.85 to 16.5V,
I
O
TJ = 25°C
I
= 10mA, VI = 2.85 to 16.5V 0.035 0.2 %
O
I
= 10mA to 5A, TJ = 25°C 0.1 0.3 %
O
= 0 to 5A 0.2 0.4 %
I
O
(1)
1.213 1.25 1.288 V
0.015 0.2 %
VI - VO = 5V 3.2 4.5 A
I
Short circuit current
sc
Thermal regulation T
SVR Supply voltage rejection
I
ΔI
eN
Adjust pin current VI = 4.25V, IO = 10 mA 55 120 µA
ADJ
Adjust pin current change IO = 10mA to 3A, VI = 2.75 to 16.5V
ADJ
RMS output noise voltage
(% of V
)
O
- VO = 25V 0.2 0.5 A
V
I
= 25°C, 30ms pulse 0.003 0.015 %/W
A
f = 120 Hz, C
IO = 3A, VI = 6.25 ± 3V
T
= 25°C, f =10Hz to 10kHz 0.003 %
A
= 25µF,C
O
= 25 µF,
ADJ
(1)
60 75 dB
0.2 5 µA
S Temperature stability 0.5 %
S Long term stability T
1. See short-circuit current curve for available output current at fixed dropout.
= 125°C, 1000Hrs 0.5 %
A
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Typical application LD1085CXX
6 Typical application
(Unless otherwise specified TJ = 25 °C, CI = CO = 10 µF)
Figure 4. Output voltage vs temperature Figure 5. Output voltage vs temperature
Figure 6. Output voltage vs temperature Figure 7. Short circuit current vs dropout
voltage
Figure 8. Line regulation vs temperature Figure 9. Load regulation vs temperature
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LD1085CXX Typical application
Figure 10. Dropout voltage vs temperature Figure 11. Dropout voltage vs output current
Figure 12. Adjust pin current vs temperature Figure 13. Quiescent current vs temperature
Figure 14. Line regulation vs temperature Figure 15. Supply voltage rejection vs output
current
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Typical application LD1085CXX
Figure 16. Supply voltage rejection vs
frequency
Figure 18. Minimum load current vs
temperature
Figure 17. Supply voltage rejection vs
temperature
Figure 19. Stability
Figure 20. Stability Figure 21. Line transient
VI=12 to 13V, IO=200mA, CI = 1µF(tant), CO=10µF(tant),
C
=1µF
ADJ
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LD1085CXX Typical application
Figure 22. Line transient Figure 23. Load transient
VI=12 to 13V, IO=200mA, CI = 1µF(tant), CO=10µF(tant),
Figure 24. Load transient
VI=12V, IO=0.12 to 3A, CI = 1µF(tant), CO=10µF(tant),
=1µF
C
ADJ
C
=1µF
ADJ
VI=12V, IO=0.12 to 3A, CI = 1µF(tant), CO=10µF(tant),
=1µF
C
ADJ
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Package mechanical data LD1085CXX
7 Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK®
packages. These packages have a lead-free second level interconnect. The category of
second Level Interconnect is marked on the package and on the inner box label, in
compliance with JEDEC Standard JESD97. The maximum ratings related to soldering
conditions are also marked on the inner box label. ECOPACK is an ST trademark.
ECOPACK specifications are available at: www.st.com.
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LD1085CXX Package mechanical data
DPAK mechanical data
Dim.
Min. Typ. Max. Min. Typ. Max.
A 2.2 2.4 0.086 0.094
A1 0.9 1.1 0.035 0.043
A2 0.03 0.23 0.001 0.009
B 0.64 0.9 0.025 0.035
b4 5.2 5.4 0.204 0.212
C 0.45 0.6 0.017 0.023
C2 0.48 0.6 0.019 0.023
D 6 6.2 0.236 0.244
D1 5.1 0.200
E 6.4 6.6 0.252 0.260
E1 4.7 0.185
e2.28 0.090
e1 4.4 4.6 0.173 0.181
H 9.35 10.1 0.368 0.397
L 1 0.039
(L1)
L2 0.8 0.031
L4 0.6 1 0.023 0.039
R 0.2 0.008
V2 0° 8°0° 8°
mm. inch.
2.8 0.110
0068772-F
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Package mechanical data LD1085CXX
Tape & reel DPAK-PPAK mechanical data
Dim.
Min. Typ. Max. Min. Typ. Max.
A 330 12.992
C12.8 13.0 13.2 0.504 0.512 0.519
D 20.2 0.795
N60 2.362
T22.40.882
Ao 6.806.90 7.00 0.268 0.272 0.2.76
Bo 10.40 10.50 10.60 0.409 0.413 0.417
Ko 2.55 2.65 2.75 0.100 0.104 0.105
Po 3.9 4.0 4.1 0.153 0.157 0.161
P7.98.0 8.1 0.311 0.315 0.319
mm. inch.
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LD1085CXX Revision history
8 Revision history
Table 5. Document revision history
Date Revision Changes
07-Oct-2004 6 Mistake in Table 1.
03-Jul-2007 7 Order codes updated.
09-Apr-2008 8 Modified: Table 1 on page 1.
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LD1085CXX
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